IX science
AJAY PARMAR
1
GROUP TUITION
Chapter – 4, chemical bonding
Chemical Bonds:
The force of attraction between the atoms of a molecule, which keeps them
bonded together, is known as a chemical bond.
Octet State:
When the atoms of an element exchange or share their valence electrons with one
or more atoms, it results in the configuration of octet and achieves an inert gas
configuration.
Octet Rule:
When the atoms of an element exchange or share their valence electrons with one
or more atoms, it results in the formation of octet and achieves an inert gas
configuration.
Ion:
When an atom of an element accepts or loses electron it gets the stable electron
configuration like that of inert gas. Now it is called an ion.
Ionic Bond:
There is an attractive force between the ions having opposite electrical charges
and stable configuration and a bond is formed. This bond is known as ionic bond.
Cation (positive ion):
When atom of an element loses electrons from its outermost orbit, it forms a
cation (positive ion).
Anion (negative ion):
When an atom of an element gains electron/s in its outermost orbit it forms an
anion (negative ion).
Covalent Bond:
The bond formed between the two atoms by sharing electrons is known as
covalent bond.
Bonding pair of electrons:
When two atoms of an element share the electrons equally, sharing electron pair is
known as bonding electron pair.
Valence:
The number of electrons an atom gains, loses or shares to form a bond with other
element is known as the valence of an atom.
Polar Covalent Bond:
In a diatomic molecule, if both the atoms are of different elements, then the
sharing electron pair will be attracted more towards the atom, which has higher
electronegativity. As a result the electron pair will be attracted more towards the
atom having higher electronegativity. Covalent bond formed in this way is called
a polar covalent bond.
Electronegativity:
The tendency of an atom to attract the bonding electron pair between two atoms
of a molecule is known as electro-negativity.
1.







2.


What is a chemical bond? Explain its types giving one example of each.
Chemical bond is a strong force of attraction which keeps two or more atoms bonded together.
The two types of chemical bonds are (i) Ionic bond and (ii) Covalent bond.
Ionic bond:
Ionic bond is formed due to the strong attraction forces between oppositely charged ions.
During the formation of ionic bond there is transfer of electrons from one atom to the other.
e.g. NaCl and MgCl2 are formed due to ionic bonds.
Covalent bonds:
This chemical bond is formed due to sharing of valence electrons between the atoms.
e.g. H2, N2, O2, H2O, etc are formed due to covalent bond.
What is an ion? Explain the formation of both types of ions.
When an atom of an element accepts or loses electron it gets the stable electron configuration like that of
nearest inert gas and forms an ion
Two types of ions: (1) Positive ion or Cation and (2) Negative ion or Anion.
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Sodium atom
(2,8,1)
Chlorine atom
(2, 8, 7)
3.







positive sodium ion
(2,8) electronic configuration same as that of Neon
When an atom of an element gains electrons in its outermost orbit it forms an anion
Atomic number of Cl = 17 E. C = 2, 8, 7  7 electrons in valence orbit
It gains one electron, and forms a negative chloride ion
Cl
+
e–

Cl–
Chlorine atom
(2, 8, 7)

negative chloride ion
(2, 8, 8) electronic configuration same as that of Argon
When sodium and chlorine atoms come closer to each other, sodium donates its one electron to chlorine
atom and forms sodium ion and chloride ion
Due to the opposite electrical charges and stable configuration, they form an ionic bond
Na
+
½Cl2

Na+ +
Cl–
Na+
+
Cl–

Na+Cl– (i.e. NaCl)
Thus ionic pair Na+Cl is formed, which is known as sodium chloride (NaCl)


4.

negative chloride ion
(2,8, 8) electronic configuration same as that of Argon
What is ionic bond? Explain the formation of sodium chloride.
Due to the opposite electrical charges and stable configuration, there arises an attractive force between the
ions. This is called ionic bond
There is an exchange of electrons between the atoms of elements during its formation
Formation of sodium chloride (NaCl) molecule
Atomic number of Na = 11
E. C = 2, 8, 1  one electron in its valence orbit
It loses this electron and forms a positive sodium ion
Na

Na+ +
e–
Sodium atom
(2,8,1)

positive sodium ion
(2,8) electronic configuration same as that of Neon
Formation of Negative ion or Anion
When an atom of an element gains electrons in its outermost orbit it forms an anion
Atomic number of Cl = 17 E. C = 2, 8, 7  7 electrons in valence orbit
It gains one electron, and forms a negative chloride ion
Cl
+
e–

Cl–





GROUP TUITION
Formation of positive ion or Cation
When atom of an element loses electrons from its outermost orbit, it forms a positive ion
Atomic number of Na = 11
E. C = 2, 8, 1  one electron in its valence orbit
It loses this electron and forms a positive sodium ion
Na

Na+ +
e–





2
Explain the formation of magnesium chloride.
Formation of magnesium chloride (MgCl2) molecule
Atomic number of Mg = 12 E. C. = 2, 8, 2
2 electrons in its valence orbit
It loses two electrons and forms a positive magnesium ion
Mg

Mg2+
+
2e–
Magnesium atom
(2, 8, 2)
positive magnesium ion
(2, 8) electronic configuration same as that of Neon
Chlorine atom
(2, 8, 7)
negative chloride ion
(2, 8, 8) electronic configuration same as that of Argon
Atomic number of Cl = 17 E. C. = 2, 8, 7  7 electrons in valence orbit
It gains one electron, and forms a negative chloride ion
Cl
+
e–

Cl–
When one atom of magnesium and two atoms chlorine come closer to each other, magnesium atom donates
two electrons to chlorine atoms (one electron to each)
Mg2+
+
2Cl–

MgCl2
Due to the opposite electrical charges and stable configuration, they form an ionic bond
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3
GROUP TUITION

Thus magnesium chloride (MgCl2) is formed
5.
Explain the formation of aluminium oxide.
Formation of Aluminium oxide (Al2O3) molecule
Atomic number of Al = 13 E. C. = 2, 8, 3
3 electrons in its valence orbit
It loses three electrons and forms a positive aluminium ion
Al

Al3+
+
3e–



Oxygen atom
(2, 6)
negative oxide ion
(2, 8) electronic configuration same as that of Argon
When two atoms of aluminium and three atoms oxygen come closer to each other, aluminium atoms donate
2 electrons to each of oxygen atoms.
2Al3+
+
3O2–

Al2O3.
Due to the opposite electrical charges and stable configuration, they form an ionic bond
Thus aluminium oxide (Al2 O3) is formed.
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6.
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7.
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8.
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9.
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
positive aluminium ion
(2, 8) electronic configuration same as that of Neon
Atomic number of O = 8 E. C. = 2, 6.  6 electrons in valence orbit
It gains two electrons, and forms a negative oxide ion
O
+
2e–

O2–



Aluminium atom
(2, 8, 3)
What are electropositive elements? Give examples.
Atoms of an elements having one, two or three electrons in its outermost orbit have a tendency to lose the
electrons
All metallic elements have one, two or three electrons in their valence orbit
Thus metallic elements have a tendency to form positive ions e.g., Na+, Mg2+, A13+, etc.
What are electronegative elements? Give examples.
Atoms of elements which have six to seven electrons in their outermost orbit have tendency to gain the
electrons
Non-metallic elements have six to seven electrons in their valence orbit
Thus non-metallic elements have a tendency to form negative ion
e.g. Cl, O2, etc
How do atoms combine to form a molecule?
It is essential to have octet in the outermost orbit for stability of an atom in a molecule
When an atom of an element has 1 to 7 electrons in its outermost orbit, it has a tendency to exchange or
share the electrons with the other atom to complete the octet
Energy decreases when chemical bond is formed between two atoms to form a molecule
This stabilizes the molecule
Thus, to get the stability, atoms combine to form a molecule.
Why are molecules more stable than an atom?
According to octet rule, when atoms of an element exchange or share their valence electrons with one or
more atoms, octet is formed.
During the formation of these molecules the energy of the bonding elements decrease.
This decrease in the energy stabilizes moecules.
Hence molecule is more stable than an atom.
10. Inert gases are non – reactive. Explain.
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


Chemical reactivity of element depends on the number of valence electrons.
If the atom of an element consists of incompletely filled valence orbit than it is reactive while if it is
completely filled then it is non – reactive.
Inert gas like He, Ne, Ar, Kr, Xe, etc. have their outermost orbits completely filled
So they do not show reactivity.
11. Differentiate between stability of sodium atom and sodium ion.
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4
GROUP TUITION
Electronic configuration of Na = 2, 8, 1 It has one electron in its incompletely filled valence orbit 
unstable.
Sodium atom loses one electron from its valence shell to form Na+ ion
Electronic configuration of Na+ is 2, 8, which resembles to that of an inert element neon and thus achieves
stability.
12. Common salt is harmless for edible purpose. Why?
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
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

In common salt i.e. sodium chloride Na+ and Cl are attached with each other by ionic bond.
Atom of sodium metal is chemically very reactive as its outermost orbit has 1 electron i.e. it is incompletely
filled.
Na+ is reactive with respect to its charge, but it is not reactive like sodium metal because of its stable
configuration.
Atom of chlorine gas is very reactive as its outermost orbit has 7 electrons i.e. incompletely filled.
Cl is reactive with respect to its charge, but it is not reactive like chlorine atom because of its stable
configuration.
Hence NaCl is safe to eat.
13. Explain the lattice structure of sodium chloride.


The lattice structure of sodium chloride is as shown in the following figure.
In a molecule of sodium chloride, there is Na+ ion and Cl ion
Sodium ion 
Chloride ion



In a crystal of sodium chloride:: one Na+ ion is surrounded by 6 Cl ions and one Cl ion is surrounded by
six Na+ ions
Due to this a maximum attraction is created between the oppositely charged ions and there is decrease in
energy of the crystal.
Due to this decrease in energy, stability is attained.
14. Write the properties of ionic compounds.
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Physical nature
Due to strong stable electric attraction between ions having opposite charges in an ionic compound in solid
state and crystalline.
They are hard.
They are brittle i.e. when pressure is applied they break down into smaller pieces.
Solubility
Generally they are water soluble as water decreases attraction between ions of ionic compounds
Insoluble in organic solvents like ether, carbon tetrachloride, alcohol, benzene, etc
Melting point and boiling point
In crystal structure of ionic compounds cations and anions are strongly attached to one another by inter ionic
attractive forces
In order to break these forces more energy is needed
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5
GROUP TUITION
So melting point and boiling points of ionic compounds are very high. (Ionic compounds have high
melting and boiling point. Explain.)
Electrical conductivity
In crystal structure of ionic compounds, the cations and anions are strongly attached to one another by inter
ionic attractive forces, so the ions cannot leave their places.
Therefore, ionic compounds in their solid state are non-conductor of electricity.(Why solid ionic
compounds are non-conductors?)
In aqueous solution or in a melted state of ionic compounds, the distance among the ions increases so the
attraction force among them decreases and ions can move freely.
Therefore, ionic compounds in aqueous solution or in a melted state are good conductors of electricity. (The
melted or aqueous ionic compounds are conductors of electricity. Why?)
15. What is a covalent bond?




The bond formed between the two atoms by sharing electrons is known as covalent bond.
When atoms can neither lose their valence electrons nor gain electrons, ionic bond cannot be formed.
Non – metals like hydrogen, chlorine, oxygen, nitrogen, etc cannot transfer electrons from their one atom to
another.
They combine with each other by sharing electrons i.e. by covalent bond.
16. Explain the formation covalent bonds in (i) Hydrogen moelcule, (ii) Chlorine molecule, (iii) Oxygen



molecule, (iv) Nitrogen molecule, (v) Ammonia molecule and (vi) Water molecule.
Hydrogen Molecule
Atomic number of hydrogen = 1 E. C. = 1
Valence orbit has 1 electron and so it requires one more electron to complete the duplet like that of helium
Hydrogen atoms share one pair of electrons and forms a single covalent bond



H
+ H

H : H or H – H (Draw diagram showing structure of hydrogen molecule.)
Chlorine molecule
Atomic number of chlorine = 17 E. C. = 2, 8, 7
Outer most orbit has 7 electron and so it requires one more electron to complete the octet like that of argon
Chlorine atoms share one pair of electrons and forms a single covalent bond

: Cl 








Cl – Cl
:O:





 : O :: O :
O=O
Nitrogen molecule
(Nitrogen is trivalent Explain.)
Atomic number of nitrogen = 7  E. C. = 2, 5
Thus its outer most orbit has 5 electrons and so it requires three more electrons to complete the octet like
that of neon
Nitrogen atoms share three pairs of electrons and form a triple covalent bond

N







+



Oxygen molecule
(Oxygen is divalent Explain.)
Atomic number of oxygen = 8  E. C. = 2, 6
Outer most orbit has 6 electrons and so it requires two more electron to complete the octet like that of neon
Oxygen atoms share two pairs of electrons and forms a double covalent bond
:O:



 Cl :  : Cl : Cl : or
+

+
N






N  N
NN
Ammonia molecule
Atomic number of nitrogen = 7  Electronic configuration = 2, 5
Atomic number of hydrogen = 1 Electronic configuration = 1
Thus valence orbit of nitrogen has 5 electrons while that of hydrogen has 1 electrons
So nitrogen requires three more electrons to complete the octet like that of neon and hydrogen requires one
more electron to complete the duplet like that of helium
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GROUP TUITION
Thus 1 atom of nitrogen shares 1 pair of electron with each of three atoms of hydrogen and forms three
single covalent bonds.
N

6
+

3 H



H  N
H

H
It can also be represented as H – N – H
|
H
Water molecule
Atomic number of oxygen = 8  Electronic configuration = 2, 6
Atomic number of hydrogen = 1 Electronic configuration = 1
Thus valence orbit of oxygen has 6 electrons while that of hydrogen has 1 electron.
So oxygen requires two more electrons to complete the octet like that of neon and hydrogen requires one
more electron to complete the duplet like that of helium
Thus 1 atom of oxygen shares 1 pair of electron with each of two atoms of hydrogen and forms two single
covalent bonds.

2 H
+
:O:


17. Draw diagram showing structure of hydrogen molecule.

Refer formation of hydrogen molecule in Q. 16
18. What are bonding pair of electrons?



Two atoms of share electrons from their valence orbit to form a molecule.
This sharing electron pair is known as bonding electron pair.
This bonding electron pair combines two atoms very firmly
19. Hydrogen and chlorine can form molecules but argon atoms do not form molecules. Why?








Hydrogen
Hydrogen atom has only one orbit and one electron
Two atoms of hydrogen, each sharing one electron forms a saturated configuration like helium to form
hydrogen molecule
Chlorine
The electron configuration of chlorine is 2, 8, 7
Two atoms of chlorine, each sharing one electron completes the octet structure and forms chlorine molecule
Argon
The electronic configuration of Argon is 2, 8, 8
The outermost orbit of Argon atom is saturated with electrons so the atom is stable
Thus, Argon atom has no tendency to exchange or to share electrons
Therefore, Argon molecule cannot be formed by two atoms of Argon
20. What is electronegativity? State its importance in chemical bonding.



The tendency of an atom to attract the bonding electron pair between two atoms of a molecule is known as
electro-negativity
If the difference in electronegativity of a bonded atom increases, the polar character of the covalent bond
increases
If the difference in electronegativity between the two bonded atoms is increased beyond certain limit, then
instead of covalent bond, it forms ionic bond
21. What is a polar covalent bond? Explain this bond with examples.


In a diatomic molecule, if both the atoms are of different elements, then the sharing electron pair will be
attracted more towards the atom, which has higher electronegativity
Covalent bond formed in this way is called a polar covalent bond
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7
GROUP TUITION
e.g. hydrogen chloride, the bonding electron pair is nearer to chlorine atom because chlorine has higher
electro-negativity
The bonded electron pair remain more attracted towards the chlorine atom and hydrogen atom attains partial
positive charge as compared to chlorine atom
The electrical charge is very small and it is represented by 
To show a polar covalent bond a sign + is given to one which is a partial positive charge.
A half way arrow ( ) moving from a partial positive charged element towards the partial negative
charged element is shown

H
 Cl :
+


δ
δ
H – Cl
22. Write the properties of covalent compounds.




Properties of compounds containing covalent bonds
Physical nature
Solid, liquid or gaseous state
Solubility
Usually soluble in solvents like ether, benzene, etc. but insoluble in solvent as water
Melting point and boiling point
Generally lower melting and boiling points, because atoms in molecules of covalent bonded compounds are
weakly bonded as compared to those in ionic compounds
Electrical conductivity
Poor conductors of electricity as there are no ions or free electrons responsible for electrical conduction.
23. A molecule can have both ionic as well as covalent bond. Explain giving examples.



When a positive ion combines with a negative ion having 2 or more atoms, a compound having both ionic
and covalent bond is formed.
e.g. sodium hydroxide, hydrogen cyanide, sulphuric acid, calcium carbonate, potassium permanganate,
ammonium nitrate etc
Sodium hydroxide
There are 6 electrons in the outermost orbit of oxygen and there is one electron in the outermost orbit of H
atom. These two atoms form a single covalent bond by sharing on electron each forming (OH)– ion

H +

:O:



: O :H


Hydrogen atom attains duplet stable configuration but oxygen atom requires one electron to complete the
octet,
It accepts this one electron from sodium atom
Na

Na+ +
e–


 :  : 
: O :H
+
e

 O H 

Thus there is an ionic bond between Na+ and (OH)–.
Similarly in hydrogen cyanide, there is an ionic bond between H+ and CN– ion while C and N are bonded
with triple covalent bond.
H+ + (CN)–  H+(CN)–.


–
24. What is called hydrogen bond? Explain the formation of hydrogen bond in HF and H2O. State their


properties.
When in a polar covalent bond, the electronegativity of hydrogen is less than that of the other atom attached
with it, the hydrogen atom gets a partial positive charge (+) on it
e.g. hydrogen fluoride (HF) and water (H2O)
Hydrogen bond in hydrogen fluoride
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AJAY PARMAR
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GROUP TUITION
The electronegativity of F is more than that of H in HF molecule
The electron pair of covalent bond is more attracted towards F partial positive charge + on hydrogen and
partial negative charge  on F
Two or more molecules of hydrogen fluoride remains attracted towards each other and remain near each
other because F has three non-bonding electron pairs
This type of attractive force is called hydrogen bond
Hydrogen bond is shown by dotted line (………)
Hydrogen bond in water



The electronegativity of O is more than that of H in H2O molecule
The electron pair of covalent bond is more attracted towards O resulting in partial positive charge + on
hydrogen and partial negative charge  on O
Hydrogen bond is shown by dotted line (………)
25. Mention bonds present in water and hydrogen fluoride and draw its figure.

Refer Q. 25.
26. Water steadily exists on earth. Explain.




There are hydrogen bonds in water molecules
Water in liquid state is not in free molecular state
As there is a formation of a weak H-bond in water, its evaporation is slow at room temperature
This way water steadily remains on earth
27. Identify the chemical bond in the molecules/compounds of the following: Hydrogen, Oxygen,







Nitrogen, Iodine, Sodium chloride, Magnesium chloride, Sodium fluoride, Water, Hydrogen fluoride,
Hydrogen chloride, Potassium bromide.
Hydrogen :: Single covalent bond
 Water :: Polar covalent bond and hydrogen
Oxygen :: Double covalent bond
bond
Nitrogen :: Triple covalent bond
 Hydrogen fluoride :: Polar covalent bond and
Iodine :: Single covalent bond
hydrogen bond
Sodium chloride :: Ionic bond
 Hydrogen chloride :: Polar covalent bond and
Magnesium chloride :: Ionic bond
hydrogen bond
Sodium fluoride :: Ionic bond
 Potassium bromide :: Ionic bond
28. Distinguish between: Ionic and Covalent bond; Ionic compounds and Covalent compounds.








Ionic bond
It is formed by the exchange of electrons between atoms of elements
It is formed between metallic and non-metallic
elements
e.g. NaCl, KI, etc



Covalent bond
It is formed by sharing of electrons in atom of
one or different elements
It is formed between atoms of only non-metallic
elements
e.g. H2, O2, etc
Ionic compounds
Covalent compounds
They have high melting points
 They have low melting points
Their densities are high
 Their densities are low
They are generally hard and solid in form
 They can be solid liquid or gaseous in state
They are generally soluble in water and
 They are generally soluble in organic solvents
insoluble in organic solvents
and insoluble in water
In molten or aqueous conditions they conduct
 They cannot conduct electricity
electricity
Answer the following in short:
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1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
GROUP TUITION
How many electrons are there in outermost orbit of
helium?
(A) 8
(B) 4
(C) 2 (D) 1
Which of the following elements is of inert group?
(A) Na
(B) Cl (C) Mg (D) Kr
How many electrons are there in chloride ion?
(A) 17
(B) 18 (C) 16 (D) 8
Which bond is present in NaCl crystal?
(A) Ionic
(B) Polar
(C) Covalent
(D) Hydrogen-bond
There are 13 electrons in an atom of an element. What
can be said about this element?
(A) It will form negative ion
(B) It will form positive ion
(C) It will form co-ordinate covalent bond
(D) Hydrogen bond
How many electrons are there in the outermost orbit
of inert gas elements?
(A) 8
(B) 2
(C) 8 or 2
(D) 0
How many electrons are shared by two atoms for the
formation of triple bond?
(A) 3
(B) 2
(C) 4 (D) 6
Which of the following possesses polar bond?
(A) H2O
(B) O2 (C) N2 (D) C12
How many electrons will be required by oxygen atom
to achieve electronic configuration like that of neon?
(A) 1
(B) 2 (C) 8
(D) 0
Which of the following bond shows formation of
oxygen molecule is correct?
(A) Ionic bond
(B) Covalent bond
(C) Double bond
(D) 
Which compound is formed when sodium reacts very
fast with water?
(A) Na2O
(B) NaOH
(C) NaCl
(D) Na2O2
In which solvent NaCl is soluble?
(A) Ether
(B) Carbon tetrachloride
(C) Benzene
(D) Water
The atom of which of the following forms dual closed
shell configuration by giving one electron?
(A) He
(B) H (C) Li (D) B
How are molecules and elements formed?
When two or more atoms of same or different element
combine together chemically, they form molecule or
compound.
Properties of molecules depend on what?
On electronic configuration of the atoms present in the
molecule and their way of bonding.
Why inert gases do not possess reactivity?
Atoms of inert elements contain eight electrons (2
electrons in helium) in their valence orbit and so they
have stable configuration. Hence they do not possess
reactivity.
What is meant by octet configuration?
Atoms of all inert gases except helium have eight
electrons in their valence orbit. This state of valence orbit
is called octet state.
Write rule of octet.
When the atoms of an element exchange or share their
valence electrons with one or more atoms, it results in the
configuration of octet and achieves an inert gas
configuration.
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19. Which type of elements possess tendency to form
positive ions?
Metallic elements.
20. Which type of elements possess tendency to form
negative ions?
Non – metallic elements
21. Give formula of aluminium chloride. Which element
in it loses electrons?
AlCl3, Aluminium loses electrons.
22. Mention only in the form of equation the formation of
chemical bond formed in magnesium chloride.
Mg  Mg2+ + 2e–
;
2Cl + 2e–  2Cl–.
 Mg2+ + 2Cl–  MgCl2.
23. How many chloride ions around each sodium ion and
how many sodium ions around each chloride ion are
arranged in a crystal of sodium chloride?
6 chloride ions are present around each sodium ion and 6
sodium ions around each chloride ion in a crystal
structure of common salt.
24. Which type of atoms do not form ionic bonds?
The atoms which neither gain nor lose electrons easily
from their valence orbit do not form ionic bonds.
25. What is doublet closed configuration? Which atom
occupies this structure?
When two atoms having only one orbit share electron to
get the stable structure like that of helium atom, give
doublet closed configuration. Hydrogen, lithium and
beryllium forms duplet closed configuration.
26. Explain only the electronic configuration of covalent
bond formation in the structure of chlorine molecule.
Electronic configuration of Cl is 2, 8, 7. It requires one
electron to obtain octet configuration. Thus two atoms of
Cl share 1 electron each and forms a single covalent bond.
27. What is called electron pair in chlorine molecule?
What is its function?
The electron pair in chlorine molecule is called bonding
electron pair. Its main function is to keep the Cl atoms
bonded together.
28. What is the valency of an atom?
The number of electrons an atom gains, loses or share to
form a bond with other element is called its valency.
29. Mention valency of chloride ion in barium chloride
and also valency of chloride in chlorine molecule.
The valency of chloride ion in barium chloride and
chlorine molecule both is –1.
30. How many covalent bonds are formed by how many
electrons in oxygen molecule?
In an oxygen molecule, two oxygen atoms form a double
covalent bond.
31. What is called polar Covalent bond?
Atoms of different electronegativity share the electrons to
form a covalent bond is called polar covalent bond.
32. In which compounds both types of bonds - ionic and
covalent bond are present?
Sodium hydroxide, sulphuric acid, ammonium nitrate,
potassium carbonate, etc contain both ionic and covalent
bonds.
33. Cotton clothes do not dry faster. Why?
As cotton clothes form hydrogen bond with water, the
water cannot evaporate easily and so cotton clothes do not
dry faster.
34. Molecules of water are not in free form. Why?
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IX science
AJAY PARMAR
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49.
GROUP TUITION
In any physical state of water, molecules of water are
always attracted by each other with a special attractive
force called hydrogen bond. Because of this Hbond
water molecules are never in free state
Give formula of magnesium chloride. Which element
in it loses electron?
MgCl2. Magnesium loses electron.
What is a substance made up of?
A substance is made up of elements, compound or
mixture.
How is a water molecule formed?
Two molecules of hydrogen and one molecule of oxygen
combine to form two molecules of water.
Give the names of elements of 8th group (inert group).
The elements of 8th group are helium(He), neon(),
argon(Ar), krypton(Kr), xenon(Xe) and radon(Rn).
Who proposed the octet rule?
Lewis proposed the octet rule.
What happens during the formation of molecules?
The energy of elements decreases and stability of
molecule increases during the formation of molecules.
State the main types of chemical bonds.
The main types of chemical bonds are ionic and covalent
bonds.
The electronic configuration of sodium ion is same as
which inert element?
The electronic configuration of sodium ion is same as
neon.
The electronic configuration of chloride ion is same as
which inert element?
The electronic configuration of chloride ion is same as
argon.
In which type of bonding the exchange of electrons
take place?
The exchange of electrons takes place in ionic bond.
The electronic configuration of magnesium ion is same
as which inert element?
The electronic configuration of magnesium ion is same as
neon.
The electronic configuration of oxide ion is same as
which inert element?
The electronic configuration of oxide ion is same as neon.
In which type of bonding does sharing of electrons
take place?
Sharing of electrons takes place in covalent bonds.
What is covalence of an atom?
In a molecule number of electrons in the atoms sharing
the covalent bond is called covalence of that atom.
State the number of pair of electrons shared in
hydrogen molecule, chlorine molecule, oxygen
molecule, nitrogen molecule and water molecule.
Hydrogen molecule and chlorine molecule  one pair of
electrons; oxygen molecule  two pairs of electrons,
nitrogen molecule  three pair of electrons and water
molecule  one pair of electron of oxygen with each of
the two hydrogen atoms.
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50. State the number of covalent bonds in hydrogen
molecule, chlorine molecule, oxygen molecule,
nitrogen molecule and water molecule.
Hydrogen molecule and chlorine molecule  single
covalent bond; oxygen molecule  double covalent bond,
nitrogen molecule  triple covalent bond and water
molecule  two single covalent bond (between oxygen
and two hydrogen atoms)
51. By what sign is the electrical charge formed on the
atoms of a compound containing polar covalent bond
represented?
The electrical charge formed on the atoms of a compound
containing polar covalent bond represented by .
52. Atom of which element has only one and stable orbit?
Helium has only one and stable orbit
53. What is required for an atom of an element to be
stable and inert?
A stable electronic configuration is required for an atom
of an element to be stable and inert.
54. How many electrons should be in the outermost orbit
of any atom of an element for the stability?
There should be eight electrons in the outermost orbit of
any atom of an element for stability. But if it has only one
electron orbit, there should be 2 electrons to achieve
stability.
55. Out of Ca, He, Ca2+and H which has a stable electron
configuration?
He and Ca2+ have a stable electron configuration.
56. Which ion will be formed from Al?
Positively charged Al+3 ion is formed from Al.
57. Write the electron configuration of sodium, chloride,
magnesium and oxide ion.
Electron configuration of sodium = 2, 8, 1; chloride = 2,
8, 7; magnesium= 2, 8, 2 and oxide ion = 2, 8.
58. Give the names of two ions which do not possess octet
in the outermost orbit still they are stable.
The outermost orbits of Li+ and Be2+ do not possess
complete octet and still they are stable.
59. What is a single covalent bond?
The bond formed by two atoms on sharing one electron
each of their outermost orbit, is known as single covalent
bond.
60. What is a double covalent bond?
The bond formed by two atoms on sharing two electrons
each of their outermost orbit, is known as double covalent
bond.
61. What is a triple covalent bond?
The bond formed by two atoms on sharing three electrons
each of their outermost orbit, is known as triple covalent
bond.
62. Mention the names of two covalent compounds, which
are soluble in water?
The covalent compounds which are soluble in water are
ammonia and alcohol.
63. Which is more stable ? An atom or an ion.
An ion is more stable.
64. Which type of bond is present in calcium chloride?
An ionic bond is formed in calcium chloride.
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