File No.29/03/05/11/2014
IX CLASS - IIT/N.T.S.E FOUNDATION - OLYMPIAD
ANDHRA PRADESH - TELANGANA
2014-2015 PROGRAM M E
1ST- PERIODIC CLASSIFICATION - SOLUTION
1.
The atomic weights of “Be” and “In” were corrected by Mendeleef using the formula
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Atomic weight=Equivalent weight x valency
2.
Modern periodic table is based on the atomic number of the elements. The experiment which proved the
significance of the atomic number was Mullikan’s oil drop experiment.
3.
The statement that is not true for the long form of the periodic table it reflects trends in physical and
chemical propertiesof the elements it helps to predict the relative ionicity of the bond between any two
elements.
4.
The atomicity of a noble gas is 1.
5.
If the differentiating electron enters (n-1)d-sublevel. The element is A transition element.
6.
Atoms with three of their outer most orbits incompletely filled with electrons are present in Lanthanides.
7.
Sulphur and Chlorine is not an anamalous pair.
8.
In the long form of periodic table all non-metals are placed in p - block.
9.
For alkali metals the electronic configuration in the water most sheel is (n-1)s2p6,ns1,ns1.
10.
The electronic configuration of d-block elements is (n-1)d1-10ns1-2 .
11.
When a neutral atom is converted to the anion its Size increases.
12.
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K  ,Cl ,Ca2 , Sc3 all these ions contain Electrons in the valence sheel.
13.
The low electron affinity value of nitrogen is due to Half-filled 2p sublevel.
14.
Electronegativity is the property related to Bonded atoms in a molecule.
15.
Atom becomes ion by Either oxidation or reduction.
16.
Generally Alkali metals have lowest ionization energy. So, electronic configuration corresponds to an
element having lowest ionization energy 1s22s22p63s1.
17.
The electron affinity of bromine atom is equal to the Ionisation potential of bromide ion
18.
The electronegativities of two elements A and B are 2.1 and 1.8. Then the type of bond formed between
them is Polar covalent bond.
19.
Beryllium resembles Aluminium in properties. This is mainly due toEqual electro negativity values of elements.
20.
Diagonal relationship is shown by Elements of second period.
1.
The Similarity in outer electronic configuration for the periodicity in the properties of elements.
2.
Al3+ has low ionic radius than Mg2+ because Al3+ has high nuclear charge than Mg2+.
3.
Na+, Mg2+, Al3+, and Si4+ are isoelectronic ions. Their ionic size Na+> Mg2+> Al3+> Si4+.
CHALLENGER
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File No.29/03/05/11/2014
IX CLASS - IIT/N.T.S.E FOUNDATION - OLYMPIAD
4.
Lanthanoid contraction is caused due to the imperfect shielding on outer electrons by 4 f -electrons from
the nuclear charge.
5.
The ionization energy of nitrogen is more than that of oxygen because of the extra stability of half-filled p
orbitals in nitrogen.
6.
The ionisation potential of “X+” ion is equal to the electron affinity of “ X2+ ” ion.
7.
Elements X, Y and Z have atomic numbers 19, 37 and 55 respectively. ‘Y’ would have an ionization potential
between those of X and Z statements.
8.
Given A [He] 2s1, B [Ne]3s1 , C [Ar] 4s1 order is correct for the first ionization potentials is A>B>C.
9.
Halogens generally have heighest electron offinity value 1s2 2s2 2p5.
10.
Electronegativity of Lithium is approximately equal to Mg.
11.
d is a given transition series the elements differ generally in the number of electrons
12.
13.
The correct order of ionization energies is Cs  Rb  Na .
Regarding electron affinity, the wrong statement is the E.A. of “Ne” is more than that of “F”.
14.
The best oxidizing agent among the following is Fluorine.
15.
Among O, C, F, Cl and Br, the increasing order of atomic radii is F < O < C < Cl < Br.
16.
Pauling’s scale of electronegativity for elements are useful in predicting Polarity of molecules.
17.
An element has nine positive charges in its nucleus its common oxidation state is –1.
18.
If the seventh period is completed, the atomic number of the last element would be 118.
19.
Stable electronic configuration of a transition metal 1s2 2s2 2p6 3s2 3p6 4s2 3d5.
20.
An atom of element has 2K, 8L and 3M electrons. Then that element is placed in III A group.
BRAIN TWISTERS
1.
d-block elements show variable oxidation states and these elements form alloys.
2.
Atomic radius is effected by effective nuclear charge, number of orbits and shielding effect.
3.
Atomic sizes of 4d and 5d transition elements become almost equal, due to which their properties are very
close, Zr and Hf resemble very closely, the crystal structure and other properties of lanthanides are very
similar are correct for consequences of Lanthanide contraction.
4.
Greater is the nuclear charge, greater is the electron gain enthalpy, Nitrogen has zero electron gain enthalpy.
Electron gain enthalpy decreases from chlorine to iodine in the group Chlorine has highest electron gain
enthalpy are correct.
5.
As we more from left to right, Non-metallic character, Size of atoms and Ionisation energy increase.
6.
a) Shortest period
-
H to He
b) Short period
-
Li to Ne
c) Long period
-
Rb to Xe
d) Longest period
-
Cs to Rn
1) Ionization energy 
-
Nuclear charge and Stable electronic configuration
2) Units of ionization energy
-
e.V/atom or K.cal/mole
3) Ionization energy decreases
-
On moving down the group
4) Ionization energy increases
-
On moving left to right in a period
a) Highest electronegativity value
-
F
b) Least electronegative element
-
Cs
-
Effective nuclear charge
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7.
8.
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c) Electronegativity
CHALLENGER
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2
3) Site of the atom
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d) Electronegativity
9.
10.
1

IX CLASS - IIT/N.T.S.E FOUNDATION - OLYMPIAD
-
Site of the atom
a) Carbon
-
2.5
b) Nitrogen
-
3.0
c) Aluminium
-
1.6
d) Cesium
-
0.8
Atomic number is equal to either the number of electrons (or) number of protons in an atom.
Both Assertion and Reason are corect and reason doesnot explain assertion.
11.
The number of elements in 2nd and 3rd period are equal similarly number of elements in 4th and 5th period
are equal.
Both Assertion and Reason are correct and Reason doenot explain Assertion
12.
Generally p-block elements are non metals and form ionic as well as covalent compounds.
Both are correct and Reason doesnot explain Assertion.
13.
Half of internuclear distance between the adjacent atoms of a solid metallic crystal is called crystal radius.
The effect of increase in the number of orbits in an atom increases the atomic size.
Both are correct but reason does not explained assertions.
14.
Second ionization enthalpy will be higher than the first ionization enthalpy.
Ionisation enthalpy is a quantitative measure of the tendency of an element to lose an electron.
Both are correct and reason doenot explain assertion.
15.
Lanthanide contraction is due to Less effective sheilding by 4f-orbitals
16.
The decreasing order of the size is Hydride ion, hydrogen atom, proton.
18.
Fe, Co, Ni, Cu all belongs to same period so, they have nearly same atomic radii.
19.
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2015
Number of groups present in the periodic
table-are
18.
20.
1A° = 10 -8cm.
1.
Chalcogens, Halogens, Pnicogens are p-block elements.
Alkaline earth metals are s-block elements.
2.
Atomic numbers15 is Phosphorus belongs to pnicogens and 35 atomic number is Bromine belongs to
halogen families.
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Both pnicogens and halogens are p-block elements.
3.
Helium atomic number 2 configuration 1S2 actually it is s-block but placed is zero group elements which is
p-block.
4.
Given E atomic number is 14 i.e, it is silicon 1S2 2P2 2P6 3S2 3P2 . So, ‘E’ belongs to 3rd period and maximum
number of elements present in 3rd period are Na, Mg, al, si, P, S, cl, Ar (8).
5.
The term periodicity in the properties of elements states, Reoccur after certain regular interval elements are
arranged in the increasing order of their atomic numbers similar elements .
6.
Anion > atom > cation  radius of atom > Cation > Anion
7.
Li atomic number 3 and
I atomic number 53
CHALLENGER
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IX CLASS - IIT/N.T.S.E FOUNDATION - OLYMPIAD
So, this LiI compound the ratio of anion size to cation size has the maximum value. In, LiI, the anion is
largest and cation is smallest.
8.
O, S, Se, Te belongs to oxygen family VI group elements.
O - Atomic number 8
S - Atomic number 16
Se - Atomic number 34
Te - Atomic number 52
as As we move from top to bottom in a group Atomic vadii increases.
9.
As the atomic number increases with in a group, the atomic size increases accordingly.Among the isoelectronic
ions lesser the nuclear charge, larger is the size.
10.
In isoelectronic ions, lesser the nuclear charge, larger is the size.
SO, S2- is larger in size
11.
The reaction, Mg  g  Mg2  g   2e  occurs in two steps:
IE1
Mg  g  
 Mg  g   e  ;  H 178kcal mol1
IE2
Mg  g  
 Mg2  g  e  ;  H 348kcalmol1
Mg  g   Mg2  g   2e  ;  H 526kcalmol1
12.
One mole of magnesium in the vapour state absorbed 1200 kJ of energy. If the first and second ionization
enthalpies of magnesium are 750 and 1450 kJ mol–1 respectively, the final composition of the mixture is
69% Mg+, 31% Mg2+
13.
IE of phosphorus is greater than Si and S due to its half filled stable configuration. First ionization enthalpies
of Si, P, S and Cl are 786, 1012, 999, 1256 kJ mol–1 respectively. Now follow the order of the elements and
write their values accordingly.
14.
There is an abnormal jump in the 7th ionization enthalpy, therefore, the element has 6 valence electrons and
hence it belongs to group 16. Nevertheless, there is a big jump in the 5th ionization enthalpy. This should no
be confused with the inert gas configuration but is rather due to the reason that after the removal of four
electrons from the p-sub-shell, the 5th electron has to be removed from a ns-orbital.
15.
Number of moles of Li 
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7
 103
1000  7
Number of moles of Na 
23
 103
1000  23
Both valency is are equal so, energy required to convert atoms to their respective cations is nothing but
Ionisation enthalpy.
Electron affinities of B, C, N and O are in B < C < O > N.
17.
The electron affinity is Se < O < S.
18.
The decreasing order of basic nature in the following oxides is Na2O, MgO, Al2O3, CuO.
19.
Zn forms amphoteric oxide.
20.
In each period, the strongest oxidising behaviour is for halogen.
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16.
CHALLENGER
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