Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Unit 7a:
Molecules
1.
Student Name: _____________Key___________________
Class Period: ________
Website upload 2014
Page 1 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Page intentionally blank
Website upload 2014
Page 2 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Unit 7a Vocabulary:
1. Binary compound: A compound that consists of only two elements.
2. Dipole attractions: The attraction of the partially negative (δ-) end of
one polar molecule to the partially positive (δ+) end of another polar
molecule.
3. Dipole moment: An arrow along the line of symmetry in a polar
molecule that shows the net direction that electrons are being pulled
towards the partially negative (δ-) end of the molecule.
4. Electronegativity difference: The difference in electronegativity
between two elements in a bond.
5. Electrical conductivity (of metals): The ability of a substance to allow
electrons to pass from atom to atom through the substance from a
source of electricity to an electrical ground.
6. Electrolyte: A solution containing dissolved ions that can conduct
electricity within the solution.
7. Empirical formula: The simplest whole-number mole ratio of
elements in a compound; used to write the formulas of ionic
compounds.
8. Formula mass: The sum of the atomic masses of an element or
compound, measured in grams per mole (g/mole). Reported to the
nearest tenth (0.1) of a g/mole.
9. Hydrogen bonds: The strong attraction of the H (δ+) end of one polar
molecule to the N, O, or F (δ-) ends of another molecule. The two
molecular ends form temporary covalent bonds.
10. InterMolecular Attractive Force (IMAF): The forces that hold
molecules together in the solid and liquid phases. These are the
forces that must be overcome to melt or boil a substance. IMAF
forces are also called “van der Waal’s forces”.
11. Ionic compound: Compounds consisting of a metal and a nonmetal
ionic bonded in a whole-number ratio.
12. London Dispersion Force: The weak attractive forced caused by
temporary dipoles in nonpolar molecules.
Website upload 2014
Page 3 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
13. Metallic bond: A bond formed between metal atoms as they
collectively share their conducting electrons evenly between metal
kernals.
14. Molecular formula: The actual number of nonmetal atoms in a
molecule; a whole-number multiple of the empirical formula.
15. Molecule: A group of nonmetal atoms covalently bonded together to
form a distinct particle.
16. Network solid: A crystal lattice formed from covalently bonded
nonmetal atoms with no distinct molecules.
17. Nonpolar molecule: A molecule with symmetrical electron
distribution resulting in any polar bonds cancelling each other out to
yield no partially charged ends.
18. Percent composition: The formula mass of an element divided by the
formula mass of the compound containing the element and the
divisor then multiplied by 100.
19. Polar molecule: A molecule with asymmetric electron distribution
resulting in partially charged ends.
20. Polyatomic ion: An ion formed by atoms bonding together in way
that a net charge (positive or negative) is formed.
21. Ternary compound: A compound that consists of three (or more)
elements, usually containing a polyatomic ion.
Website upload 2014
Page 4 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Notes page:
Website upload 2014
Page 5 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Unit 7a Homework Assignments:
Assignment:
Website upload 2014
Date:
Page 6 of 43
Due:
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Types of Compounds
Objective: How do substance properties depend on composition?
Compound: A compound is a substance formed by the chemical bonding
of atoms. The type of compound is determined by the type of bonding
involved.
Website upload 2014
Page 7 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Ionic Compounds
Objective: How do substances form compounds swapping electrons?
Ionic Compounds:
 Ionic Compounds are formed by ionic bonding.
 Ionic compounds are found in crystal form of alternating + and charged ions.
 As a full + and full - charges are involved, ionic attractions are strong.
 Ionic bonds tend to have high melting and/or boiling points; ionic
bonds tend not to evaporate.
 When dissolved in water or melted, the ions separate and allow
conduction of electricity. The solution formed is called an
electrolyte.
 An attraction between ions is named ionic attraction.
 Melting or dissolving ionic compounds breaks the ionic bond. When
the bonds have already been broken the ionic reactions are very fast.
Website upload 2014
Page 8 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Molecular Compounds
Objective: How do substances form compounds sharing electrons?
Molecular Compounds:
 Molecular compounds are formed by covalent bonding, either polar
or nonpolar.
 Covalent bonding forms individual particles called molecules which
can attract each other to form the solid or liquid phase.
 Molecules may have oppositely charged ends, which allow them to
attract one another. These are called InterMolecular Attractive
Forces (IMAF), and are weaker than ionic attractions.
 Molecular compounds are more easily melted and boiled, so their
solid melting and boiling points are low compared to solid ionic
compounds. Molecular compounds also tend to evaporate more
quickly, and their solids are softer than ionic or metallic bonds.
 Note that dissolving in water or melting does NOT break the covalent
bond. No ions are formed, so molecules do NOT normally conduct
electricity.
Website upload 2014
Page 9 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Network Solids
Objective: What substances are made in continually bonded crystals?
Network Solids:
 Network solids (Atomic solids) are covalently bonded solids (usually
nonpolar) that do not form separate molecules.
 Network solids are one single crystal made of nonmetal atoms
connected with a continuous network of covalent bonds with no
areas of weakness that may break apart. Network solids are among
the hardest substances known, such as diamond, corundum, and
quartz.
 Network solids are nonconductors of electricity and poor heat
conductors.
Watch Bozeman Science Covalent Network Solids video
https://www.youtube.com/watch?v=PU9rzTjLyb4
Website upload 2014
Page 10 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Allotropes
Objective: What elements may be found in different forms?
Allotropes:
 Allotropes are different forms of the same element.
 Different bonding arrangements between atoms result in different
structures with different chemical and physical properties.
 Allotropes occur only with certain elements, in Groups 13 through 16
in the Periodic Table.
 Elements that form allotropes are: B, C, N, O, Al, Si, P, S, Ga, Ge,
As, Se, In, Sn, Sb, Te, Tl, Pb, Bi, and Po.
 Carbon forms the most allotropes of any element.
o Carbon may be found naturally as both diamond and graphite.
Note that these are on both ends of the Moh’s hardness scale for
minerals. Carbon may also be found in a “ball-like” structure,
known as a fullerene, as carbon-60 (C60).
Diamond
Website upload 2014
Graphite
Page 11 of 43
C 60 Fullerene
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Metallic Compounds
Objective: What special properties do metallic compounds have?
Metallic Compounds:
 Metallic compounds do not technically form compounds with other
metal atoms.
 Metal atoms share electrons by losing them. Metals ‘swap’ valence
electrons freely.
 Metal atoms have positively charged kernals located amidst many
free-moving electrons. These free-moving electrons are evenly
distributed and easily move, allowing metals to conduct electricity in
all phases.
Website upload 2014
Page 12 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Bonding Energies
Topic:
Objective: How does bonding affect the energy of compounds?
Bonding Energies:
 Chemical Compounds are formed when atoms are bonded together.
Energy is absorbed when a bond is broken; energy is released when
a bond is formed.
i. Individual atoms are unstable and have higher energies.
o When atoms combine into compounds, energy is released
(exothermic), and the compound is more stable than the
original atoms.
ii. Compounds have a lower potential energy than their individual
atoms.
o Breaking a chemical bond requires energy (endothermic), and
the energy required is now a part of the more unstable atoms.
o The more bonds (electron pairs) between atoms, the more
energy per electron pair, and the shorter the bond length.
Website upload 2014
Page 13 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Types of Compounds
Objective: How the different compounds compare and/or contrast?
Physical Properties of Types of Compounds:
Ionic, Covalent, and Metallic Bonds - YouTube
https://www.youtube.com/watch?v=CGA8sRwqIFg
Website upload 2014
Page 14 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Molecular Polarity
Objective: How may you tell if a molecule is polar or nonpolar?
Molecular Polarity:
 Molecular polarity is different than the polarity of the bonds within
the molecule.
 A bond is polar if the electronegative difference (END) between
bonding atoms is 0.5 or higher. A molecule may have polar bonds
and still be a nonpolar molecule. The polarity of the molecule is
determined by the polarity and positioning of all bonds within a
molecule.
 Determining the polarity of a molecule may tell you several things:
i. How high (or low) the melting and/or boiling points of the
substance;
ii. How easily the liquid phase of the substance evaporates (vapor
pressure);
iii. Whether the substance will dissolve in water or another solvent.
 Molecular polarity causes intermolecular attractive forces, and is
the reason certain adhesives bind, and why some animals can climb
walls and glass. The IMAF act like Velcro; you can attach and
detach the molecules without damaging them, and some molecules
are stronger than others, just as some Velcro is stronger.
Website upload 2014
Page 15 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Notes page:
Website upload 2014
Page 16 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Molecular Shape
Objective: How will the shape determine molecular properties?
Molecular shape determines the properties of the molecule.
Website upload 2014
Page 17 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Molecular Polarity
Objective: How
will thePolarity:
shape determine molecular Polarity?
Determining
Molecular
Polar Molecules:
 Polar molecules contain nonmetal atoms that share electrons
unequally when forming molecules. If the resulting molecule is
asymmetrical (unbalanced), there is a greater concentration of
electrons on one side of the molecule compared to the other side of
the molecule.
 The molecule will have one side charged partially negative and the
other side charged partially positive. The oppositely charged ends of
these molecules are “poles”, making the entire molecule polar. Polar
molecules may attract each other, (δ+) end of one polar molecule to
the (δ-) of the other molecule. These are the IMAF as mentioned
earlier.
 If the molecule has polar bonds in an asymmetrical arrangement, the
molecule as a whole will have a net polarity towards the more
electronegative atom in the molecule. The net direction of electron
pull towards the more electronegative atom may be diagrammed by
determining the sole axis of symmetry and drawing an arrow (dipole
moment) towards the more electronegative atom.
 The diagrams on the next page show some polarity examples.
Examples of each molecule used are found at the end of your packet.
Website upload 2014
Page 18 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
POLAR MOLECULES: A Polar Molecule has one line of symmetry. The line of
symmetry forms the Dipole Moment. Look up the electronegativity (EN) of the atoms at
either end of the line of symmetry. The more EN end will be δ- and the less EN end will
be δ+. The line of symmetry has an arrowhead placed on the more EN end, forming the
Dipole Moment, or the direction (moment) in which the electrons are pulled towards.
Polar molecules have asymmetric electron distributions.
Structural
Formula
Website upload 2014
Lines of symmetry:
either side of the line
is a mirror image.
Write the EN of the
atoms on either end of
the line of symmetry.
Page 19 of 43
Draw an arrowhead on the
end of the line with the
highest EN. This is the
Dipole Moment. The end
with the higher EN has a
greater pull on the electrons,
so it is δ- charged. The other
end is δ+ charged, forming a
complete polar molecule.
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Molecular Polarity
Objective: How will the shape determine molecular Polarity?
Nonpolar Molecules:
 If the molecule has a symmetrical shape, then the electrons are
distributed evenly throughout the molecule, and the entire molecule is
nonpolar, even IF it contains polar bonds.
 Nonpolar molecules have equal pull of electrons on all sides of the
molecule, so no dipole moment forms. Since the molecule lacks
oppositely charged ends, and attractive forces will be extremely
weak.
 Small nonpolar molecules are usually found in the gaseous state at
room temperature, with examples including methane (CH4), propane
(C3H8), and butane (C4H10). Larger nonpolar molecules may be
liquids at room temperature, with examples including octane (C8H18)
and benzene (C6H6). Large nonpolar molecules are normally in the
solid phase at room temperature, such as p-dichlorobenzene
(C6H4Cl2), which is what mothballs are made of.
Website upload 2014
Page 20 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 21 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
NONPOLAR MOLECULES:
 Nonpolar molecules have two or more lines of symmetry. The
electronegativity differences along these lines of symmetry are equal,
so there is an equal pull on electrons from all sides of the molecule.
 The molecule has a symmetrical electron distribution.
Watch Crash Course Science Polar and Nonpolar molecules video (Have seen already; a repeat!)
https://www.youtube.com/watch?v=PVL24HAesnc
Website upload 2014
Page 22 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
London Dispersion Force
Objective: What attraction holds nonpolar molecules together?
London Dispersion Force:
 London Dispersion Force attractions are formed in nonpolar
molecules. As there are no permanently charged positive or negative
ends, these attractions are very weak. The attractions are a
combination of temporary poles due to electron movement around
the molecule in smaller molecules.
 London dispersion forces generally get stronger as the size of the
molecule increases.
Watch Bozeman Science London Dispersion Force video
https://www.youtube.com/watch?v=1iYKajMsYPY
Website upload 2014
Page 23 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Dipole Attraction
Objective: What attraction holds polar molecules together?
Dipole Attraction:
 Dipole Attractions are formed in polar molecules.
 Dipole attractions are simply the attraction of the oppositely charged
ends of two molecules. The partially positive end of one molecule
attracts toward the partially negative end of another molecule. This
attraction allows these substances to exist as solids and liquids at
higher temperatures than are possible for nonpolar molecules of
equivalent size.
Website upload 2014
Page 24 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Hydrogen Bonds
Objective: What attraction holds polar molecules (water) together?
Hydrogen Bonds:
 Hydrogen Bonds are formed in some polar molecules.
 Water is one of the most notable molecules with this special type of
attractive force. In water, the hydrogen atom from the partially
positive end of one water molecule is attracted to the oxygen atom
from the partially negative end of another water molecule. There is
still an electronegative attraction, as the END between H and O is 1.3
and therefore strongly polar. There are more attractive forces
occurring with these temporary covalent hydrogen bonds between one
water molecule’s oxygen and one of the hydrogen atoms in another
molecule of water. The oxygen is so electronegative (and is of such
small radius) that the oxygen atom moves the electron it shares with
its own hydrogen, and the now the hydrogen is ‘free’ to bond with
oxygen in another water molecule.
 Note that the primary bond between a water molecule’s oxygen and
its own hydrogen atoms is MUCH stronger than the hydrogen bond
between different molecules oxygen and hydrogen atoms. Still the
hydrogen bonding between water molecules is responsible for the
amazing properties of water.
Website upload 2014
Page 25 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Water Properties due to Hydrogen Bonding:
i. Water has an extremely high melting point, boiling point, heat of
fusion, and heat of vaporization for a molecule of that size;
ii. Water has the ability to form a ‘skin’ at the surface known as surface
tension that forms a meniscus and allows small animals to walk on
water;
iii. Water has the ability to climb narrow spaces, known as “capillary
action”, due to the adhesion between the wall spaces and water
molecules;
iv. Water molecules may be deflected by an electronic field.
 Hydrogen atoms may form hydrogen bonds with other nonmetal
atoms with a high electronegativity and a small atomic radius, such
as nitrogen (EN of 3.0) and fluorine (EN of 4.0).
 Chlorine (EN of 3.2) does NOT form hydrogen bonds, as chlorine
has a third PEL and its size interferes with the temporary covalent
hydrogen bond forming.
Watch Bozeman Science Dipole and Hydrogen Bonds video
https://www.youtube.com/watch?v=cERb1d6J4-M
Website upload 2014
Page 26 of 43
Unit 7a: Molecules-key
Topic:
Regents Chemistry ’14-‘15
Mr. Murdoch
Hydrogen Bonds
Objective: What attraction holds polar molecules (water) together?
Website upload 2014
Page 27 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Topic: Molecular Attractive Forces
Objective: How do different molecular attractive forces compare?
Attractive Force: Type, Strength, and resulting Molecular Properties.
Melting &
Boiling
points
Vapor
Pressure
(Evaporation
potential)
Molecule
Polarity
Type of Attractive Force
Strength of
Attractive
Force
0 or 1
Polar
(If H end of one molecule is
attracted to a N, O, or F end of
another molecule) =
HYDROGEN BOND
Strong
High
Low
0 or 1
Polar
(Any OTHER polar molecule) =
DIPOLE
Moderate
Moderate
Fair
2 or more
Nonpolar
LONDON DISPERSION
FORCE
Weak
Low
High
Lines of
Symmetry
What can you do with this information?
Using the flowchart on page 26, you should be able to:
i. Identify whether a compound is molecular, ionic, or a network solid
based on its properties;
ii. Draw dot diagrams of simple molecules;
iii. Draw structural formulas of simple molecules;
iv. Determine the shape of simple molecules;
v. Determine if simple molecules are polar or nonpolar;
vi. Draw the dipole movement and identify the partially charged ends of
polar molecules;
vii. Determine the type of attractive force between simple molecules.
Website upload 2014
Page 28 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Attractive Force Summary: Flowchart
Website upload 2014
Page 29 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Notes page:
Website upload 2014
Page 30 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Student name: _________________________
Class Period: _______
Please carefully remove this page from your packet to hand in.
Types of Compounds homework
Circle the correct answer in each multiple choice question below.
1. Which of the following substances is molecular?
a) NaCl
c) K2O
b) CO2
d) C
2. Explain why one of the wrong choices is not molecular. Choice: _a, c, or d_
Why? NaCl & K2O are ionic (metal & nonmetal); C is an element
3. Which of the following substances has a very high melting point and will
conduct electricity when in the liquid phase?
b) CO2
c) CH4
d) SiO2
a) NaCl
4. Explain why one of the wrong choices is not correct. Choice: _b, c, or d_
Why? CO2 & CH4 are covalent nonmetal molecules; SiO2 is covalent metalloid
and nonmetal molecule
For each of the molecules represented by the structural formulas on the next page
indicate:
i. If the molecule is polar or nonpolar;
 If you find the molecule is nonpolar, skip to step iii.
ii. If the molecule is polar, draw the dipole moment and mark which end is
partially positive and which side is partially negative;
iii. Identify the shape of the molecule;
iv. Identify the type of attractive force that will hold molecules of this substance
together in the liquid and solid phase.
Cont’d next page
Website upload 2014
Page 31 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 32 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Notes page:
Website upload 2014
Page 33 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
H ̶ Cl
Website upload 2014
Page 34 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 35 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
H ̶ O
ǀ
H
Website upload 2014
Page 36 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 37 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
H ̶ N ̶ H
ǀ
H
Website upload 2014
Page 38 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 39 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
H ̶ S
ǀ
H
Website upload 2014
Page 40 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 41 of 43
Unit 7a: Molecules-key
Regents Chemistry ’14-‘15
Mr. Murdoch
Cl
ǀ
Cl ̶ C ̶ Cl
ǀ
H
Website upload 2014
Page 42 of 43
Unit 7a: Molecules-key
Website upload 2014
Regents Chemistry ’14-‘15
Mr. Murdoch
Page 43 of 43