Topic 3: Bonding

Question 1

When are chemical compounds formed? What process is this? How does potential energy have a role in this?

Answer 1

Formed atoms are bonded together, which is an EXOTHERMIC process
-since it’s exothermic, it releases energy, meaning that compounds have LESS potential energy than the individual atoms they are formed from

Question 2

Ionic compounds: properties

Answer 2

Metal and nonmetal
1. electrons transferred (from valance shell)
2. high melting and boiling points
3. form crystals*
4. conduct electricity in solution and as a liquid
5. dissolve in water (dissociation) (soluble)

Question 3

Covalent/molecular compounds: properties

Answer 3

nonmetal and nonmetal
1. share electrons
2. lower melting and boiling points
3. do not conduct electricity
4. insoluble in water

Question 4

Chemical bonds are formed when valence electrons are …

Answer 4

IONIC: transferred from one atom to another
COVALENT: shared between atoms
METALLIC: mobile in a free moving “SEA OF ELECTRONS”

Question 5

What is a “sea of electrons”?

Answer 5

in metallic bonds, electrons are mobile in a free moving sea of electrons

Question 6

Polar vs non-polar molecules

Answer 6

polar: asymmetrical, must have polar bonds
non-polar: symmetrical and/or have NO polar bonds

Question 7

What happens when an atom gains an electron?

Answer 7

-becomes a negative ion
-its radius increases

Question 8

What happens when an atom loses an electron?

Answer 8

-becomes a positive ion
-its radius decreases

Question 9

Stable electron configuration

Answer 9

-gained by bonding with other atoms
-stable when they have a full valance level

Question 10

Most atoms need how many electrons to fill their valance level? Which elements are the exception? How are the noble gasses different?

Answer 10

1. Most atoms need 8 electrons to fill valance shell
2. Hydrogen (H) and helium (He) need only 2 electrons to fill valance shell
3. Noble gasses (GROUP 18) have filled valance shells, usually don’t bond with other atoms

Question 11

What are lewis structures?

Answer 11

Electron-dot diagrams which represent the valance electron arrangement in elements, compounds and ions

Question 12

Orbitals

Answer 12

1 “s” orbital- first two electrons
3 “p” orbitals- remaining, each p must have 1 electron before next p gains a second
3d-5

Question 13

Electronegativity

Answer 13

indicates how strongly an atom of an element attracts electrons in a chemical bond

Question 14

Electronegativity difference ranges (regarding polarity)

Answer 14

0.0-0.4= non-polar covalent
0.4-1.7= polar covalent
1.7+= ionic

Question 15

Ionic compounds with polyatomic ions have which types of bonds?

Answer 15

BOTH covalent and ionic bonds

Question 16

Intermolecular forces of attraction (IFAs)

Answer 16

-allow different particles to be attracted to each other to form solids and liquids
-the stronger the IFA, the harder to break the bond

Question 17

Hydrogen bonds

Answer 17

(not a bond)
-strong IFA
-exists between Hydrogen and Fluorine, Oxygen, Nitrogen (Hold the FONe)
-tend to have much higher melting and boiling points bc of strong IFA

Question 18

What are the physical properties of a substance and how can they be explained?

Answer 18

can be explained in terms of IFA and chemical bonds. properties include:
1. malleability
2. conductivity
3. solubility
4. ductility (ability to be stretched, pulled, etc. without breaking)
5. hardness
6. melting and boiling point