Chapter 9 (part one): Chemical Bonding I: Lewis Theory

Question 1

Define Lewis theory

Answer 1

A simple model of chemical bonding using diagrams the represent bonds between atoms as lines or pairs of dots. In this theory, atoms bond together to obtain octets (eight valance electrons)

Question 2

Define Lewis structure (Lewis dot structures)

Answer 2

A drawing that represents bonds between atoms as shared or transferred electrons; the valence electrons of atoms are represented as dots

Question 3

Chemical bonds occur because…?

Answer 3

They lower the potential energy between the charged particles that compose atoms

Question 4

Which law states that when atoms approach each other, the electrons of one atom are attracted to the nucleus of the other and vice versa

Answer 4

Coulumbs law

Question 5

What are the three main types of bonding?

Answer 5

Ionic bonding
Covalent bonding
Metallic bonding

Question 6

When a metal bonds with a non metal what occurs?

Answer 6

One or more electrons is transferred from the metal to the nonmetal

(Because metals have low ionizations energies and non metals have high electron affinities)

Question 7

Oppositely charged ions _____ one another, ____ their overall potential energy as described by Coulomb’s law. The resulting bond is called…?

Answer 7

Attract
Lowering
An Ionic bond

Question 8

Because nonmetals have _____ ionization energies, when a nonmetal bonds with a nonmetal neither atom transfers electrons instead they ______ electrons

Answer 8

High

Share

Question 9

Nonmetals share electrons, the shared electrons interact with the nuclei of both of the bonding atoms, lowering their potential energy in accordance with _____ ______. The resulting bond is a _______ bond

Answer 9

Coulomb’s law

Covalent

Question 10

The most stable arrangement for a covalent bond is the one with the ______ potential energy

Answer 10

Lowest

Question 11

Define bonding theories

Answer 11

Models that predict how atoms bond together to form molecules

Question 12

Metals have ____ ionization energies and so when metallic bonding occurs the ____ ____ model is used and it shows…?

Answer 12

Low
Electron sea
That all of the atoms in a metal lattic pool their valance electrons. These pooled electrons aren’t localized to a single atoms but are delocalized over the entire metal. The positively charged metal atoms are then attracted to the sea of electrons, holding the metal together

Question 13

Define chemical bond

Answer 13

The sharing or transfer of electrons to attain stable electron configurations for the bonding atoms

Question 14

If electrons are transferred, as between a metal and a nonmetal, the bond is _____

Answer 14

Ionic

Question 15

If the electrons are shared, as occurs between two nonmetals, the bond is _____

Answer 15

Covalent

Question 16

Define octet rule

Answer 16

The tendency for most bonded atoms to possess or share eight electrons in their outer shell to obtain stable electron configurations and lower their potential energy

Question 17

Define lattice energy

Answer 17

The energy associated with forming a crystalline lattice from gaseous ions

Question 18

The formation of an ionic compound is exothermic, why?

Answer 18

Because when the positively and negatively charged ions come together the potential energy decreases and the energy is emitted as heat

Question 19

Define Born-Haber cycle

Answer 19

A hypothetical series of steps based on Hess’s law that represents the formation of an ionic compound from its constituent elements

Question 20

As the ionic radii ______ as we move down the column, the ions cannot get as close to each other and therefore ____ release as much energy when the lattice forms

Answer 20

Increases

Don’t

Question 21

Lattice energies become _____ exothermic (_____ negative) with increasing ionic radius

Answer 21

Less

Less

Question 22

Lattice energies become _____ exothermic (_____ negative) with increasing magnitude of ionic charge

Answer 22

More

More

Question 23

Define bonding pair

Answer 23

A pair of electrons shared between two atoms

Question 24

Define lone pair

Answer 24

A pair of electrons associated with only one atom

Question 25

Define nonbonding electrons

Answer 25

Lone pair electrons (A pair of electrons associated with only one atom)

Question 26

Name the 4 steps for drawing a Lewis structure

Answer 26

1. Find the total number electrons that will be used (# of valence electrons)
2. Create a skeletal structure by putting a bond between each set of bonding atoms
3. Put the remaining electrons around the atoms
4. Make sure all the non hydrogen atoms have a full octet. If not, adjust accordingly

Question 27

Molecular compounds have _____ bonds within the molecules but _____ intermolecular forces between molecules. This results in molecular bonds having _____ melting points and boiling points than ionic compounds

Answer 27

Strong
Weak
Lower

Question 28

What do you do to show the structures are resonance structures

Answer 28

Put a double headed arrow between the two diagrams

Question 29

Define resonance structures

Answer 29

Two or more valid Lewis structures that are shown with double-headed arrows between them to indicate that the actual structure of the molecules is intermediate between them

Question 30

Define resonance hybrid

Answer 30

The actual structure of a molecule that is intermediate between two or more resonance structures

Question 31

Which structure is the structure that actually exists? Resonance structure or resonance hybrid structure?

Answer 31

Resonance hybrid structure

Question 32

Define formal charge

Answer 32

The charge that an atom In a Lewis structure would have if all the bonding electrons were shared equally between the bonded atoms

Question 33

What is the formal charge equal to?

Answer 33

of valence electrons - (# of nonbonding electrons + 1/2 # of bonding electrons)

Question 34

The sum of the formal charges in molecules or ions must equal…?

Answer 34

The overall charge of the ion or molecule

Question 35

What are two guidelines to follow in terms of formal charge when drawing Lewis structures?

Answer 35

1. smaller formal charges on individual atoms are better than larger ones
2. when formal charges cannot be avoided, negative formal charges reside on the most electronegative atom

Question 36

Main group elements in the third row of the periodic table and beyond often exhibit ______ which means…?

Answer 36

Hypercoordination
They are bonded to more than four other atoms or appear to have more than 4 pairs of electrons (an octet) around the central atom

Question 37

Hypercoordinate compounds are said to have _____ _____ because it looks like their are more than eight electrons around the central atom in the Lewis structure

Answer 37

Expanded octet

Question 38

define ionic bond

Answer 38

a chemical bond formed between two oppositely charge ions, generally a metallic cation and a nonmetalic anion, that are attracted to one another byt electrostatic forces

Question 39

define covalent bond

Answer 39

a chemical bond in which two atoms two atoms share electrons that interact with both nuclei , lowering the potential energy of each atom through electrostatic interactions

Question 40

define octect

Answer 40

eight electrons in a valence shell of an atom

Question 41

why are bond energies always positive?

Answer 41

because it takes energy to break a bond