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

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Flashcards in Chapter 9 (part one): Chemical Bonding I: Lewis Theory Deck (41):
1

Define Lewis theory

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)

2

Define Lewis structure (Lewis dot structures)

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

3

Chemical bonds occur because...?

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

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

Coulumbs law

5

What are the three main types of bonding?

Ionic bonding
Covalent bonding
Metallic bonding

6

When a metal bonds with a non metal what occurs?

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)

7

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

Attract
Lowering
An Ionic bond

8

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

High
Share

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

Coulomb's law
Covalent

10

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

Lowest

11

Define bonding theories

Models that predict how atoms bond together to form molecules

12

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

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

13

Define chemical bond

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

14

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

Ionic

15

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

Covalent

16

Define octet rule

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

17

Define lattice energy

The energy associated with forming a crystalline lattice from gaseous ions

18

The formation of an ionic compound is exothermic, why?

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

19

Define Born-Haber cycle

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

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

Increases
Don't

21

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

Less
Less

22

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

More
More

23

Define bonding pair

A pair of electrons shared between two atoms

24

Define lone pair

A pair of electrons associated with only one atom

25

Define nonbonding electrons

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

26

Name the 4 steps for drawing a Lewis structure

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

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

Strong
Weak
Lower

28

What do you do to show the structures are resonance structures

Put a double headed arrow between the two diagrams

29

Define resonance structures

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

30

Define resonance hybrid

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

31

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

Resonance hybrid structure

32

Define formal charge

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

33

What is the formal charge equal to?

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

34

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

The overall charge of the ion or molecule

35

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

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

36

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

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

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

Expanded octet

38

define ionic bond

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

39

define covalent bond

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

40

define octect

eight electrons in a valence shell of an atom

41

why are bond energies always positive?

because it takes energy to break a bond