SECTION 3 - LEWIS THEORY

Question 1

Ionic bond

Answer 1

Electrons TRANSFERRED from 1 atom to another (non metal + metal)

Question 2

Covalent bond

Answer 2

Electrons SHARED from 1 atom to another (2 nonmetal)

Question 3

Lewis theory

Answer 3

Lewis stated that atoms combine to acquire electron configuration of noble gasses and valence electrons are shared/transferred

Question 4

Lewis symbol

Answer 4

Dots around symbol (representing valence electrons)

Question 5

Octet rule

Answer 5

When electrons are shared in a way that each atom acquires filled outershell of 8 valence electrons

Question 6

Duet rule

Answer 6

H fills 1s level with 2 electrons

Question 7

Single bond

Answer 7

2 bonding electrons

Question 8

Double bond

Answer 8

4 bonding electrons

Question 9

Nonpolar covalent bond

Answer 9

Electrons shared EQUALLY between atoms of bond (no separation of charge)

Question 10

Polar covalent bond

Answer 10

Electrons shared UNEQUALLY between atoms of bond (separation of charge)

Question 11

Electronegativity

Answer 11

Describes an atom’s ability to compete for electrons with another atom which its bonded (measure of pull of electron). Higher the electronegativity, the stronger

Question 12

Electronegativity trend periodic table

Answer 12

Increase across period left to right and increase up a group

Question 13

Dipole arrows

Answer 13

• Arrows go from S+ to S-
• The more electronegative one is S-

Question 14

Electronegativity trend

Answer 14

• Difference less than 0.4 = non polar covalent bond
• Difference between 0.4-2.0 = polar covalent bond
• Difference greater than 2.0 = ionic bond

Question 15

Opposite dipoles (CO2)

Answer 15

Cancel each other out. Bonds between C-O are polar, but since the arrows are opposite, they cancel out and the molecule is non polar

Question 16

Formal charge

Answer 16

Valence electrons - non bonding electrons - number of bonds.
- Formal charge has to be on the most electronegative atom in a resonance structure if there has to be a - charge, and + charge on least electronegative atom

Question 17

Non bonding electron

Answer 17

Valence electron -8(n)/2
- n is the number of atoms that is not central

Question 18

Reasonance structure

Answer 18

Occurs when you can draw 2 or more plausible lewis structures with equal correctness. The only thing that changes is the location of multiple bonds

Question 19

Reasonance bond rules

Answer 19

• Single bond between atom means 3 LP (6 electron on terminal)
• Double bonds between atom means 2 LP (4 electron on terminal)
• Triple bonds between atom means 1 LP (3 electron on terminal)
• Can only move electrons in P orbitals

Question 20

Exceptions on octet rules

Answer 20

1. Free radicals: Molecules with unpaired electrons
2. Incomplete octet: Some atoms (B, Al, Be) form 3 bones instead of 4 and are satisfied
3. Expanded valence shell: Elements in 3rd row and below CAN have more than an octet