Chemical Bonding

Lecture 7.1

Electrons Continued…

₃Li 1s² 2s¹

₁₁Na 1s² 2s² 2p⁶ 3s¹

₁₉K 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹

Valence Electrons = electrons in the outermost energy level

- depicted using Lewis Dot Structures

Lewis Dot Structures = diagram that shows an atoms valence electrons

1) Chemical symbol surrounded by its valence electrons

Ex: Li Na K

2) 2 electrons per side (top, bottom, left, right)

Ex: Mg B C N

O F Ne

Octet Rule = atoms tend to combine in such a way that they each have eight electrons in their valence shells

Na

Octet Rule = atoms tend to combine in such a way that they each have eight electrons in their valence shells

F

Chemical Bond = a link between atoms in molecules or ions, represented by an imaginary line drawn from the nucleus of 1 atom to the nucleus of the other

- the systems is always striving for

Bond Length =

Ex: H₂

- attractive forces (+/-) offset repulsive forces (+/+ and -/-)

Ionic Bond = force that results from the electrostatic attractions of oppositely charged ions

- transfer of electrons!

- think ionization energy and electron affinity

Cl

Na

Ex:

- low ionization energy

- high electron affinity

Ex: NaCl

Na

Cl

1 valence electron

7 valence electrons

Na⁺¹

Cl^-1

Cation

Gave away 1 electron

Anion

Gained 1 electron

+

−

Attraction!!

The attraction between positive and negative is the IONIC BOND!!

Ionic Bonding

- form

- Strength of ionic bond depends directly

q⁺ • q^-

F_attraction = k

d²

Covalent Bond =

- attempting to achieve stable octet (or duet for H!)

Ex: F₂

F

F

F

F

+

=

Ex: O₂

O

O

+

=

O

O

N

N

+

=

N

N

Ex: N₂

Covalent Bonding

- multiple bonds increase electron density between nuclei which:

1)

2)