Intermolecular Forces

Question 1

What is the Valence Shell Electron Pair Repulsion Theory (VSEPR)

Answer 1

• Where negatively charged electron pairs electrostatically repel other electron pairs
• Therefore electron pairs are spread out as far apart as possible (So they don’t repel)
• Lone pairs of electrons repel other electron pairs to greater extents, forming unique shapes

Question 2

How can you figure out shape of molecule from formula

Answer 2

1) Identify central atom

2) Identify n(Valence electrons in central atom)

3) Identify n(Bonding electrons of central atom)

4) Identify n(Lone electron pairs of central atom)

Question 3

What does the shape of a molecule depend on

Answer 3

n(Atoms in molecule)

n(Bonds from central atom)

n(Unbonded pairs of electrons around central atom)

Question 4

What are the different shapes of molecules

Answer 4

Trigonal Planar

Tetrahedral

V-Shaped (Bent)

Pyramidal

Linear (2 Atoms)

Linear (3 Atoms)

Question 5

What is trigonal planar

Answer 5

3 atoms around central atom

No unbonded pairs of electrons

Approx 120* between every outer atom

Question 6

What is tetrahedral

Answer 6

4 atoms around central atom

No unbonded pairs of electrons

Approx 109.5* between every outer atom

Question 7

What is pyramidal

Answer 7

3 atoms around central atom

1 unbonded pair of electrons

Approx 109* between every outer atom

Question 8

What is v-shaped (bent)

Answer 8

2 atoms around central atom

Either 1 or 2 unbonded pairs around central atom

Question 9

What is linear (2 atoms)

Answer 9

Diatomic molecules

Linear molecule, regardless of unbonded pairs

Question 10

What is linear (3 atoms)

Answer 10

Three atoms in molecule

No unbonded pairs around central atom

Approx 180* between every outer atom