Bonding test feedback

Question 1

What is meant by the term covalent bond?

Answer 1

The nuclear attraction between the nucleus of multiple atoms and the shared pair of electrons.

Question 2

What is meant by the term ionic bond?

Answer 2

The electrostatic forces of attraction between positively and negatively charged ions in a giant lattice.

Question 3

What is a permanent dipole and how is it formed?

Answer 3

Formed when two atoms in a covalent bond have a difference in electronegativity, causing electrons to be pulled closer to the more electronegative atom (an unequal sharing of electrons). This creates a partial negative charge on one atom and a partial positive charge on the other, resulting in a polar bond.

Question 4

Explain why a molecule of Hydrogen chloride is polar.

Answer 4

Because chlorine is more electronegative than hydrogen. This causes the shared electrons in the covalent bond to be pulled closer to the chlorine atom, giving it a partial negative charge and leaving the hydrogen atom with a partial positive charge.

Question 5

In terms of electron pairs, explain why the bond angles in NH4+ are all 109.5º

Answer 5

• 4 total electron pairs
• 4 bonding pairs
• 0 lone pairs
• so bond angles are all 109.5º
• as the electron pairs are arranged as far apart from each other as possible.

Question 6

Explain why the shape of NH3 is not the same as the shape of BF3

Answer 6

As NF3 has
- 4 total electron pairs
- 1 lone pair
- 3 bonding pairs
so is trigonal pyramid and 107º

whereas,

BF3 has
- 3 bonding pairs
- 3 total electron pairs
- 0 lone pairs
so is trigonal planar and 120º

Question 7

Explain why shape X has no overall polarity.

Answer 7

• dipoles cancel each other out
• arranged symmetrically around central atom
• so overall non-polar

Question 8

Explain why X has a greater b.p. than Y.

Answer 8

mention:
- number of electrons
- van der Waals
- other intermolecular forces e.g. hydrogen
- so more heat energy required to overcome.