Covalent Bonding

Question 1

Covalent Bonding

Answer 1

The sharing of electron pairs to achieve stability between nonmetals to form a molecule (group of non-metallic atoms held together by covalent bonds). Non-metallic atos tend to have high electronegativities, therefore they attract electrons easily.

Question 2

Octet Rule

Answer 2

Outer shells have the ability to hold more electrons, the octect can be expanded as the maximum capacity has not been reached.

Question 3

Answer 3

Question 4

Answer 4

Question 5

VSEPR Theory

Answer 5

VSEPR theory predicts the shape of molecules.
A molecule will assume the shape that minimises electron pair repulsions.
Electron pairs around the central atom will be as far apart as possible.

Question 6

Non-polar covalent bonds

Answer 6

Covalent bonds in which the bonding electron pair is shared equally and is uniformly distributed between the nuclei of two bonded atoms are called non-polar covalent bonds.

Question 7

Polarity

Answer 7

Question 8

Polar Covalent bonds

Answer 8

Covalent bonds are unsymetrically distributed as electrons are not shared equally, occurs between atoms of different electronegativities. However, polar covalent bonds are not purely covalent, it has some characteristics of ionic bonding, although the transfer of electrons is not fully complete. However, if electronegativity difference is two great, or greater than 1.8, an ionic bond forms.

Question 9

Determining non-polar and polar molecules

Answer 9

Molecules containing only non-polar bonds are non-polar molecules. All polar molecules contain polar bonds, however some molecules with all polar bonds may be considered non polar, as the arrangement of the molecule cancels out the charge.

Question 10

Answer 10

Question 11

Properties of covalent molecular substances

Answer 11

• have low melting and boiling points due to weak intermolecular forces
• are usually liquid or gaseous at room temperature due to weak intermolecular forces
• do not conduct electricity because the molecules are electrically neutral
• are soluble in water if polar, and soluble in non-polar solvents if non-polar (the ‘like-dissolves-like’ rule)
• are soft.

Question 12

Answer 12

Question 13

Name and Explain the shape of sulfur dioxide

Answer 13

SO2 is trigonal planar bent in shape. Sulfur is the central atom in an SO2 molecule, it has 3 pairs of electrons surrounding it. Around the sulfur atom there are 2 bonding pairs and 1 nonbonding pair of electrons. According to the VSEPR theory, electron pairs will organise around the central atom to maximise distance and minimse repulsion. Hence in So2, the 3 pairs of electrons take up a bent trigonal planar arrangement around the sulfur atom. However, only two corners of the trigonal planar are occupied by atoms, the molecule is bent.