5.3- Covalent Bonding

Question 1

Define covalent bonding

Answer 1

The strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 2

How is a covalent bond formed?

Answer 2

When electrons are shared between elements that have a high electronegativity

Question 3

Why is a covalent bond strong?

Answer 3

• the shared pair of electrons is an area of high electron density found between the two atoms
• there are strong electrostatic forces of attraction between the shared pair of negatively charged electrons and both positively charged nuclei of the bonding atoms involved
• these require a lot of energy to overcome

Question 4

What is a double bond?

Answer 4

2 shared pairs of electrons Eg. O2

Question 5

What is a triple bond?

Answer 5

3 shared pairs of electrons Eg. N2

Question 6

What structures have covalent bonding?

Answer 6

• molecules- methane and water
• macromolecules- diamond and graphite

Question 7

What is a dative covalent bond?

Answer 7

• Covalent bond formed when both electrons are donated by the same atom
• once formed it acts in the same way as a regular bond

Question 8

Explain fully the coordinate bonding in 2 molecules

Answer 8

Ammonium ion :

• the nitrogen atom is bonded to 3 hydrogen atoms
• means that it has one lone pair of electrons and 3 bonding pairs
• lone pair bonds with an electron deficient hydrogen ion to form a coordinate bond
• this coordinate bond is represented by an arrow pointing to the electron deficient atom

Aluminium chloride:

• aluminium forms 3 bonding pairs with 3 chlorine molecules as it is in group 3
• it cannot form any more covalent bonds as it is electron deficient
• between the two AlCl3 molecules a coordinate bond forms between the Cl atom one molecule and the electron deficient Al on the other
• thus between the two molecules, two coordinate bonds are formed

Question 9

What are lone pairs?

Answer 9

Unbounded electron pairs on the central atom

Question 10

What is average bond enthalpy?

Answer 10

Measure of average energy needed to break the bond

Question 11

Why do simple molecular structures have low melting and boiling point?

Answer 11

Small amount of energy is enough to overcome the intermolecular forces

Question 12

Simple molecular structures dissolve in what type of solvents?

Answer 12

Non polar solvents

Question 13

List some properties of giant covalent structures

Answer 13

• High melting and boiling point
• non conductors of electricity except graphite
• insoluble in polar and non polar solvents

Question 14

Define metallic bonding

Answer 14

Electrostatic attraction between the positive metal ion and the sea of delocalised electrons

Question 15

What is the shape and bond angle in a shape with 2 bonded pairs and 0 one pairs?

Answer 15

Linear - 180°

Question 16

What is the shape and bond angle in a shape with 3 bonding pairs and 0 lone pairs?

Answer 16

Trigonal planar - 120°

Question 17

What is the shape and bond angle in a shape with 4 bonded pairs?

Answer 17

Tetrahedral- 109.5°

Question 18

What is the shape and bond angle In a shape with 6 bonded pairs?

Answer 18

Octahedral - 90°

Question 19

What is the shape and bond angle in a shape with 3 bonded pairs and 1 lone pairs?

Answer 19

Pyramidal - 107°

Question 20

What is the shape and bond angle in a shape with 2 bonded pairs and 2 lone pairs?

Answer 20

Non linear - 104.5°

Question 21

By how many degrees does each lone pair reduce the bond angle?

Answer 21

2.5°