Lecture 8 + 9 - Covalent Bonding

Question 1

Describe covalent bonding

Answer 1

electron pairs are shared between both participating atoms with the aim for both atoms to gain a stable structure

Question 2

what does a double covalent bond involve?

Answer 2

the sharing of two pairs of electrons

Question 3

what is a lewis structure?

Answer 3

method of describing covalent binding in polyatomic molecules - it shows valence electrons in dots and crosses

Question 4

what are the 6 factors favouring covalent bonding?

Answer 4

• High ionisation energies
• equal electron affinities
• equal/similar electronegativity
• high nuclear charge
• small atomic size
• number of valence electrons

Question 5

Describe bond polarity in non polar bonds

Answer 5

• between two atoms of equal/ similar electronegativity
• electrons are shared evenly between the two atoms
• no dipole is formed

Question 6

Describe bond polarity in polar bonds

Answer 6

• between atoms of different electronegativity
• separation of charge between one end and the other with greater electron density around the more electronegative atom
• bond has a dipole which affects the reactivity of the bond and the types of intramolecular forces

Question 7

Give 3 giant covalent structures

Answer 7

• graphite
• diamond
• silicon dioxide

Question 8

what is a dative covalent bond?

Answer 8

a covalent bond formed when both electrons are provided by one of the linked atoms

Question 9

what are the requirements for a dative covalent bond?

Answer 9

• the atom acting as the donor must have a lone pair of electrons
• the atom acting as the acceptor should have a vacant orbital to accept the electron pair being donated

Question 10

what are the 6 uses of dative covalent bonds in biology?

Answer 10

1. haemoglobin
2. myoglobin
3. cytochrome P450
4. vitamin B12
5. chlorophyll
6. photodynamic therapy

Question 11

Describe dative covalent bonds in medicine

Answer 11

function of some drugs depends on their ability to act as donation of electrons and acceptors for biological donors

Question 12

Give 4 examples of dative covalent bonds in medicine

Answer 12

1. D-penicillinamine -treatment of copper and arsenic poisoning
2. Dimercaprol - treatment of mercury, lead and arsenic poisoning
3. desferoxamine - treatment of iron overdose
4. Cis Platin - anticancer drug

Question 13

what is the number of bonds and bond angle for a linear molecule?

Answer 13

2 + 180

Question 14

what is the number of bonds and bond angle for a trigonal planar molecule?

Answer 14

3 + 120

Question 15

what is the number of bonds and bond angle for a tetrahedral molecule?

Answer 15

4 + 109.5

Question 16

what is the number of bonds and bond angle for a trigonal bipyramidal molecule?

Answer 16

5 + 90 + 120

Question 17

what is the number of bonds and bond angle for a octahedral molecule?

Answer 17

6 + 90

Question 18

what is the number of bonds and bond angle for a pyramidal molecule?

Answer 18

3 + 107

Question 19

what is the number of bonds and bond angle for a bent linear molecule?

Answer 19

2 + 104.5

Question 20

what is the number of bonds and bond angle for a square planar molecule?

Answer 20

4 + 90