Lecture 2

Question 1

Steps to draw lewis structure

Answer 1

Step1- calculate the total no of valence e
Step2- put the atom written first in the middle

Question 2

Draw the lewis structure for CHBr3

Question 3

What are the 4 exceptions to the octet rule?

Answer 3

1) molecules with odd number of electrons e.g radicals
2) other natural radicals
3) molecules that an atom can hold less than octet (group 3) aluminium and boron
4) molecules that their orbital can hold more than octet (period3) phosphorus and silver

Question 4

Meaning of radical

Answer 4

Neutral species with unpaired electrons so odd number of electrons- very reactive
Radicals can be atoms or molecules

Question 5

Example of radicals

Answer 5

-NO
-Na(11e-odd)
-cl

Question 6

Resonance arrow meaning

Answer 6

Redistribution of electrons.
No bonds broken only electrons are rearranged

Question 7

What are the medical uses of nitrous oxide?

Answer 7

Nitrous oxide AKA laughing gas
Chemical formula: N20
Colourless non flammable gas
Used in dentistry, emergency department, surgery,

Question 8

Why is nitrous oxide called laughing gas?

Answer 8

Due to euphoric effects when inhaled, reduces anxiety and pain making patients feel calm and relaxed.

Question 9

How do you calculate formal charges?

Answer 9

Number of valence electrons minus number of electrons atom has in lewis structure

Question 10

Draw the 2 lewis structures of NO

Question 11

Draw the 2 lewis structures of oxygen.
Which is the structure we breath in? Why

Answer 11

We breath in radical structure (triplet state) as its radical so reacts with our Hb

Question 12

Explain the 2s+1 rule and use it to work out the states of different forms of oxygen lewis structures

Answer 12

Oxygen radical structure is triplet state

Question 13

Examples of less than octet exception

Answer 13

Group 3 aluminium and boron

Alcl3
Bcl3

Question 14

Examples of more than octet that dont obey octet rule

Answer 14

Period 3 and beyond
Have s,p and d orbitals

Pcl5
SF6