1: Fundamental Chemistry

Question 1

What is an isotope?

Answer 1

An atom with a different number of neutrons.

(As normally atoms would have same number of protons & neutrons)

Question 2

How is atomic weight (Ar) calculated?

Answer 2

Number of protons + number of neutrons

Question 3

What is the difference between ionic and covalent bonds?
What type of bonds are these?

Answer 3

Ionic = bonds between positive and negative ions
Covalent = sharing of electrons between atoms
(Both intramolecular bonds)

Question 4

What are the properties of ionic compounds?

Answer 4

• High melting and boiling points (due to being very strong bonds)
  e.g. Hydroxyapatite is found in bones and teeth - is a key component based on ionic bonds
• Soluble in water

Question 5

What are the properties of covalent compounds?

Answer 5

Lower melting and boiling points, e.g. H20 and CH4

Question 6

What are co-ordinate (dative) bonds?

Answer 6

A type of covalent bond (also intramolecular) between two atoms, but both of the shared electrons come from one of the bonding partners

Question 7

Define ‘electronegativity’

Answer 7

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Fluorine is the most electronegative element (4.0 on the Pauling scale)

Question 8

How does electronegativity relate to polarity?

Answer 8

If there is a big difference in electronegativity between 2 atoms in a bond then the bond is polar

Question 9

Name the 3 main types of intermolecular bonds

Answer 9

1. van der Waals
2. Dipole-dipole
3. Hydrogen bonds

Question 10

What are van Der Waals bonds / interactions?

Answer 10

Weak intermolecular forces that are quick and occur when electrons by chance accumulate at one side of both atoms, causing an instantaneous slight negative charge.

Question 11

What are dipole-dipole interactions?

Answer 11

Electrostatic forces between molecules with permanent dipoles, where the positive end of one molecule is attracted to the negative end of another. (As electrons are pulled towards the more electronegative atom)
- Slightly stronger than van Der Waals

Question 12

What is hydrogen bonding?

Answer 12

A weak electrostatic attraction between polar molecules which occurs when a hydrogen atom binds to a lone pair of electrons on a highly electronegative atom.

Question 13

How do you calculate number of moles?

Answer 13

Mass (in grams) / formula weight

Question 14

How do you work out molar concentration?

Answer 14

Number of moles = concentration x volume