Chemical Changes and Structure

Question 1

What is Ionisation energy?

Answer 1

First ionisation energy is the energy required to remove 1 mole of electrons from 1 mole of gaseous atoms

2nd and subsequent ionisation energies are energies required to remove further moles of electrons.

Question 2

What happens to Covalent Radius when you move down a group?

Answer 2

The covalent radius increases as the number of occupied electron shells increases, which increases shielding.

Question 3

What happens to covalent radius when you move across a period?

Answer 3

The covalent radius decreases because of the increase in nuclear charge ( increase in atomic number ) attracts electrons more strongly.

Question 4

What happens to electronegativity when you move across a period?

Answer 4

Electronegativity increases

why? - there are more protons so nuclear charge is increased.

Question 5

Where are the strongest reducing agents on the electrochemical series?

Answer 5

The top right hand column.

Question 6

Where are the strongest oxidising agents on the electrochemical series?

Answer 6

The bottom left hand column

Question 7

What are oxidising agents used as?

Answer 7

They kill fungi and bacteria and break down coloured compounds.
so often used as bleach for clothe or hair (eg. hydrogen peroxide)

Question 8

What are examples of oxidising and reducing agents?

Answer 8

Oxidising Agents = Hydrogen peroxide, dichromate and permanganate ions are group ions that are strong oxidising agents in acidic solutions.

Reducing Agents = Carbon monoxide

Question 9

What are hydrogen bonds?

Answer 9

Hydrogen bonds are electrostatic forces of attraction between molecules that contain highly polar bonds.
they are the strongest intermolecular force.
hydrogen bonds exist between F-H, O-H, N-H

Question 10

What are permanent dipole-permanent dipole interactions?

Answer 10

Permanent dipole - permanent dipole interactions are additional electrostatic forces of attraction between polar covalent molecules.
pd-pd interactions are stronger than LDF’s for molecules with similar numbers of electrons.

Question 11

Describe Ionic bonding.

Answer 11

Ionic bonds are the electrostatic attractions between positive and negatives ions.
ionic compounds form lattice structures of oppositely charged ions

Question 12

How does difference in electronegativity affect bonding the of an atom?

Answer 12

No difference = Pure covalent bond
Small difference = Polar covalent bond
Large difference = Ionic bond

Question 13

What are London Dispersion Forces?

Answer 13

LDF’s are forces of attraction that operate between all atoms and molecules. they are the weakest type of intermolecular force.
they are formed as a result of electrostatic attraction between temporary dipoles and induces dipoles caused by movement of electrons in atoms and molecules

Question 14

What is the strength of London Dispersion Forces affected by?

Answer 14

The number of electrons within an atom or molecule

size of the molecule

Question 15

What is a pure covalent bond?

Answer 15

In a covalent bond, atoms share pairs of electrons. the covalent bond is a result of 2 positive nuclei being held together by their common attraction for the shared pair of electrons.

Question 16

What is covalent radius?

Answer 16

It is half the distance between the nuclei of 2 bonded atoms of the element.

It is a measure of the size of an atom.

Question 17

Do elements with low electronegativities tend to act as oxidising or reducing agents?

Answer 17

Reducing agents as they form ions by losing electrons.

Question 18

Describe the bonding of the first 20 elements.

Answer 18

Metallic = Li, Be, Na, Mg, Al, K, Ca
Pure covalent molecular = H2, N2, F2, O2, I2, Cl2, B2, S8, C60(fullerene)
Covalent Network = B, C (diamond/graphite), Si
Monatomic = Ar, He, Ne, Xe, Kr, Rn, Og

Question 19

Describe the solubility of polar and non polar substances in polar and non polar solutions.

Answer 19

Ionic compounds and polar compounds tend to be soluble in polar solvents (eg water) and insoluble in non polar solvents.
Non polar molecular substances tend to be soluble in non polar solvents and insoluble in polar solvents.

Question 20

What is a polar covalent bond?

Answer 20

Polar covalent bonds are formed when the attraction of the atoms for the pair of bonding electrons is different.
The polarity of a bond depends on the difference in electronegativity between atoms.

Question 21

What is a reducing agent?

Answer 21

A reducing agent is a substance which donates electrons.

Question 22

What is an oxidising agent?

Answer 22

An oxidising agent is a substance which accepts electrons.

Question 23

What is electronegativity?

Answer 23

Electronegativity is a measure of attraction an atom in a bond has for the electrons of the bond.

Question 24

What happens to electronegativity when you move down a group?

Answer 24

Electronegativity decreases.

why? - Atomic size increases (shells) so outer electrons are further from the positively charged nucleus.

Question 25

What happens to 1st ionisation energy across a period?

Answer 25

It increases.
Why?
>Nuclear charge increases - electrons held more tightly so are more difficult to remove
>Additional electron goes to 2nd shell - no difference to screening effect, increased nuclear charge pulls electrons and covalent radius decreases.
>Outer electron is closer to nucleus, more strongly held so 1st ionisation energy increases

Question 26

What happens to 1st ionisation energy moving down a group?

Answer 26

It decreases.
Why?
>Nuclear Charge increases making the outer electron harder to remove.
>Covalent radius increases, outer electron is further from the nucleus
>More inner electrons prevent outer electrons from nuclear charge, these inner electrons increasingly screen the outer electron from the nucleus. Consequently, the outer electron becomes easier to remove as the atom gets bigger, i.e. the first ionisation energy decreases on going down a group.

Question 27

What groups are the strongest oxidising and reducing agents in?

Answer 27

Strongest Oxidising = Group 1, Alkali Metals

Strongest Reducing = Group 7, Halogens