EL

Question 1

Relative atomic mass

Answer 1

average mass of an atom of an element compared to 1/12 the mass of a C-12 atom.

Question 2

Relative isotopic mass

Answer 2

mass of an atom of an isotope compared to 1/12 the mass of a C-12 atom.

Question 3

Relative formula mass/ relative molecular mass

Answer 3

average mass of a molecule or formula unit compared to 1/12 of C-12.

Question 4

Avogadro’s constant

Answer 4

6.02 x 10^23, the number of particles in 12 g of C-12.

Ar can be worked out using mass spec.

Question 5

shape of s and p orbitals

Answer 5

spherical, dumbbell

Question 6

How many electrons can occupy a single orbital?

Answer 6

2

Question 7

Equation linking energy and frequency

Answer 7

Energy (J) = Planck’s constant (…) x frequency (Hz)

Question 8

How are elements in the periodic table ordered?

Answer 8

in order of atomic/ proton number

Question 9

How are elements in the same group of the periodic table similar?

Answer 9

have the same number of electrons in their outer shell so similar chemical properties.

Question 10

Similarities between absorption and emission spectra

Answer 10

• Both line spectra
• Lines at same positions for a given element
• Lines become closer together at higher frequencies
• Lines represent electronic transitions to or from a particular energy level.

Question 11

Differences between absorption and emission spectra

Answer 11

• Absorption: black lines on a coloured background

- Emission - coloured lines on a black background.

Question 12

How do absorption spectra arise?

Answer 12

Electrons in their ground state can absorb energy at discrete frequencies and transition to a higher energy level - an excited state. The frequencies of radiation absorbed correspond to the differences between energy levels as E=hv. These frequencies are missing on an absorption spectrum - they are shown as black lines.

Question 13

How do emission spectra arise?

Answer 13

Electrons can release energy by dropping from a higher to a lower energy level. Energy is released at specific frequencies because energy levels are quantised and is shown as coloured lines on a black background on an emission spectrum.

Question 14

First ionisation enthalpy definition

Answer 14

the amount of energy required to remove 1 electron from each atom in 1 mole of gaseous atoms, to form 1 mole of gaseous 1+ ions.

Question 15

First ionisation enthalpy general equation

Answer 15

X(g) ⇒ X+(g) + e-

Question 16

what 3 factors does first ionisation enthalpy depend on?

Answer 16

Atomic radius, nuclear charge and electron shielding

Question 17

Describe and explain the trends in first ionisation enthalpy across a period.

Answer 17

Across a period, IE increases because electrons in the same shell, which are the same distance from the nucleus and experience the same shielding and more strongly attracted to the nucleus by the greater number of protons present. More energy is required to remove an electron

Question 18

Describe and explain the trends in first ionisation enthalpy down a group.

Answer 18

Down a group, first IE decreases as there is less attraction between the nucleus and outer e-. This is because outer e- are further from the nucleus and experience more shielding.

Question 19

Describe and explain the relative reactivities of s block and p block metals in terms of ionisation enthalpies.

Answer 19

S- block metals are more reactive than p- block metals in the same period because they have a lower nuclear charge so valence electrons are less strongly attracted so IEs are lower and outer electrons are lost more readily than from p- block metals.

Question 20

Reaction of a group 2 metal and oxygen

Answer 20

2M + O2 ⇒ 2MO

A metal oxide is produced.

Question 21

Reaction of a group 2 metal and water

Answer 21

M + 2H2O ⇒ M(OH)2 + H2

A metal hydroxide and hydrogen gas are produced.

Question 22

How and why are the first ionisation enthalpies of groups 2 and 3 elements different?

Answer 22

This is why first ionisation enthalpies for period 3 elements are lower than for the period 2 element in the same group.

Question 23

How does the reactivity of group 2 metals and water/ oxygen change down the group and why?

Answer 23

Reactivity increases down the group because the outer electrons are further from the nucleus, so are less strongly attracted and are more readily lost.

Question 24

Why are group 2 oxides and hydroxides basic?

do not need to give reactions

Answer 24

Oxides react with water to form the metal hydroxide.

Metal hydroxides dissolve in water and dissociate to form OH- ions, so making to solution alkaline.

Question 25

Reactions of group 2 metal oxides and hydroxides with water

Answer 25

MO + H2O ⇒ M2+ + 2OH-

M(OH)2 ⇒ M2+ + 2OH-

Question 26

Equations for the reaction of a group 2 oxide or hydroxide with hydrochloric acid

Answer 26

MO + 2HCl ⇒ MCl2 + H2O

M(OH)2 + 2HCl ⇒ MCl2 + 2 H2O

Question 27

Solubility trend of group 2 hydroxide

Answer 27

increases down the group

Mg(OH)2 is insoluble.

Question 28

Solubility trend of group 2 carbonate

Answer 28

decreases down the group.

Question 29

Thermal stability of group 2 carbonate - trend down the group

Answer 29

increases down the group - higher temperature is required for decomposition to occur.

Question 30

Why does thermal stability of a group 2 carbonate increase down the group?

Answer 30

Smaller ions with the same charge (e.g. Mg2+) have a higher charge density, so are able to distort the large carbonate ion to a greater extent. The compound decomposes at a lower temperature.