Topic 1: Atomic structure and the Periodic Table

Question 1

Define Relative Atomic Mass

Answer 1

weighted mean of the atoms of a normal sample relative to the 1/12th the mass of the c-12 isotope.

Question 2

Define Relative Isotopic Mass

Answer 2

mass of an isotope of the element relative to 1/12th the mass of the C-12 isotope

Question 3

Define Relative Molecular Mass

Answer 3

mass of a molecule relative to 1/12th the mass of the C-12 isotope

Question 4

Main processes involved in mass spectrometry

Answer 4

1) The sample is vaporised
2) The sample is ionised
3) the ions are accelerated by an electric field
4) the accelerated ions pass through a magnetic field and are deflected
5) the ions are detected and recorded

Question 5

Define First Ionisation Energy

Answer 5

The energy required to remove one electron from each atom in one mole of gaseous atoms producing one mole of gaseous ions with one positive charge.

Question 6

General Trend for First Ionisation energies

Answer 6

going across a period, ionisation energy increases.

going down groups, ionisation energy decreases.

Question 7

Define Second Ionisation energy

Answer 7

The energy required to remove one electron from each ion in one mole of gaseous ions with a single positive charge producing one mole of gaseous ions with two positive charges.

Question 8

Electronic Configuration of Copper

Answer 8

1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^1, 3d^10

Question 9

Electronic configuration of Chromium

Answer 9

1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^1, 3d^5

Question 10

Evidence for electron shells and subshells

Answer 10

successive ionisation energies provide evidence for the existence of electron shells.
first ionisation energies provide evidence for the existence of electron subshells.

Question 11

Relative Atomic Mass Equation

Answer 11

(mass x abundance) / 100

Question 12

The table below gives information on the heights of peaks in a mass spectrum of chromium.
M/z	Height of peak in cm
50 	0.4
52	8.0
53	0.9
54	0.2

A) Calculate the percentage abundance of each isotope to one decimal place
B) Calculate the relative atomic mass of chromium to 2 dp.

Answer 12

a) 0.4+8+0.9+0.2=9.5
abundances: 4.2, 84.2, 9.5, 2.1

b) answer= 52.05

Question 13

Explain why successive ionisation energies increase

Answer 13

.After each ionisation the positive charge on the ion increases
.So to remove the next electron, more energy is required to overcome this greater attraction

Question 14

There is a general increase in first ionisation energy from Na to Ar. Explain this trend

Answer 14

.Same electron shell
.Same distance from nucleus
.Nuclear charge increases so attraction to the nucleus from the outer electron increases

Question 15

Explain why in group 1 of the periodic table, the first ionisation energy decreases down the group.

Answer 15

Atoms become larger
electrons further away from the nucleus
more shielding electrons

Question 16

Define Orbital

Answer 16

the region in an atom which can hold up to 2 electrons with opposite spins

Question 17

The diagram below shows the visible line spectrum of hydrogen

a) What quantity is representing along the horizontal axis
b) Is this quantity increasing or decreasing from left to right
c) Explain why the atomic spectrum consists of a series of lines
d) To which energy level do the transitions corresponding to the visible lines in the spectrum of hydrogen relate

Answer 17

a) energy
b) decreasing
c) an excited electron drops back down from various higher energy shells to a lower energy shell
d) electrons dropping down to shell 2

Question 18

Explain why the second ionisation energy of each element is higher than the corresponding first ionisation energy

Answer 18

electron removed
positive charge
increased attraction
more energy required

Question 19

Why do the maxima of the second ionisation energies occur at sodium and potassium

Answer 19

Sodium and potassium have one electron in the outer shell
to remove a second electron requires breaking in to a full inner shell
more energy required to break into inner shell

Question 20

explain why the first ionisation energy of magnesium is greater than that of aluminium

Answer 20

Although nuclear charge of Al is greater
last electron added to Al goes into 3p subshell
extra shielding
more energy needed

Question 21

explain why the melting temperatures increase from sodium to aluminium

Answer 21

positive charge on the metal ion increases
greater charge density
number of electrons in the delocalised electron region increases
attraction between ions and the delocalised electrons increases
more energy required

Question 22

write an equation to represent the first ionisation energy of O.

Answer 22

O(g) -> O⁺(g) + e⁻

Question 23

define the term periodic as applied to elements of the periodic table

Answer 23

patterns in properties

repeat across different periods