Topic 1

Question 1

What are the three sub-atomic particles?

Answer 1

Proton, Neutron, Electron

Question 2

What is the atomic number (Z)?

Answer 2

The atomic number (Z) is the number of protons in the nucleus.

Question 3

What is the mass number (A)?

Answer 3

The mass number (A) is the total number of protons and neutrons in the atom.

Question 4

What is relative isotopic mass?

Answer 4

Relative isotopic mass is the mass of one atom of an isotope compared to one twelfth of the mass of one atom of carbon-12.

Question 5

What are isotopes?

Answer 5

Isotopes are atoms with the same number of protons but different numbers of neutrons.

Question 6

Why do isotopes have similar chemical properties?

Answer 6

Isotopes have similar chemical properties because they have the same electronic structure.

Question 7

What is relative atomic mass?

Answer 7

Relative atomic mass is the average mass of one atom compared to one twelfth of the mass of one atom of carbon-12.

Question 8

What is relative molecular mass?

Answer 8

Relative molecular mass is the average mass of a molecule compared to one twelfth of the mass of one atom of carbon-12.

Question 9

What does a mass spectrometer do?

Answer 9

A mass spectrometer can determine all the isotopes present in a sample of an element and identify elements.

Question 10

What does m/z stand for?

Answer 10

m/z stands for mass/charge ratio.

Question 11

How is the relative atomic mass on the periodic table calculated?

Answer 11

The relative atomic mass quoted on the periodic table is a weighted average of all the isotopes.

Question 12

What is the significance of the charge and mass number in a mass spectrum?

Answer 12

If asked to give the species for a peak in a mass spectrum, then give charge and mass number, e.g., 24Mg*.

Question 13

What is the formula for Relative Atomic Mass (R.A.M)?

Answer 13

R.A.M = E (isotopic mass x % abundance)

Question 14

How is R.A.M calculated for Magnesium (Mg)?

Answer 14

R.A.M = (78.7 x 24) + (10.13 x 25) + (11.17 x 26) / 100 = 24.3

Question 15

What is the formula for R.A.M using relative abundance?

Answer 15

R.A.M = (isotopic mass x relative abundance)

Question 16

What are the isotopes of Chlorine (Cl) and their relative abundances?

Answer 16

Cl has two isotopes: Cl-35 (75%) and Cl-37 (25%)

Question 17

What are the isotopes of Bromine (Br) and their relative abundances?

Answer 17

Br has two isotopes: Br-79 (50%) and Br-81 (50%)

Question 18

What is the significance of the peak with the largest m/z in mass spectrometry?

Answer 18

It represents the complete molecule and is called the parent ion or molecular ion.

Question 19

What happens to a molecule in a mass spectrometer?

Answer 19

It often breaks up and gives a series of peaks caused by the fragments.

Question 20

What is the m/z of a 24Mg2+ ion?

Answer 20

The m/z would be 12.

Question 21

What are some uses of mass spectrometers?

Answer 21

1. Radioactive dating to determine age of fossils or human remains.
2. Quality control in the pharmaceutical industry.
3. Drug testing in sports.

Question 22

How are mass spectrometers used in planetary exploration?

Answer 22

They help identify elements on other planets, which may have different compositions of isotopes.

Question 23

What is first ionisation energy?

Answer 23

The energy required when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge.

Question 24

What is second ionisation energy?

Answer 24

The energy required when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge.

Question 25

What are the factors that affect ionisation energy?

Answer 25

1. The attraction of the nucleus (more protons = greater attraction)
2. The distance of the electrons from the nucleus
3. Shielding of the attraction of the nucleus.

Question 26

Why are successive ionisation energies always larger?

Answer 26

When the first electron is removed, a positive ion is formed, increasing the attraction on the remaining electrons, thus requiring more energy to remove the next electron.

Question 27

How are ionisation energies linked to electronic structure?

Answer 27

The patterns in successive ionisation energies for an element provide important information about the electronic structure of that element.

Question 28

What does a big jump in ionisation energy indicate?

Answer 28

A big jump between successive ionisation energies indicates that an electron is being removed from a shell closer to the nucleus with less shielding.

Question 29

What does the equation for first ionisation energy follow?

Answer 29

The equation always follows the same pattern, regardless of whether the atom normally forms a +1 ion or is gaseous.

Question 30

What does a large difference in ionisation energies suggest about an element’s group?

Answer 30

A large difference suggests the element is in group 2 of the periodic table, as the third electron is removed from an inner shell closer to the nucleus with less shielding.

Question 31

Why has helium the largest first ionisation energy?

Answer 31

Helium has its first electron in the first shell closest to the nucleus and has no shielding effects from inner shells. It has a bigger first ionisation energy than hydrogen as it has one more proton.

Question 32

Why do first ionisation energies decrease down a group?

Answer 32

As one goes down a group, the outer electrons are found in shells further from the nucleus and are more shielded, so the attraction of the nucleus becomes smaller.

Question 33

Why is there a small drop from Mg to Al?

Answer 33

Al is starting to fill a 3p subshell, whereas Mg has its outer electrons in the 3s subshell. The electrons in the 3p subshell are slightly easier to remove because they are higher in energy and are also slightly shielded by the 3s electrons.

Question 34

Why is there a general increase in first ionisation energy across a period?

Answer 34

As one goes across a period, the number of protons increases, making the effective attraction of the nucleus greater. The electrons are being added to the same shell which has the same shielding effect, and the electrons are pulled in closer to the nucleus.

Question 35

Why has Na a much lower first ionisation energy than Neon?

Answer 35

Na has its outer electron in a 3s shell further from the nucleus and is more shielded, making Na’s outer electron easier to remove and resulting in a lower ionisation energy.

Question 36

Why is there a small drop from P to S?

Answer 36

With sulphur, there are 4 electrons in the 3p subshell, and the 4th is starting to doubly fill the first 3p orbital. When the second electron is added to a 3p orbital, there is a slight repulsion between the two negatively charged electrons, making the second electron easier to remove.

Question 37

What is periodicity in the context of first ionisation energy?

Answer 37

The shape of the graph for periods two and three is similar. A repeating pattern across a period is called periodicity.

Question 38

What factors control ionisation energy?

Answer 38

Many questions can be answered by application of the three factors that control ionisation energy.