Topic 1 – Atomic Structure and the Periodic Table
In order to develop their practical skills, students should be encouraged to carry out a range of practical experiments related to this topic. Possible
experiments include the use of hand-held spectroscopes to investigate spectra from flame tests. Mathematical skills that could be developed in this
topic include calculating a relative atomic mass from isotopic composition data, using simple probability to calculate the peak heights for the mass
spectrum of chlorine molecules, using logarithms to compare successive ionisation energies for an element. Within this topic, students can consider
how models for the atom have developed over time, as new evidence has become available. They can also consider how data is used to investigate
relationships, such as between the magnitude of ionisation energy and the structure of an atom.
1. know the structure of an atom in terms of electrons, protons and neutrons
2. know the relative mass and relative charge of protons, neutrons and electrons
Subatomic Particle Charge Relative Mass Whereabouts
Proton Positive (+1) 1 Nucleus
Neutron Neutral (0) 1 Nucleus
Electron Negative (-1) 1/1840 Orbiting in electron shells
3. know what is meant by the terms ‘atomic (proton) number’ and ‘mass number’
What is the difference between an atom’s mass number and atomic number?
Mass number = number of protons + number of neutrons // Atomic number = number of protons
4. be able to determine the number of each type of sub-atomic particle in an atom, molecule or ion from the
atomic (proton) number and mass number
Give the number of subatomic particles (p, n, e-) in an isotope of Carbon-12.
6 protons, 6 neutrons, 6 electrons.
5. understand the term ‘isotopes’
Give the definition of an isotope.
Isotopes are atoms of the same element with the same number of protons, but different numbers of neutrons.
6. be able to define the terms ‘relative isotopic mass’ and ‘relative atomic mass’, based on the 12C scale
What is the definition of ‘relative isotopic mass’? Therefore, what is the definition of ‘relative atomic mass’?
RIM is the mass of one atom of an isotope, relative to 1/12th of the mass of a 12C atom.
RAM is the weighted average mass (WhAM) of an atom of an element, relative to 1/12th of the mass of a 12C atom.
, 7. understand the terms ‘relative molecular mass’ and ‘relative formula mass’, including calculating these
values from relative atomic masses. Definitions of these terms will not be expected. The term ‘relative formula mass’
should be used for compounds with giant structures.
Find the relative formula mass of Na2CO3•10H2O.
(23x2) + (12x1) + (16x3) + (10x18) = 286
8. be able to analyse and interpret data from mass spectrometry to calculate relative atomic mass from
relative abundance of isotopes and vice versa
What is the purpose of the electric field?
To accelerate the ions.
What is the purpose of the magnetic field?
To deflect the ions.
From this graph, predict the RAM of boron.
(10x20) + (11x80) / 100 = 10.8
9. be able to predict the mass spectra, including relative peak heights, for diatomic molecules, including Cl
From this graph, predict the RAM of chlorine.
(75x35)+(25x37)/100 = 35.5
Explain the identity of each of the peaks.
35 = 35Cl+ (3:1) 37 = 37Cl+ (here the diatomic bond is broken)
70 = 35Cl+ + 35Cl+ 72 = 35Cl+ + 37Cl+ 74 = 37Cl+ + 37Cl+ (Cl2 9:6:1)
10. understand how mass spectrometry can be used to determine the relative molecular mass of a molecule.
Limited to the m/z value for the molecular ion, M+, giving the relative molecular mass of the molecule.
Find the M+ value from this graph.
Here, the M+ is 72 – always look for the furthest
right peak (regardless of how small it is!!)
2
In order to develop their practical skills, students should be encouraged to carry out a range of practical experiments related to this topic. Possible
experiments include the use of hand-held spectroscopes to investigate spectra from flame tests. Mathematical skills that could be developed in this
topic include calculating a relative atomic mass from isotopic composition data, using simple probability to calculate the peak heights for the mass
spectrum of chlorine molecules, using logarithms to compare successive ionisation energies for an element. Within this topic, students can consider
how models for the atom have developed over time, as new evidence has become available. They can also consider how data is used to investigate
relationships, such as between the magnitude of ionisation energy and the structure of an atom.
1. know the structure of an atom in terms of electrons, protons and neutrons
2. know the relative mass and relative charge of protons, neutrons and electrons
Subatomic Particle Charge Relative Mass Whereabouts
Proton Positive (+1) 1 Nucleus
Neutron Neutral (0) 1 Nucleus
Electron Negative (-1) 1/1840 Orbiting in electron shells
3. know what is meant by the terms ‘atomic (proton) number’ and ‘mass number’
What is the difference between an atom’s mass number and atomic number?
Mass number = number of protons + number of neutrons // Atomic number = number of protons
4. be able to determine the number of each type of sub-atomic particle in an atom, molecule or ion from the
atomic (proton) number and mass number
Give the number of subatomic particles (p, n, e-) in an isotope of Carbon-12.
6 protons, 6 neutrons, 6 electrons.
5. understand the term ‘isotopes’
Give the definition of an isotope.
Isotopes are atoms of the same element with the same number of protons, but different numbers of neutrons.
6. be able to define the terms ‘relative isotopic mass’ and ‘relative atomic mass’, based on the 12C scale
What is the definition of ‘relative isotopic mass’? Therefore, what is the definition of ‘relative atomic mass’?
RIM is the mass of one atom of an isotope, relative to 1/12th of the mass of a 12C atom.
RAM is the weighted average mass (WhAM) of an atom of an element, relative to 1/12th of the mass of a 12C atom.
, 7. understand the terms ‘relative molecular mass’ and ‘relative formula mass’, including calculating these
values from relative atomic masses. Definitions of these terms will not be expected. The term ‘relative formula mass’
should be used for compounds with giant structures.
Find the relative formula mass of Na2CO3•10H2O.
(23x2) + (12x1) + (16x3) + (10x18) = 286
8. be able to analyse and interpret data from mass spectrometry to calculate relative atomic mass from
relative abundance of isotopes and vice versa
What is the purpose of the electric field?
To accelerate the ions.
What is the purpose of the magnetic field?
To deflect the ions.
From this graph, predict the RAM of boron.
(10x20) + (11x80) / 100 = 10.8
9. be able to predict the mass spectra, including relative peak heights, for diatomic molecules, including Cl
From this graph, predict the RAM of chlorine.
(75x35)+(25x37)/100 = 35.5
Explain the identity of each of the peaks.
35 = 35Cl+ (3:1) 37 = 37Cl+ (here the diatomic bond is broken)
70 = 35Cl+ + 35Cl+ 72 = 35Cl+ + 37Cl+ 74 = 37Cl+ + 37Cl+ (Cl2 9:6:1)
10. understand how mass spectrometry can be used to determine the relative molecular mass of a molecule.
Limited to the m/z value for the molecular ion, M+, giving the relative molecular mass of the molecule.
Find the M+ value from this graph.
Here, the M+ is 72 – always look for the furthest
right peak (regardless of how small it is!!)
2
