© 2024 Daniel Day (Science for Oxbridge). All Rights Reserved.
ESAT: Chemistry Notes
Prepare for ESAT with concise and comprehensive notes on the
whole biology speci cation
1. Atomic structure
Atom
1. Central nucleus of protons and neutrons surrounded by electrons in energy levels
2. Most mass in nucleus
3. Volume of nucleus very small compared to volume of atom
4. Mostly empty space
5. Electrons in shells of increasing energy (1st shell: 2 electrons; 2nd shell 8 electrons;
3rd shell: 18 electrons)
Proton: relative mass = 1, charge = +1
Neutron: relative mass = 1, charge = 0
Electron: relative mass = 0 (negligible), charge = -1
Atomic Number: number of protons in the nucleus (and number of electrons in neutral atom)
Mass Number: sum of protons and neutrons in the nucleus
Isotopes: atoms of the same element with the same number of protons but different number
of neutrons
Mass spectrometry
1. Used to determine relative abundance and mass of different chemical species, such as
isotopes
2. Mass spectrum: relative abundance on y-axis; mass/charge (m/z) on x-axis
3. Mass/charge = mass (if z = +1); assume z = +1 unless context suggests otherwise
4. Mass/charge x charge = mass (if z ≠+1)
Relative atomic mass (Ar): weighted average mass of an element’s isotopes compared to
1/12th mass of Carbon-12
© 2024 Daniel Day. All Rights Reserved. This document is protected by copyright law. Unauthorised reproduction, distribution, or use of any part of this
material is strictly prohibited. 1 of 21
fi
ESAT: Chemistry Notes
Prepare for ESAT with concise and comprehensive notes on the
whole biology speci cation
1. Atomic structure
Atom
1. Central nucleus of protons and neutrons surrounded by electrons in energy levels
2. Most mass in nucleus
3. Volume of nucleus very small compared to volume of atom
4. Mostly empty space
5. Electrons in shells of increasing energy (1st shell: 2 electrons; 2nd shell 8 electrons;
3rd shell: 18 electrons)
Proton: relative mass = 1, charge = +1
Neutron: relative mass = 1, charge = 0
Electron: relative mass = 0 (negligible), charge = -1
Atomic Number: number of protons in the nucleus (and number of electrons in neutral atom)
Mass Number: sum of protons and neutrons in the nucleus
Isotopes: atoms of the same element with the same number of protons but different number
of neutrons
Mass spectrometry
1. Used to determine relative abundance and mass of different chemical species, such as
isotopes
2. Mass spectrum: relative abundance on y-axis; mass/charge (m/z) on x-axis
3. Mass/charge = mass (if z = +1); assume z = +1 unless context suggests otherwise
4. Mass/charge x charge = mass (if z ≠+1)
Relative atomic mass (Ar): weighted average mass of an element’s isotopes compared to
1/12th mass of Carbon-12
© 2024 Daniel Day. All Rights Reserved. This document is protected by copyright law. Unauthorised reproduction, distribution, or use of any part of this
material is strictly prohibited. 1 of 21
fi
