GCSE Chemistry revision

The periodic table

AQA 4.1.2.1 Foundation & Higher

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Read on screen, then print for Cornell-style active revision.

The periodic table is read from left to right and top to bottom, with elements arranged in order of increasing atomic number.
The atomic number, found in the bottom left of each element box, tells you the number of protons in the atoms of that element.
The mass number, found in the top left, gives the total number of protons and neutrons in an atom.
The elemental symbol, on the right of each box, is a one or two letter abbreviation for the element, for example Na for sodium.

1. How to Read the Periodic Table AQA

The periodic table is read from left to right and top to bottom, with elements arranged in order of increasing atomic number.
The atomic number, found in the bottom left of each element box, tells you the number of protons in the atoms of that element.
The mass number, found in the top left, gives the total number of protons and neutrons in an atom.
The elemental symbol, on the right of each box, is a one or two letter abbreviation for the element, for example Na for sodium.

Elements in the same group have the same number of electrons in their outermost shell, which is what gives them similar chemical properties.
The group number directly tells you how many electrons each element in that group has in its outer shell.
All elements in a group have different total numbers of electrons, but share the same number of outer shell electrons.

2. Electrons in the Outer Shell AQA

Elements in the same group have the same number of electrons in their outermost shell, which is what gives them similar chemical properties.
The group number directly tells you how many electrons each element in that group has in its outer shell.
All elements in a group have different total numbers of electrons, but share the same number of outer shell electrons.

Group 1 elements are called the alkali metals and each has one electron in its outer shell.
All alkali metals react violently with water due to their single outer shell electron.
Reactivity increases as you go down group 1, so caesium is more reactive than lithium.

Group 7 elements are called the halogens and each has seven electrons in its outer shell.
Unlike the alkali metals, the halogens become less reactive as you go down the group.

Group 0 elements are called the noble gases and all have completely full outer electron shells.
Helium has two electrons filling its single shell, whilst argon has eight electrons filling its outer shell.
Because their outer shells are full, noble gases do not need to gain or lose electrons, making them very unreactive.

5. Group 0 – The Noble Gases AQA

Group 0 elements are called the noble gases and all have completely full outer electron shells.
Helium has two electrons filling its single shell, whilst argon has eight electrons filling its outer shell.
Because their outer shells are full, noble gases do not need to gain or lose electrons, making them very unreactive.