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Science

Atomic structure

Electronic structure 1

The electronic structure of an atom is a description of how the electrons [electrons: Sub-atomic particles, with a negative charge and a negligible mass relative to protons and neutrons. ] are arranged. For your exam, you need to be able to describe the electronic structure of the first 20 elements in the periodic table. You may need to re-visit the section in AQA GCSE Science on the periodic table for this.

The first 20 elements in the periodic table run from hydrogen to calcium. Their electronic structures can be shown either as diagrams or numbers. You need to know how to do both.

Take lithium, for example. The drawing shows each energy level as a circle around the nucleus, with each electron represented by a dot. In the exam, do not worry about colouring in the electrons. Just make them clear and ensure they are in the right place. Sometimes you will be asked to use a cross rather than a dot. The numerical method is to write the chemical symbol (Li ) followed by the number of electrons in each energy level, innermost first, Li 2,1.

Electronic structure of lithium

ElementNumeric formatElectronsPeriodic table group

Structure of a lithium atom. A black dot represents the nucleus. The small circle around this has two red dots on it, representing the first energy level with two electrons. A larger outer circle has one red dot on it, representing the second energy level with one electron

 
Li 2,1

Lithium atoms have three electrons. Two of these fit into the first energy level, with the third in the second energy level.

Group 1

Back to Atomic structure and bonding index

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