Sunday, 4 January 2015

2.4 The Electronic Structure of an Atom

Electron Arrangement in an Atom
■ Structure of atom

Atoms are made up of a nucleus and electrons.

These electrons move around the nucleus of the atom.

Electrons are arranged in these shells.

This video contains information about electron arrangement in an atom.
■ Electron arrangement [electron configuration]

The way in which electrons are distributed in the shells of an atom.

The animation below shows the electron arrangement of atom.
■ Valence electrons

Definition : The electrons in the outermost shell.

Elements with the same number of valence electron have the same chemical properties.

Example of electron configuration and valence electrons.

Symbol Proton number Number of electrons Electron configuration Valence elektrons
11H 1 1 1 1
168O 8 8 2.6 6
126C 6 6 2.4 4
4020Ca 20 20 2.8.8.2 2

Worked-example 2.4(a)
Complete the following table:

Element Symbol Proton number Electron number Electron configuration Valence electrons
Helium 42He 2 2 2 2
Nitrogen 147N 7 7 2.5 5
Neon 2010Ne 10 10 2.8 8
Sodium 2311Na 11 11 2.8.1 1
Aluminium 2713Al 13 13 2.8.3 3
Argon 4018Ar 18 18 2.8.8 8
Potassium 3919K 19 19 2.8.8.1 1


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