Everything Science Grade 10

CHAPTER 4. THE ATOM 4.6

DEFINITION: Valence electrons

The electrons in the outermost energy level of an atom

DEFINITION: Core electrons

All the electrons in an atom, excluding the valence electrons

Exercise 4 - 4

Complete the following table:

Element or Ion Electron configuration Core electrons Valence electrons

Potassium (K)

Helium (He)

Oxygen ion (O^2 −)

Magnesium ion (Mg2+)

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The importance of understanding electron

configuration

ESABL

By this stage, you may well be wondering why it is important for you to understand how
electrons are arranged around the nucleus of an atom. Remember that during chemical

Chemistry: Matter and Materials 87