Everything Science Grade 10

CHAPTER 4. THE ATOM 4.6

Electronic configuration ESABE

The energy of electrons ESABF

The electrons of an atom all have the same charge and the same mass, but each electron

has a different amount ofenergy. Electrons that have thelowestenergy are found closest

to the nucleus (where the attractive force of the positively charged nucleus is the greatest)

and the electrons that havehigherenergy (and are able to overcome the attractive force of

the nucleus) are found further away.

See video: VPama at http://www.everythingscience.co.za

Electron arrangement ESABG

We will start with a very simple view of the arrangement or configuration of electrons

around an atom. This view simply states that electrons are arranged in energy levels (or

shells) around the nucleus of an atom. These energy levels are numbered 1 , 2 , 3 , etc.

Electrons that are in the first energy level (energy level 1 ) are closest to the nucleus and will

have the lowest energy. Electrons further away from the nucleus will have a higher energy.

In the following examples, the energy levels are shown as concentric circles around the

central nucleus. The important thing to know for these diagrams is that the first energy

level can hold 2 electrons, the second energy level can hold 8 electrons and the third

energy level can hold 8 electrons.

1 .Lithium

Lithium (Li) has an atomic number

of 3 , meaning that in a neutral atom,

the number of electrons will also be

3. The first two electrons are found

in the first energy level, while the

third electron is found in the second

energy level (Figure 4.6).

second energy level

first energy level

electrons

nucleus, containing 3 pro-

tons and 4 neutrons

Figure 4.6: Electron arrangement of a lithium atom.

Chemistry: Matter and Materials 79