Atomic Structure

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Atomic structure

Atoms are made up of three

smaller particles called protons, neutrons and electrons. Table 3.1 shows the

mass and electric charge of these particles. The mass is shown as relative

mass, which is the mass of the particle compared to a proton.

At the centre of the atom is a

tiny nucleus, which is far smaller than the atom. The nucleus contains protons

and neutrons, and so most of the mass of the atom is in the nucleus. Outside

the nucleus are electrons which orbit the nucleus in shells.

Atoms are neutral because they

contain the same number of electrons, which are negatively charged, and protons

which are positively charged.