Chemistry

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Atomic Structure

Atoms consist of electrons surrounding a nucleus that contains protons and neutrons.

Neutrons are neutral, but protons and electrons are electrically charged. Protons have a relative charge of +1, while electrons have a relative charge of -1.

The number of protons in an atom is called its atomic number. In the periodic table atoms are arranged in atomic number order.

Electrons are arranged in energy levels or shells, and different energy levels can hold different numbers of electrons. The electronic structure of an atom is a description of how the electrons are arranged, which can be shown in a diagram or by numbers. There is a link between the position of an element in the periodic table and its electronic structure.

The structure of an atom

We now know that atoms are not the smallest particles of matter. Atoms are made from smaller subatomic particles.

At the centre of an atom is a nucleus containing protons and neutrons. Electrons are arranged around the nucleus in energy levels or shells.

Both protons and electrons have an electrical charge. Both have the same size of electrical charge, but the proton is positive and the electron negative. The neutron is neutral.

Proton= +1

neutron= 0

electron= -1

The total number of electrons in an atom is always the same as the number of protons in the nucleus. This means atoms have no overall electrical charge. The number of protons in an atom is called its atomic number - also called the proton number. Atoms are arranged in the periodic table in order of increasing atomic number.