Structure of the atom
The nuclear model
The protons and neutrons are found in the nucleus at the centre of the atom. The nucleus is very much smaller than the atom as a whole. The electrons are arranged in shells around the nucleus.
Properties of sub-atomic particles
ParticleRelative massRelative charge Proton 1 +1 Neutron 1 0 Electron -1
The number of electrons in an atom is always the same as the number of protons, so atoms are electrically neutral overall.
Atoms can lose or gain electrons. When they do, they form charged particles called ions:
- if an atom loses one or more electrons, it becomes a positively charged ion
- if an atom gains one or more electrons, it becomes a negatively charged ion
Atomic number and mass number
- the atoms of a particular element all have the same number…