Charge in all matter

1. Electric charge is a property of matter, in the same way that mass and volume are properties of matter.
2. Every object around you, from a plastic comb to a sheet of paper to your own body, is made of matter, so every object contains electric charge.
3. There are only two types of electric charge, called positive charge and negative charge.
4. The names positive and negative are labels that tell the two types apart, and they do not mean that one type is larger, better or more important than the other.
5. Charge cannot be seen directly, so its presence is shown by its effects, such as the forces that charged objects exert on each other.
6. Charge is carried by the tiny particles that make up atoms, so explaining charge in matter starts with the structure of the atom.

Charged particles in atoms

1. Every atom has a tiny central nucleus surrounded by electrons.
2. The nucleus contains protons, which carry positive charge, and neutrons, which carry no charge.
3. The electrons occupy the space around the nucleus and carry negative charge.
4. The charge on one proton and the charge on one electron are equal in size but opposite in type.
5. This is shown with relative charges of $+1$ for a proton, $-1$ for an electron and $0$ for a neutron.
6. Because the sizes match exactly, the positive charge of one proton is cancelled completely by the negative charge of one electron.
7. An atom has the same number of electrons as protons, so the positive and negative charges inside it cancel and the atom has no overall charge.
8. For example, a carbon atom has $6$ protons and $6$ electrons, so its total charge is $(+6)+(-6)=0$.
9. The protons are locked inside the nucleus at the centre of the atom, whereas the electrons are found in the outer part of the atom.

Neutral and charged objects

1. In most objects the number of protons equals the number of electrons, so there are equal amounts of positive and negative charge.
2. The positive and negative charge cancel, so the object has a net charge of zero and is described as neutral or uncharged.
3. A neutral object still contains a vast amount of charge, and the word neutral only means that the two types are balanced.
4. A pencil, a desk and a glass of water are all neutral in everyday conditions, even though each contains billions of billions of protons and electrons.
5. An object is charged only when this balance is upset, so that one type of charge outnumbers the other.
6. An object with more positive charge than negative charge is positively charged.
7. An object with more negative charge than positive charge is negatively charged.
8. The net charge depends on the difference between the amounts of positive and negative charge, not on the total amount of charge in the object.
9. This is why a large, heavy object can be neutral while a tiny speck of dust is charged.