All atoms are neutral means that the number of protons and electrons in an atom are equal. Protons have a positive charge, while electrons have a negative charge. When the number of protons and electrons are equal, the atom has a net charge of zero and is said to be neutral.

For example, a carbon atom has six protons and six electrons. The positive charges of the protons cancel out the negative charges of the electrons, so the carbon atom is neutral.

Atoms can become charged if they lose or gain electrons. For example, if a carbon atom loses one electron, it will have seven protons and five electrons. The positive charges of the protons will outweigh the negative charges of the electrons, so the carbon atom will have a net positive charge and will be said to be a positive ion.

Atoms can also become charged if they gain electrons. For example, if a carbon atom gains one electron, it will have six protons and seven electrons. The negative charges of the electrons will outweigh the positive charges of the protons, so the carbon atom will have a net negative charge and will be said to be a negative ion.

The neutrality of atoms is important for the stability of matter. If atoms were not neutral, they would be attracted to each other with very strong forces, and the universe would be a chaotic place.