Clouds of electrons in the atom.

Scientists believe that there is a tiny particle, called the nucleus, at the centre of every atom. 

The nucleus is positively charged, due to positive particles called protons found inside it.
Each nucleus is coated with a cloud that's made up of at least one negatively charged electron. The attraction of opposite charges keeps the electron cloud around the nucleus.

The negative charge of an electron just cancels the positive charge of a proton. 
This means that in every uncharged atom there are the same number of electrons surrounding the nucleus as there are protons inside the nucleus.