The Role Of Electrons
Electrons don't just spin anywhere around the nucleus, they are found in shells or energy levels which are numbered 1,2,3,4 and named K,L,M and N. In an atom, the max number of electrons that can fit i each shell is. Shell 1: 2, Shell 2: 8, Shell 3: 18 and Shell 4: 32.
Atoms are electrically neutral because the number of protons are the same as the number of electrons, which balances the positive and negative charges. If this balanced is change it is called a ion. If an atom loses electrons, it becomes a positive ion and if it gains electrons, it becomes a negative ion.