Chemistry

Chemistry

1. Atomic structure

   • An atom consits of: a poitively charged nucleus, surrounded by negatively charged electrons
   • the radius of the nucleus is much smaller than the radius of the atom
     • the nucleus contains almost all of the mass

2. Bonding

   • An ion is an atom or group of atoms with a positive or negative charge.
     • Ions form when atoms lose or gain electrons to obtain a full outer shell: metal atoms lose electrons to form positively charged ions non-metal atoms gain electrons to form negatively charged ions
       • Metal atoms lose electrons from their outer shell when they form ions: the ions formed are positive, because they have more protons than electrons the ions formed have full outer shells for elements in groups 1, 2 and 3, the number of electrons lost is the same as the group number
         • The outer shells of non-metal atoms gain electrons when they form ions: the ions formed are negative, because they have more electrons than protons the ions formed have full outer shells for groups 6 and 7, the number of electrons gained is equal to: 8 - group number