
(1) All substances are made up of basic units called
, which are themselves made from three different
.
(2) In the centre of an atom is the
consisting of
charged
and neutral
.
(3) Moving around the
are
charged
in specific energy levels you can simply envisage as '
'.
(4) Particular types of atoms are called
and all the atoms of one type have the same number of
in the central
, which is called the
.