1a. Atoms are made of
fundamental particles called
(+),
(0) and
(-).
1b. The mass of proton is
, the mass of a neutron is
and the mass of an electron is ~
.
1c. The centre of the atom is called the
.
1d. It consists of
and neutrons and contains most of the mass of the atom.
2a. The number of protons in the atom is called the
. It also equals the number of
in a neutral atom.
2b. The
is the sum of the protons and neutrons in the nucleus.
3. An atom of mass number 43, and atomic number 21, consists of
protons,
neutrons and
electrons.
4a. The
is defined as the sum of the protons plus neutrons in the
.
4b. In the symbol for an atom of
shown on the left, the atom consists of
protons,
neutrons and
electrons.
4c. Atoms of the same element with a different
due to different numbers of neutrons are called
.
5a.
Both of these atoms of
have
protons and
electrons, but the left atom has
neutrons and the right atom has
neutrons.
5b. The
of an element is defined as the
of all the atoms present in an element compared to the mass of a carbon-12 atom (designated 12.000 atomic mass units).