Q1(a) Atoms are made of
fundamental particles called protons (+),
(0) and
(-). (b) The centre of the atom is called the
. (c) It consists of protons and
and contains most of the mass of the atom.
Q2(a) The number of protons in the atom is called the
number. It also equals the number of
in a neutral atom. (b) The
is the sum of the protons and neutrons in the nucleus.
Q3 An atom of mass number 43, and atomic number 21, consists of
protons,
neutrons and
electrons.
Q4 (a) In the symbol for an atom of
shown on the left, the atom consists of
protons,
neutrons and
electrons. (b) Atoms of the same element with a different
number due to different numbers of neutrons are called
.
Q5(a) Electrons are arranged around the nucleus in energy levels or
. (b) The 1st shell can have a maximum of
electrons, the
shell a maximum of
electrons and the 3rd shell a maximum of
electrons. (c) The 19th and 20th electrons go in the
shell. (d) The electron arrangement, showing the number of electrons in each
can be written out in shorthand eg 2.8.6 for the 1st, 2nd and 3rd shells respectively.
Q6(a) Apart from hydrogen and
in period 1 of the Periodic Table the last number in the arrangement is equal to the
number in the Periodic Table. (b) The number of shells used containing electrons is equal to the
number. (c) The number of electrons in an atom is equal to the
or proton number.
Q7(a) The element
has an atomic number of 15 so the atoms have
protons or 15
. (b) The electron arrangement will be
. (c) In the Periodic Table it will be a member of Group
and it will be the
element along Period
.
Q8(a) Fluorine has an atomic number of
so the atoms have 9 protons or electrons. (b) Its electron arrangement is
and it belongs to Group
on Period
.