Radioactivity
4 marks · EasyA neutral atom of oxygen has 8 protons, 8 neutrons, and 8 electrons.
Write down the symbol for this oxygen nucleus using atomic notation.
Give the definition of the term 'mass number'.
Explain how this atom would change if it became an isotope called oxygen-17.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a)
(b) The total number of protons and neutrons in the nucleus.
(c) Oxygen-17 would have one more neutron, so 9 neutrons but still 8 protons and 8 electrons.
Common mistakes: Wrong notation order (A and Z); Confusing mass and atomic number
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct nuclear symbol: ^{16}_8 O
B2 (b) · 1 mark · Gives definition of mass number as total protons and neutrons
B3 (c) · 1 mark · States that number of neutrons increases to 9 or mass number becomes 17
B4 (c) · 1 mark · States that number of protons remains 8 (or atomic number unchanged), or electrons remains 8
Worked solution
a) ^{16}_8 O
b) The mass number is the sum of the number of protons and neutrons in the nucleus.
c) An oxygen-17 atom would have one more neutron (9 instead of 8), but still 8 protons and 8 electrons.