The periodic table

3 marks · Normal

Copper has two naturally occurring isotopes: copper-63 and copper-65.

Explain how you can use the periodic table to determine the numbers of protons, neutrons, and electrons in an atom of copper-65. State the actual numbers for each subatomic particle.

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The atomic number of copper from the periodic table is 29, so an atom of copper-65 has 29 protons and 29 electrons. The number of neutrons is 65 - 29 = 36.

Must show: States atomic number of Cu is 29, States protons = 29, States electrons = 29, Calculates neutrons = 36

Also accept: Atomic number for copper is 29; protons and electrons are both 29; neutrons = 65 - 29 = 36

Common mistakes: Uses mass number for protons; Forgets to subtract for neutrons

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Marking points

B1 · 1 mark · States or uses atomic number = 29 for copper (can be implied)

M1 · 1 mark · Number of protons and electrons correctly given as 29 for copper-65

A1 · 1 mark · Calculates number of neutrons as 36 (65 - 29)

Worked solution

From the periodic table, copper has atomic number 29.

This tells us there are 29 protons and, for a neutral atom, 29 electrons.

Neutrons = mass number - atomic number = 65 - 29 = 36.