The arrangement of the electrons in an atom
3 marks · NormalCopper (Cu) and neon (Ne) are two elements found in the Periodic Table.
Copper is found in Group 11 and Period 4. Neon is found in Group 0 and Period 2.
Explain how the information about group and period allows you to deduce the atomic numbers of copper and neon.
State what the group number and period number tell you about an element's position in the Periodic Table.
Using the Periodic Table, deduce the atomic number of neon (Ne).
Using the Periodic Table, deduce the atomic number of copper (Cu).
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) The group number shows the number of electrons in the outer shell (for main groups), and the period number shows the number of electron shells (energy levels).
(b) The atomic number of neon is 10.
(c) The atomic number of copper is 29.
Common mistakes: Incorrect group or period definition; Atomic mass confused with atomic number; Incorrect atomic number for either element
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Relates group number to outer electrons and period number to electron shells; or gives correct principles.
B2 (b) · 1 mark · Atomic number of neon correctly given as 10.
B3 (c) · 1 mark · Atomic number of copper correctly given as 29.
Worked solution
(a) The group number tells us how many electrons are in the outer shell (for Groups 1–2 and 0, and groups 3–7 in simple cases), and the period number tells us how many energy levels (electron shells) the atom has.
(b) Neon is found in period 2 and group 0. The atomic numbers in period 2 range from lithium (3) to neon (10). Therefore, neon has atomic number 10.
(c) Copper is in period 4, group 11 (transition metal). The atomic numbers in period 4 start at potassium (19) and increase across the period. Copper is the eleventh element in period 4, so its atomic number is 29.