Drawing diagrams of electronic configurations
4 marks · NormalThe diagrams below show the electronic configurations of two different elements, X and Y:
How many electrons are there in element X?
How many electrons are there in element Y?
State the number of shells in element X and the number of electrons in its outer shell.
Which of the two elements, X or Y, is likely to be more reactive? Explain your answer.
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.
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(a) 7
(b) 10
(c) 2 shells, 5 electrons in outer shell · must show States 2 shells, States 5 electrons in outer shell
(d) X is likely to be more reactive because it has 5 outer electrons and needs to gain 3 to fill its shell, whereas Y already has a full outer shell and is very stable. · must show Identifies X or Y, Reason linked to outer shell electrons or full shell stability
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correctly counts total electrons in X (2 + 5 = 7).
M2 (b) · 1 mark · Correctly counts total electrons in Y (2 + 8 = 10).
B1 (c) · 1 mark · States number of shells and electrons in X outer shell (2 shells, 5 electrons).
E1 (d) · 1 mark · Correctly compares reactivity, with supporting explanation (Y has full shell, X has incomplete shell so more reactive).
Worked solution
a) Number of electrons in X = 2 (first shell) + 5 (second shell) = 7 electrons.
b) Number of electrons in Y = 2 (first shell) + 8 (second shell) = 10 electrons.
c) Number of shells in X = 2; outer shell electrons = 5.
d) X is more reactive because it does not have a full outer shell, while Y's outer shell is full and stable.