The arrangement of the electrons in an atom
4 marks · NormalA student writes the following table for three elements.
| Element | Atomic number |
|---|---|
| Nitrogen | 7 |
| Calcium | 20 |
| Aluminium | 13 |
Answer the following questions about the electronic configurations of these elements.
What is the electronic configuration for nitrogen?
What is the electronic configuration for aluminium?
Give the electronic configuration for calcium.
Which of these elements has the greatest number of electron shells? 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.
Show answer
(a) 2,5
(b) 2,8,3
(c) 2,8,8,2
(d) Calcium, because it has 4 shells.
Also accept: Accept comma or space as separator in configurations.
Common mistakes: Wrong number of electrons in shells; Not explaining shell count
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correct configuration for nitrogen (2,5 or 2 5).
B1 (b) · 1 mark · Correct configuration for aluminium (2,8,3 or 2 8 3).
B1 (c) · 1 mark · Correct configuration for calcium (2,8,8,2 or 2 8 8 2).
M1 (d) · 1 mark · Identifies calcium as having the most shells and gives appropriate explanation.
Worked solution
a. Nitrogen has atomic number 7: configuration is 2,5.
b. Aluminium has atomic number 13: 2,8,3.
c. Calcium has atomic number 20: 2,8,8,2.
d. Calcium, because it has four shells (2,8,8,2), the greatest number among the three elements.