The Periodic Table

5 marks · Easy

This question is about the arrangement of electrons in atoms and representing them with diagrams.

(a)

State what the vertical columns and horizontal rows in the Periodic Table are called.

[2 marks]

(b)

Phosphorus has atomic number 15. Write its electronic configuration using numbers separated by commas.

[1 mark]

(c)

Draw a diagram to show the arrangement of electrons in a phosphorus atom. Use circles for shells and crosses (×) for electrons.

[2 marks]

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) Vertical columns: groups; Horizontal rows: periods

(b) 2,8,5

Common mistakes: Confusing groups and periods; wrong arrangement such as 2,8,5 for phosphorus

Show mark scheme and worked solution

Marking points

B1 (a) · 1 mark · Correctly identifies vertical columns as 'groups'.

B2 (a) · 1 mark · Correctly identifies horizontal rows as 'periods'.

B3 (b) · 1 mark · Correctly gives phosphorus electronic configuration as 2,8,5.

B4 (c) · 1 mark · Diagram shows 3 shells with correct number of electrons in each shell (2-8-5).

B5 (c) · 1 mark · Uses crosses (×) for electrons and circles for shells.

Worked solution

a) In the Periodic Table, the vertical columns are called groups and the horizontal rows are called periods.

b) Atomic number of phosphorus = 15, so electron arrangement: 2 electrons in 1st shell, 8 in 2nd, 5 in 3rd. Electronic configuration: 2,8,5.

c) Diagram: Draw three concentric circles (shells). Place 2 crosses (×) on the first shell, 8 on the second, 5 on the third.