Electronic configurations and the periodic table
3 marks · EasyThe table shows electronic configurations for four elements.
| Element | Electronic configuration |
|---|---|
| Q | 2,8,5 |
| R | 2,8,8,2 |
| S | 2,5 |
| T | 2,8,3 |
Which element is in Period 2?
Which element is in Group 5?
State the number of electrons in the outer shell of element R.
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) S
(b) Q
(c) 2
Common mistakes: Miscounting shells or outer electrons
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Marking points
A1 (a) · 1 mark · Identifies element S (with two shells) as Period 2.
A2 (b) · 1 mark · Identifies element Q (with 5 outer electrons) as Group 5.
A3 (c) · 1 mark · States that R has 2 electrons in its outer shell.
Worked solution
a) Period 2 elements have 2 shells. S has configuration 2,5, so S is in Period 2.
b) Group 5 elements have 5 electrons in the outer shell. Q has outer shell of 5, so Q is in Group 5.
c) R's outer shell is 2 electrons (2,8,8,2).