Other examples of ionic bonding
4 marks · NormalThe table shows information about four elements and their ions.
| Element | Group | Atomic number | Ion formed | Number of electrons in ion |
|---|---|---|---|---|
| Calcium | 2 | 20 | Ca2+ | |
| Chlorine | 7 | 17 | Cl– | |
| Potassium | 1 | 19 | K+ | |
| Oxygen | 6 | 8 | O2– |
Complete the column for 'Number of electrons in ion' in the table above.
Which two ions in the table are isoelectronic with argon? Give a reason for 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) Ca2+ = 18; Cl– = 18; K+ = 18; O2– = 10
(b) Ca2+ and K+ are isoelectronic with argon because both have 18 electrons, which is the same as argon.
Must show: Correct numbers for all four ions, Names of two ions isoelectronic with argon, Reason
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Marking points
A1 (a) · 1 mark · Two or three numbers in column correct
A2 (a) · 1 mark · All four numbers correct
B1 (b) · 1 mark · Identifies Ca2+ and K+ as isoelectronic with argon
B2 (b) · 1 mark · Gives a reason: same number of electrons as Ar (18) or similar
Worked solution
| Element | Group | Atomic number | Ion formed | Number of electrons in ion |
|---|---|---|---|---|
| Calcium | 2 | 20 | Ca2+ | 18 |
| Chlorine | 7 | 17 | Cl– | 18 |
| Potassium | 1 | 19 | K+ | 18 |
| Oxygen | 6 | 8 | O2– | 10 |
b: Ca2+ and K+ both have 18 electrons, which is the same as argon, so are isoelectronic.