Other examples of ionic bonding
3 marks · NormalPhosphorus (P) forms an ion with the same number of electrons as argon (Ar).
Explain how this is possible. In your answer, include:
The change in electron number
The charge on the ion
A reason why phosphorus forms this ion
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(a) Phosphorus gains 3 electrons (goes from 15 to 18 electrons).
(b) 3–
(c) Because by gaining 3 electrons, phosphorus achieves a noble gas configuration like argon.
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Marking points
B1 (a) · 1 mark · Correctly explains phosphorus gains 3 electrons to reach argon's electron number
B2 (b) · 1 mark · Correctly identifies ion charge as 3–
B3 (c) · 1 mark · Explains why: to achieve a noble gas configuration
Worked solution
a: Phosphorus has 15 electrons as a neutral atom. To match argon (18 electrons), it must gain 3 electrons.
b: It forms a 3– ion (P3–).
c: This allows it to achieve a noble gas electron configuration, making it more stable.