Other examples of ionic bonding
5 marks · HardPhosphorus is a Group 5 element with atomic number 15.
Describe how a phosphorus atom forms a phosphide ion ().
Write the electronic configuration of a phosphide ion.
Explain why the phosphide ion is isoelectronic with a noble gas atom. Name the noble gas.
State the total number of electrons in a phosphide ion.
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) It gains 3 electrons
(b) [2, 8, 8]
(c) It has the same number and arrangement of electrons as an argon atom (Ar)
(d) 18
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Marking points
B1 (a) · 1 mark · States that a phosphorus atom gains 3 electrons to form a phosphide ion.
B2 (b) · 1 mark · Electronic configuration given as [2, 8, 8].
M1 (c) · 1 mark · Explains that the ion has the same number and arrangement of electrons as a noble gas atom.
A1 (c) · 1 mark · Names argon as the noble gas.
B3 (d) · 1 mark · States that the ion has 18 electrons.
Worked solution
a) A phosphorus atom forms a phosphide ion by gaining 3 electrons.
b) Electronic configuration of phosphide ion: [2, 8, 8]
c) The phosphide ion has the same number and arrangement of electrons as a noble gas atom, because after gaining 3 electrons (total 18), it matches the electron configuration of argon (Ar).
d) The total number of electrons in a phosphide ion is 18.