What is a covalent bond?
2 marks · EasyA phosphorus atom has 5 electrons in its outer shell. How many covalent bonds can it form in a molecule of phosphorus trichloride (PCl3)?
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3 (±0)
Common mistakes: Giving 5 instead of 3
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Marking points
M1 · 1 mark · Works out that P needs to share 3 more electrons to have 8 in its outer shell.
A1 · 1 mark · Gives the correct answer: 3 covalent bonds.
Worked solution
Phosphorus has 5 electrons in its outer shell. It needs 3 more to reach 8 (the noble gas configuration):
So, phosphorus forms 3 covalent bonds in PCl3.