A LevelChemistryCIETopic Questions3. Chemical Bonding3.7 Dot-&-Cross Diagrams

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First teaching 2023

First exams 2025

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Dot-&-Cross Diagrams (CIE A Level Chemistry)

Topic Questions

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11 mark

In acidic conditions, ammonia, NH3, reacts with a proton, H+, to form ammonium NH4+. 

Using the following key:

  •    N electron

 bold cross times   H electron

Which of the following Dot & Cross diagrams correctly illustrate electron movement in this reaction?

  • 1-3-e-6a

  • 1-3-e-6b

  • 1-3-e-6c

  • 1-3-e-6d

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21 mark

In which species does the underlined atom have an incomplete outer shell?

  • H3O+

  • CH3-

  • BF3

  • MgO

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11 mark

Calcium Oxide, CaO2, can be used in toothpaste as a teeth whitener. It is formed when calcium metal burns in oxygen. Which dot-and-cross diagram correctly illustrates the electron structure of the peroxide ion in CaO2.

1-3-diagram-q8h

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11 mark

Three lone pairs of electrons can be found around the central atom of which of the following ions?

  • PF6−

  • ClF2−

  • BF2−

  • SF5−

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21 mark

How many lone pairs of electrons are there in a chlorine trifluoride, ClF3, molecule?

  • 1

  • 2

  • 3

  • 0

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31 mark

Which of the following molecules obeys the octet rule?

  • BF3

  • HCN

  • BeCl2

  • CS2

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