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

Exam Questions

36 mins13 questions
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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31 mark

Ammonia, NH3, is a small covalent molecule.

How many non-bonding, outer-shell electrons are present in one molecule of ammonia?

  • 0

  • 2

  • 5

  • 6

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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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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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    21 mark

    Which of the following statements about 2-chloropropene, CH2C(Cl)CH3 is not correct

    • There are 3 lone pairs in the molecule

    • There are 24 valence electrons in the molecule 

    • The molecule does obey the octet rule

    • The molecule does not obey the octet rule

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    31 mark

    The number of electrons in the valence shell of elements X and Y are 5 and 7 respectively. What is the formula and type of compound formed from these elements?

    • Covalent, XY3

    • Ionic, XY3

    • Covalent, X3Y

    • Ionic, X3Y

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