Intro to chemistry SAQ exemplar answers

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ANSWERS TO SAQS
Subject: Chemistry / Medicine
Unit: Introduction to Chemistry/ Fundamentals of Chemistry
Topic 1: Introduction to Chemistry/ Fundamentals of Chemistry
Level: 3

SAQ 1:

1. In the table below, complete the four columns by filling the atomic
and mass numbers and symbol for the elements and the numbers
of protons, electrons and neutrons.

Element Number of Number of Number of
protons electrons neutrons

27
13 Al
11 5
B
35
29 Cu
40 20
Ca
20
19 K
56
26


Answer:
Element Number of Number of Number of
protons electrons neutrons

27 13 13 14
13 Al
11 5 5 6
5B
64 29 29 35
29 Cu
40 20 20 20
20 Ca
39 19 19 20
19 K
56 26 26 30
26 Fe




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, Subject: Chemistry / Medicine
Unit: Introduction to Chemistry/ Fundamentals of Chemistry
Topic: Introduction to Chemistry/ Fundamentals of Chemistry
Level: 3
ANSWERS TO SAQs


SAQ 2:

1. Give the electronic structure of the following elements. The atomic
number of the elements is given in brackets.
a) Lithium (3)
b) Carbon (6)
c) Argon (18)
d) Potassium (19)

2. Give the electronic structure for the following species which are
ions. These are charged particles formed by the removal
or addition of electrons to and from neutral atoms. In the case of
the magnesium ion (Mg2+) it will have had two electrons removed
from the atom. The reverse is true for the bromide ion (Br-) which
will have one electron added to the atom.
a) Lithium ion Li+
b) Oxide ion (oxygen (8)) O2-
c) Sulphide ion (sulphur (16)) S2-
d) Calcium ion (20) Ca2+


Answers:
1.
a) 1s2 2s1
b) 1s2 2s2 2p2
c) 1s2 2s2 2p6 3s2 3p6
d) 1s2 2s2 2p6 3s2 3p6 4s1 – note 4s fills before 3d
2.
a) 1s2
b) 1s2 2s2 2p6
c) 1s2 2s2 2p6 3s2 3p6
d) 1s2 2s2 2p6 3s2 3p6




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