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Question
\[\ce{^24_12Mg}\] and \[\ce{^26_12Mg}\] are symbols of isotopes of magnesium.
(a) Compare the atoms of these isotopes with respect to :
i. the composition of their nuclei
ii. their electronic configurations
(b) Give reasons why the two isotopes of magnesium have different mass numbers.
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Solution
(a) i.
|
|
\[\ce{^24_12Mg}\] |
\[\ce{^26_12Mg}\] |
|
|
|
|
|
No. of electrons |
12 |
12 |
|
No. of protons |
12 |
12 |
|
No. of neutrons |
24 - 12 = 12 |
26 - 12 = 14 |
Hence, the composition of nuclei
\[\ce{_12Mg^24->(P,n),(12+12)_12Mg^26->(p,n)(12+14)}\]
ii. Electronic configuration = 2, 8, 2
(b) Mass numbers of two isotopes of magnesium are different because of the different number of neutrons, i.e. 12 and 14, respectively.
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