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Question
Draw the structure of the following atoms showing the nucleus containing – protons, neutrons and the orbits with the respective electron:
Sodium [At. no. = 11, Mass no. = 23]
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Solution
Structure of atoms:

Z is Atomic Number and A is the mass number
Sodium \[\ce{^23_11Na}\]
Z = 11 = p = e
K L M
e = 11 = 2, 8, 1
A = p + n
23 = 11 + n
∴ n = 23 − 11 = 12
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