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An atom has 7 electrons in its M-shell a...

An atom has 7 electrons in its M-shell and contains 18 neutrons in its nucleus. What is its mass number?

A

25

B

27

C

35

D

43

Text Solution

Verified by Experts

The correct Answer is:
C
An atom has 7 electrons in its M shell so, its electronic configuration=2,8 7
Atomic number = 2+8+ 7 = 17
Number of neutrons = 18
Thus, mass number = 18+ 17 = 35
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