Question

For Al, its atomic number is 13 and its mass number is 27. How many neutrons does it have? A. 13 B. 14 C. 26 D. 27 E. 40

Answer 1

14

Step-by-step explanation:

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Answer 2

B. 14

Step-by-step explanation:

For an element:

- Atomic number: is the number of protons in the nucleus (p)

- Mass number: it is the number of protons (p) + neutrons (n) in the nucleus

For Al (aluminium), we have:

p = 13

p + n = 27

Substituting the first equation into the second one, we find the number of neutrons:

n = 27 - p = 27 - 13 = 14