Question

An atom of fluorine has an atomic number of 9 and an atomic mass of 19. The atom contains

Answer 1

The number of neutrons is the difference between the mass number and the number of protons. 

You get the element by looking at the atomic number which is the number of protons. In this case, it is 9 and yes, it is F. 

However it is not an atom because it has 10 electrons so you have a fluoride ion F-. 

The number of neutrons = 19 - 9 = 10

Therefore, the answer is D.

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