Question

An atom with 9 protons and 10 neutrons in its nucleus and 9 electrons in movement around the nucleus would be an atom of which element?
A: Beryllium
B: Neon
C: Fluorine
D: Potassium

Answer 1

Answer: The element is Fluorine.

Explanation:

Atomic number is defined as the number of protons or electrons that are present in a neutral atom.

Atomic number = number of protons = number of electrons

Atomic mass is defined as the sum of number of protons and neutrons that are present in an atom.

Atomic mass = Number of protons + Number of neutrons

We are given:

Number of protons = 9 = Atomic number

Number of electrons = 9

Number of neutrons = 10

Mass number = 9 + 10 = 19

The element having atomic number equal to 9 and mass number equal to 19 is fluorine.

Hence, the element is Fluorine.

Answer 2

The correct answer is C.  We know this is true since the number of protons an atom has is its atomic number.  Since this atom  has 9 protons, look for the element on the periodic table that has an atomic number of 9.  The element that has an atomic number of 9 is flouring.

I hope this helps.