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

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.

it means there are 3 atoms of oxygen

answers: to make sure that all of the broken pieces of tablet were added to the water, to allow for fair comparison of all three trials, with different particle sizes to avoid experimental error