c) What does the number on the upper right represent and which subatomic particle can change this number (but not the symbol for the element!!)? Support your answer with a specific example from the simulation.

Explanation:

The number on the upper right represents the mass number.

  Mass number is the number of protons and neutrons that makes up an atom.

Mass number simply denotes the number of particles in the nucleus of an atom.

  Mass number  = number of protons + number of neutrons

Number of protons is the number of positively charged particles in the atom

Number of neutrons is the number of uncharged particles.

 When the number of protons or number of neutrons changes, the mass number will change.

  For example;

                   O¹⁶₈

 Mass number = 16

 Atomic number = 8