What one characteristic of an atom determines what type of element it is?

the number of neutrons.
the number of protons.
the mass number.
the atomic mass.

the number of protons.

Explanation:

The number of protons is also the atomic number that the element has in the periodic table, no element has the same number of protons than any other, and if an atom changes the number of protons in its nucleus it changes the element it is. This gives the atom its characteristics, and its position in the periodic table, this also dictates the type of element that that atom is.

the potential energy of the reactants is 200j.

from the energy diagram, the energy of the product formed is 350j; this means that, this reaction is an endothermic reaction, because it absorbs energy from its environment.

the positions which points up in upward carbon and down in downward carbon are axial

and vice versa holds true for equatorial positions

so the correct answer with labelled diagram will be