Answer:
down
Step-by-step explanation:
The atomic number is the number of protons in the nucleus of an atom. The number of protons define the identity of an element (i.e., an element with 6 protons is a carbon atom, no matter how many neutrons may be present).
An atom consists of electrons, protons, and neutrons. The protons and neutrons are present inside the nucleus of an atom whereas the electrons revolve around the nucleus of an atom.
The number of protons in an atom represents the atomic number of that particular atom. Further, this atomic number determines the place of each atom in the periodic table and its chemical properties.
For example, the mass number of sodium atom is 23 that is number of protons and neutrons. The atomic number of sodium is 11 that means there are 11 protons. The number of neutrons will be 23 - 11 = 12.