The central core of an atom is called the
a. reactor vessel.
b. neutron.
c. proton.
d. nucleus.

The central portion is called neutron.

Explanation:

An atom has a central part known as nucleus and outer shells.

The central nucleus contains protons (the positively charged sub atomic particle) and neutrons (the neutral sub atomic particle).

The outer portion has negatively charged sub atomic particle known as electrons.

The atomic number of an element is the number of protons present in the nucleus.

The Answer is Nucleus

Explanation:

The Nuleus is the brain of the atom always like the "boss"

each  column  of the  table  is called a group. elements in a group share similar properties. groups are  read  from  top  to  bottom. metal. metalloid. nonmetal. solid. liquid. gas. fe. hg. o.  2. 3. 4. 5. 6. 7. 8. 9.  2. beryllium. 9.012. 4.  sodium. 22.990.  11. 3.  magnesium. 24.305.  12.  potassium. 39.098.  19. 4.  calcium. 40.078.  20. i guess  i