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"

the grams   of   barium that   are in   2.3 x 10^23   atoms of barium   is   52.4 g (answer c)

    calculation

mass = moles   of ba   x molar   mass of ba

  molar mass of ba from periodic table=   137.3 g/mol

  use the   avogadro's law   constant   to   calculate the moles of barium

  that   is     1 mole =   6.02   x 10^23 atoms

                    ? moles = 2.3 x 10^23   atoms

by cross   multiplication

=(1 mole   x 2.3x 10^23 atoms)   / 6.02   x10^23 atoms)=   0.382   moles

mass   is therefore = 137.3   g/mol x 0.382 mol = 52.4 ( answer c)

explanation: