Question

The red arrow is pointed at different locations of an atom of Helium. Where is it pointing to the GREATEST concentration of atomic mass?

Answer 1

The greatest concentration of atomic mass is the atom's nucleus. This is because the nucleus is made up out of protons and neutrons while the electrons surrounding the nucleus have a very small mass.

Answer 2

The most dense part of an atom is its nucleus. Almost all of the mass in an atom is made up from the protons and neutrons in the nucleus with a minimal contribution from the orbiting electrons.

Helium atom has two orbital electrons and two protons and two neutrons in nucleus. It has 4 atomic mass and 2 atomic numbers. So, the greatest concentration of atomic mass is in nucleus.