The radius of an atom with a heavy nucleus is not necessarily larger than the radius of an atom with a lighter nucleus. The size of an atom is primarily determined by the distribution of its electrons, rather than the mass of its nucleus.
In an atom, electrons are arranged in orbitals or energy levels around the nucleus. These orbitals define the region where an electron is most likely to be found. The size of an atom is typically measured as the distance from the nucleus to the outermost electron orbital, known as the atomic radius.
The atomic radius can vary across different elements, but it is generally influenced by the number of electron shells and the effective nuclear charge experienced by the outermost electrons. The effective nuclear charge is determined by the number of protons in the nucleus and the shielding effect of inner electron shells.
While heavy nuclei have more protons than lighter nuclei, leading to a greater effective nuclear charge, this does not necessarily result in larger atomic radii. The distribution of electrons and the overall atomic structure play crucial roles in determining the size of an atom.
It's worth noting that within a given element, the size of the atom may increase as you move down a group in the periodic table. This is due to the addition of more electron shells, which increases the atomic radius. However, comparing the sizes of atoms with heavy nuclei to those with lighter nuclei requires consideration of various factors and cannot be generalized solely based on nuclear mass.