(N/A) There is no direct practical way to measure the size or volume of an individual atom because the electron cloud does not have a sharp boundary.
However,the size of an atom can be estimated by measuring the distance between atoms in a bonded state. The three common methods are:
$1$. Metallic radius: Used for metals,defined as half the internuclear distance between two adjacent metal atoms in a metallic lattice.
$2$. Covalent radius: Used for non-metals,defined as half the distance between the nuclei of two atoms bonded by a single covalent bond.
$3$. Van der Waals radius: Used for noble gases and non-bonded atoms,defined as half the distance between the nuclei of two identical non-bonded atoms in a solid state.