Answer:
A) nucleus, smaller
Explanation:
The structure of an atom can be explained based on Rutherford's model according to which, most of the mass of an atom is concentrated in its positively charged core called the 'nucleus' whereas the negatively charged electrons move around it in fixed paths called orbits. The radius of the nucleus however is much smaller than that on the atom.
An element is usually represented in terms of its atomic mass (A) and atomic number(Z).
Atomic mass = protons + neutrons
Atomic number = number of protons
Therefore, the __nucleus_______ contains the majority of the mass of the atom but is much _smaller_______ than the atom.
