Final answer:
An atom is the fundamental unit of matter made up of a nucleus containing protons and neutrons, and an electron cloud with electrons. The nucleus holds most of the atom's mass, while the electrons occupy the majority of its volume.
Step-by-step explanation:
Current Atomic Model
The atom is the fundamental unit of matter that retains the properties of an element. A typical atom consists of a nucleus and an electron cloud. The nucleus, which contains most of the atom's mass, is composed of protons and neutrons, subatomic particles that are tightly packed together.
Protons carry a positive charge, while neutrons have no charge. Surrounding the nucleus is the electron cloud, which is where the negatively charged electrons are found, moving through this mostly empty space.
The protons and neutrons each have a mass of approximately one atomic mass unit (amu), whereas the mass of an electron is negligible in comparison.
Most of the mass of an atom is located in the nucleus due to the protons and neutrons. In contrast, the electrons, which are distributed around the nucleus, occupy most of the volume of the atom.
The identity of an atom and thereby the element it represents, is determined by the number of protons in the nucleus. Different isotopes of the same element have the same number of protons, but different numbers of neutrons.