What is the basic unit of matter that defines each element?

What is the basic unit of matter that defines each element?

• A. Molecule
• B. Ion
• C. Atom
• D. Nucleus

Answer: (C)

The identity of an element is defined by the atom—the smallest unit that retains the properties of that element. An atom has a dense nucleus containing protons and neutrons, surrounded by an electron cloud. The number of protons in the nucleus (the atomic number) uniquely specifies which element it is. If you change the number of protons, you get a different element, even if the number of neutrons or electrons stays similar. Molecules are simply groups of atoms bonded together, so they involve more than one atom. Ions are atoms (or groups) that have gained or lost electrons, giving them a charge but not changing the fact that the element is defined by its atom. The nucleus sits at the center and houses the protons and neutrons, but the element’s identity comes from the atom as a whole, not just the nucleus. So, the atom is the basic unit that defines each element.

The identity of an element is defined by the atom—the smallest unit that retains the properties of that element. An atom has a dense nucleus containing protons and neutrons, surrounded by an electron cloud. The number of protons in the nucleus (the atomic number) uniquely specifies which element it is. If you change the number of protons, you get a different element, even if the number of neutrons or electrons stays similar. Molecules are simply groups of atoms bonded together, so they involve more than one atom. Ions are atoms (or groups) that have gained or lost electrons, giving them a charge but not changing the fact that the element is defined by its atom. The nucleus sits at the center and houses the protons and neutrons, but the element’s identity comes from the atom as a whole, not just the nucleus. So, the atom is the basic unit that defines each element.