Atomic Number Quiz

Atomic Structure and Periodic Table

• Atomic number represents the number of protons present in the nucleus of an atom, which defines the identity of an element.
• The atomic number of an element can be found at the top of each element's box in a periodic table.

Atoms and Isotopes

• When an atom has an unequal number of protons and neutrons, it becomes an ion.
• The number of protons in an atom's nucleus is responsible for giving an atom its most notable characteristics.

Isotopes and Atomic Mass

• The mass number of an atom is defined as the total number of protons and neutrons in the nucleus.
• An isotope of an element is often represented by the symbol of the element followed by a hyphen and the mass number (e.g., C-12).
• The atomic mass of an element on the periodic table represents a weighted average of the masses of its naturally occurring isotopes.
• The term "atomic weight" is often used interchangeably with atomic mass.
• The average atomic mass for an element with multiple isotopes is calculated by taking the sum of the product of the mass of each isotope and its relative abundance.

Isotopes of Elements

• The atomic number (number of protons) remains constant in all isotopes of an element.