Unit 4: The Atom

These flashcards cover key concepts and definitions related to atomic theory, structure, and characteristics.

Evolution of the Atom

The historical progression of ideas regarding atomic structure from early philosophical concepts to modern atomic theory.

Dalton's Atomic Theory

A set of postulates that describe atoms as indivisible particles that rearrange during chemical reactions but are neither created nor destroyed.

Law of Conservation of Mass

In a chemical reaction, the total mass of reactants is equal to the total mass of products; mass is neither created nor destroyed.

Thomson's Discovery

In 1897, Thomson discovered the electron, a negatively charged particle that exists within an atom.

Plum Pudding Model

Thomson's atomic model that proposed atoms are a mixture of positively charged matter with negatively charged electrons embedded within.

Rutherford's Atomic Model

Rutherford proposed a new model featuring a nucleus containing protons, with electrons in an electron cloud surrounding it.

Chadwick's Discovery

In 1930, Chadwick discovered the neutron, a particle with no electric charge that, alongside protons, makes up the atomic nucleus.

Atomic Number (Z)

The number of protons in an atom's nucleus, determining the chemical element.

Mass Number (A)

The total number of protons and neutrons in an atom's nucleus.

Isotopes

Atoms of the same element that have the same atomic number but different mass numbers due to varying numbers of neutrons.

Ions

Atoms that have gained or lost electrons and thus carry a charge; anions have gained electrons and cations have lost electrons.