ATOMIC THEORY

Atomic Theory

A scientific theory that describes the nature of atoms as the fundamental building blocks of matter.

Solid Sphere Model

The earliest atomic model proposed by John Dalton, suggesting that atoms are tiny, indivisible spheres.

Plum Pudding Model

Proposed by J.J. Thomson, this model depicts atoms as a uniform positive sphere with negative electrons scattered throughout.

Nuclear Model

Developed by Ernest Rutherford, this model introduces a dense atomic nucleus surrounded by orbiting electrons.

Planetary Model

Proposed by Niels Bohr, this model portrays electrons in specific orbits around the nucleus, similar to planets orbiting the sun.

Quantum Model

Based on quantum mechanics, this model describes electrons as existing in a probability cloud around the nucleus, rather than fixed orbits.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Subatomic Particles

Particles that make up an atom, including protons, neutrons, and electrons.

Electron Configuration

The arrangement of electrons in an atom's orbitals, determining its chemical behavior.

Valence Electrons

Electrons in the outermost energy level that determine an atom's chemical properties.

Atomic Nucleus

The positively charged center of an atom, composed of protons and neutrons.

Proton

A positively charged subatomic particle located in the atomic nucleus.

Neutron

A neutral subatomic particle found in the atomic nucleus.

Electron

A negatively charged subatomic particle orbiting the atomic nucleus.

Chemical Reaction

A process that involves the rearrangement of the molecular or ionic structure of a substance.

Energy Levels

The defined layers of energy where electrons reside within an atom.

Atomic Mass

The weighted average mass of an element's isotopes, typically expressed in atomic mass units (amu).

Atom

The smallest unit of an element, consisting of protons, neutrons, and electrons.

Molecule

A group of two or more atoms bonded together, representing the smallest fundamental unit of a chemical compound.

Compound

A substance formed when two or more different elements are chemically bonded together.

Ion

An atom or molecule that has gained or lost one or more electrons, resulting in a net charge.

Covalent Bond

A type of chemical bond formed by the sharing of electron pairs between atoms.

Ionic Bond

A chemical bond formed through the electrostatic attraction between oppositely charged ions.

Chemical Formula

A representation of a substance using symbols for its constituent elements and numbers to denote the ratio of these elements.

Periodicity

The recurring trends that are observed in the properties of elements across different periods of the periodic table.

Atomic Number

The number of protons in the nucleus of an atom, which determines the element's identity.

Mass Number

The total number of protons and neutrons in an atomic nucleus.