Topic 1 Regents Chemistry Review: Atomic Theory

Matter

Anything that has mass and volume, such as the desk, air, and body, which chemistry studies.

Dalton's Atomic Theory

John Dalton's theory proposing that all elements are composed of indivisible atoms, with atoms of the same element being identical and compounds formed by the combination of atoms of different elements.

Plum Pudding Model

A model of the atom where electrons are embedded in a positively charged sphere, akin to raisins in a pudding, proposed by J.J. Thompson.

Nucleus

The dense central core of an atom discovered by Ernest Rutherford, containing protons and neutrons, with the rest of the atom being mostly empty space.

Atom

Smallest particle of an element

Gold Foil Experiment

Experiment by Rutherford showing a small, dense, positively charged nucleus and mostly empty space in an atom

Rutherford Model

Atom model with a small dense, positive nucleus and mostly empty space

Proton

Positive subatomic particle in the nucleus

Neutron

Neutral subatomic particle in the nucleus

Electron

Negative subatomic particle

Orbital

Region where an electron is likely to be found in an atom

Nucleus

Dense, positively charged core of an atom with protons and neutrons

Valence Shell

Outermost electron shell in an atom

Valence Electron

Electron in the outermost energy level

Atomic Number

Number of protons in an atom, determines its identity

Atomic Mass Unit (amu)

Mass of a proton or neutron

Mass Number

Sum of protons and neutrons in an atom

Bohr Model

Model showing nucleus contents, energy levels, and electrons in an atom

Lewis Structure

Diagram showing valence electrons as dots and shared electrons as lines

Isotope

Atom of an element with a specific number of neutrons

Ground State

State where all electrons are in the lowest energy level

Excited State

State when an electron absorbs energy and moves to higher energy levels

Spectral Lines

Used to identify atoms and molecules