Review for Unit 3 Test: The Atom

Comprehensive vocabulary flashcards covering subatomic particles, atomic structure, isotopes, electromagnetic radiation, atomic models, and emission spectra for the Unit 3 Test.

Proton

A positively charged subatomic particle with a relative mass of approximately $1\,\text{amu}$ located in the nucleus; the number of protons determines the elemental identity.

Neutron

A subatomic particle with zero electrical charge and a relative mass of approximately $1\,\text{amu}$, located inside the nucleus of an atom.

Electron

A negatively charged subatomic particle with a relative mass of approximately $0\,\text{amu}$ (about $\frac{1}{1836}$ of a proton), occupying the space in the electron cloud outside the nucleus.

Neutral atom

An atom that possesses an equal number of positively charged protons and negatively charged electrons, resulting in no net electrical charge.

Atomic number

The number of protons in an atom's nucleus, which defines the identity of an element and determines its position on the modern periodic table.

Mass number

The total number of protons and neutrons contained in an atom's nucleus ($\text{Mass number} = \text{protons} + \text{neutrons}$).

Isotopes

Atoms of the same element that contain the same number of protons but different numbers of neutrons, resulting in different mass numbers.

Average atomic mass

The weighted average mass of all naturally occurring isotopes of an element, calculated using each isotope's mass and percent abundance.

Photon

A basic particle and discrete packet (quantum) of electromagnetic radiation that has no mass, no electrical charge, and travels at the speed of light in a vacuum.

Electromagnetic spectrum

The complete range of electromagnetic radiation ordered by frequency, wavelength, or energy, including radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma rays.

Bohr model

An atomic model proposing that electrons orbit a dense, positively charged nucleus only in specific, fixed circular paths (shells) with discrete, quantized energy levels.

Energy level

A fixed shell at a specific distance from the nucleus where an electron can reside with a distinct amount of energy without radiating energy.

Ground state

The normal, lowest-energy orbital state of an atom's electrons before the absorption of external energy.

Excited state

An unstable, higher-energy state that an electron transitions to after absorbing external thermal, electrical, or radiant energy.

Flame test

An analytical technique where heating an element excites its electrons, causing them to emit characteristic colors of light as they return to lower energy levels, aiding in elemental identification.

Emission spectrum

A distinctive pattern of bright colored lines against a dark background, produced when excited electrons release photons at specific wavelengths corresponding to energy-level differences.

Dalton's atomic model

The original atomic model developed by John Dalton describing the atom as a tiny, solid, hard, indivisible, and indestructible sphere.

Nuclear model

The atomic model developed following the gold foil experiment that introduced a central, dense nucleus surrounded by an electron cloud.