Chapter 9: Electrons in Atoms and the Periodic Table

These flashcards cover key vocabulary and concepts from Chapter 9, focusing on atomic structure, electron configurations, and periodic trends.

Diatomic Element

An element that exists as molecules composed of two atoms, such as hydrogen (H2).

Reactivity

The tendency of an atom to undergo a chemical reaction, which is notably high in Group 1A elements like hydrogen, lithium, and sodium.

Periodic Law

The principle that the properties of elements recur periodically when arranged by increasing atomic number.

Bohr Model

A model of the atom where electrons travel in fixed circular orbits around the nucleus.

Quantum-Mechanical Model

The modern model of the atom which replaces Bohr's orbits with orbitals that represent probability maps of electron locations.

Photon

A particle of light, representing a packet of light energy.

Wavelength

The distance between adjacent wave crests; it determines the color of visible light.

Frequency

The number of wave cycles that pass a stationary point in one second.

Valence Electrons

Electrons in the outermost principal shell of an atom, involved in chemical bonding.

Ionization Energy

The energy required to remove an electron from an atom in the gaseous state.

Emission Spectrum

The set of wavelengths emitted by an atom when its electrons transition to lower energy levels.

Quantum Number

A number that specifies the energy level of an electron in an atom.

Hund’s Rule

Electrons will fill degenerate orbitals singly before pairing up.

Core Electrons

Electrons that are not in the outermost principal shell of an atom.

Metallic Character

The tendency of an atom to lose electrons; decreases across a period and increases down a group.