unit 2 chem flashcards

Electron

A negatively charged subatomic particle.

Radioactivity

The spontaneous decay or disintegration of the nucleus of an atom.

Nucleus

The dense center of an atom with a positive charge.

Proton

A positively charged subatomic particle.

Neutron

An electrically neutral subatomic particle.

Isotopes

Atoms with the same number of protons but different numbers of neutrons.

Atomic number (Z)

The number of protons in a nucleus.

Mass number (A)

The total number of protons and neutrons in a nucleus.

Radioisotope

An isotope that emits radioactive gamma rays and/or subatomic particles.

Photoelectric effect

Electrons are emitted by matter that absorbs energy from shortwave electromagnetic radiation.

Quantum

A unit or packet of energy.

Photon

A unit of light energy.

Rutherford's gold foil experiment

An experiment that proved atoms have a small, dense, positively charged nucleus.

Bohr model

Proposed that electrons are found in specific circular paths or orbits around the nucleus.

Quantum mechanics

The application of quantum theory to explain the properties of matter.

Orbital

The region around the nucleus where an electron has a high probability of being found.

Heisenberg’s Uncertainty Principle

The idea that it is impossible to know the exact position and speed of an electron at a given time.

Wave function

The mathematical probability of finding an electron in a certain region of space.

Electron probability density

The probability of finding an electron at a given location, derived from wave equations.

Aufbau principle

The principle that electrons occupy the orbitals of lowest energy first.

Pauli Exclusion Principle

An atomic orbital may describe at most two electrons with opposite spins.

Hund’s Rule

Electrons occupy orbitals of the same energy to maximize unpaired electrons.

Quantum numbers

Numbers that describe the quantum mechanical properties of orbitals.

Shell

An atom's main energy level, indicated by the principal quantum number.

Subshells

Orbitals of different shapes and energies as determined by the secondary quantum number.

Covalent bond

A chemical bond in which atoms share the bonding electrons.

Electronegativity

The ability of an atom in a molecule to attract shared electrons to itself.

Dipole

A separation of positive and negative charges in a region in space.

Hydrogen bond

Attractive forces in which hydrogen covalently bonded to an electronegative atom is also weakly bonded to another electronegative atom.

Network solids

Solids in which all the atoms are covalently bonded to each other.

Amorphous solid

A solid that lacks an ordered internal structure.

Ionic bond

The electrostatic attraction between oppositely charged ions.

Valence electrons

Electrons in the outermost principal quantum level of an atom.

Lewis Structure

A diagram that represents the arrangement of covalent electrons and bonds in a molecule.