Introduction to Atoms, Bonds, and Chemical Reactions

A comprehensive vocabulary review of atomic structure, molecular bonds, chemical interactions, and reactions based on the lecture transcript.

Matter

Anything that has mass and takes up space—solid, liquid, or gas.

Atoms

The smallest functional units of matter.

Molecules

Two or more atoms bonded together.

Element

A pure substance made up of only one kind of atom.

Nucleus

The central part of an atom made up of protons and neutrons, possessing a net positive charge.

Orbital

The region surrounding the nucleus of an atom where the probability is high of finding an electron.

Electron shells

A region around an atom's nucleus where electrons reside.

Energy

The capacity to do work or cause change.

Valence electrons

Electrons located on the outermost shell of an atom.

Atomic Number

The number of protons in an atom.

Atomic mass

Indicates an atom's mass relative to the masses of other atoms, measured in amus.

Mole

The amount of any substance that contains the same number of particles as there are atoms in exactly 12g of carbon.

Isotopes

Atoms of the same element that differ in the number of neutrons they contain.

Molecular formula

A representation of a molecule that consists of the chemical symbols for all of the atoms present and subscripts that indicate how many of those atoms are present.

Compound

A substance composed of two or more different elements.

Covalent bond

A strong chemical bond in which 2 atoms share a pair of electrons.

Structural formula

A type of chemical formula for molecules in which each covalent bond is represented by a line indicating a pair of shared electrons.

Octet rule

The principle that many atoms are most stable when they have eight electrons in their outermost electron shell.

Double Bond

Occurs when atoms share 2 pairs of electrons (four electrons) rather than one pair.

Electronegativity

A measure of an atom's ability to attract electrons in a bond with another atom.

Nonpolar covalent bonds

Covalent bonds between atoms with similar electronegativities (differing by less than 0.4) where electrons are shared fairly equally.

Polar covalent bonds

Bonds in which electrons are shared unevenly because they are closer to the nucleus of the atom with higher electronegativity, creating a difference in electric charge across the molecule.

Hydrogen bonds

Bonds formed when a hydrogen atom in one polar molecule becomes electrically attracted to an electronegative atom (such as oxygen or nitrogen) in another polar molecule.

Enzymes

Molecules that catalyze many biologically important chemical reactions.

Van der Waals dispersion forces

Attractive forces between molecules in close proximity to each other, caused by variations in the dispersion of electron density around individual atoms.

Ion

An atom or molecule that has gained or lost one or more electrons and acquired a net electric charge.

Cation

An ion with a positive net charge.

Anion

An ion with a negative net charge.

Ionic bond

A bond formed between a cation and an anion where electrons are transferred.

Free radical

An atom with a single, unpaired electron in its outer shell that can interact with other molecules to steal an electron.

Chemical reaction

Process that occurs when one or more substances are changed into other substances by the making or breaking of chemical bonds and/or the removal or addition of electrons.