Chapter 2: The Chemical Basis of Life - Atoms, Molecules, and Water

Vocabulary practice flashcards covering atomic structure, chemical bonding, electronegativity, and the physical and chemical properties of water based on Chapter 2.

Atom

The smallest functional unit of matter.

Atomic Nucleus

The central core of an atom that contains protons and neutrons.

Element

A pure substance composed of only one kind of atom.

Isotopes

Chemical elements or atoms of the same element that have a different number of neutrons than protons.

Valence Electrons

Electrons located in the outermost shell of an atom that possess the most energy and are available to combine with other atoms.

Cation

An ion with a net positive charge resulting from the loss of one or more electrons.

Anion

An ion with a net negative charge resulting from the gain of an extra electron.

Atomic Number

The number of protons in the nucleus of an atom, which defines the chemical element.

Atomic Mass

The calculated mass of an element based on the frequency and averages of its naturally occurring isotopes.

Covalent Bond

A chemical bond formed when two atoms share valence electrons.

Octet Rule

The principle stating that atoms react to form stable outer electron shells that are full, which requires 8 electrons for the 2nd and 3rd shells and 2 electrons for hydrogen.

Electronegativity

A measure of an atom's ability to attract shared electrons within a chemical bond.

Polar Covalent Bond

A covalent bond formed when two atoms with differing electronegativities share electrons unequally.

Nonpolar Covalent Bond

A covalent bond in which valence electrons are shared equally between atoms with similar electronegativity values.

Hydrogen Bond

An intermolecular attraction occurring when a hydrogen atom covalently bonded to an electronegative atom in one polar molecule is attracted to an electronegative atom in another polar molecule.

van der Waals Dispersion Forces

Weak intermolecular interactions occurring between nonpolar molecules due to temporary, small differences in electron cloud distribution.

Ionic Bond

A chemical bond formed when a cation binds to an anion through electrostatic attraction following electron transfer.

Hydrophilic

Water-loving substances, such as ions and polar molecules, that interact favorably with and dissolve in water.

Hydrophobic

Water-fearing substances, primarily nonpolar molecules, that do not dissolve in water and tend to group together.

Electronegativity Difference Bond Scale

A classification scale for bond type based on electronegativity difference: nonpolar covalent is $< 0.4$, polar covalent is $0.4$ to $1.8$, and ionic is $> 1.8$.

Biological Functions of Water

Key properties of water including participation in chemical reactions (hydrolysis), plant support, waste elimination in urine, heat dissipation via evaporation, cohesion/adhesion for fluid transport, lubrication in saliva, and surface tension.