Chapter 2: The Chemical Context of Life — Vocabulary Flashcards

Vocabulary flashcards covering key concepts from the lecture notes on chemical foundations of biology (matter, elements, bonds, isotopes, and molecular interactions).

Matter

Anything that takes up space and has mass; composed of elements.

Element

Substance that cannot be broken down into simpler substances by chemical reactions.

Compound

Substance consisting of two or more elements in a fixed ratio with properties different from its elements.

Essential element

Element required for normal growth, development, and health of organisms (about 25 of the 92 natural elements).

Major elements in living matter

The four most abundant elements (carbon, hydrogen, oxygen, nitrogen) that make up about 96% of living matter.

Trace element

Element required in minute quantities by an organism.

Atomic number

Number of protons (and electrons in a neutral atom).

Mass number

Sum of protons and neutrons in the nucleus; approximate atomic mass.

Isotope

Atoms of the same element that have the same number of protons but different numbers of neutrons.

Radioactive isotope

Isotope that is unstable and decays, releasing particles and energy.

Neutron

Subatomic particle with no electrical charge; mass ~1 Dalton.

Proton

Positively charged subatomic particle; mass ~1 Dalton.

Electron

Negatively charged subatomic particle; orbits the nucleus; very small mass.

Nucleus

Central core of the atom containing protons and neutrons.

Electron shell

Region around the nucleus where electrons are likely to be found; each shell has a characteristic distance and energy.

Valence electron

Electron in the outermost shell; largely determines chemical behavior.

Valence shell

Outermost electron shell.

Orbital

Three-dimensional space where an electron is likely to be found; each shell contains orbitals.

Covalent bond

Bond formed by sharing a pair of valence electrons between atoms.

Molecule

Two or more atoms held together by covalent bonds.

Single bond

Sharing of one pair of valence electrons.

Double bond

Sharing of two pairs of valence electrons.

Ionic bond

Bond formed by transfer of electrons; attraction between oppositely charged ions (cation and anion).

Ion

Charged atom or molecule due to gaining or losing electrons.

Cation

Positively charged ion.

Anion

Negatively charged ion.

Ionic compound (salt)

Compound formed by ionic bonds; often forms crystals (e.g., NaCl).

Electronegativity

Atom’s attraction for electrons in a covalent bond; affects polarity.

Polar covalent bond

Covalent bond with unequal sharing of electrons, producing partial charges.

Nonpolar covalent bond

Covalent bond with equal sharing of electrons.

Hydrogen bond

Weak attraction between a hydrogen atom bonded to an electronegative atom and another electronegative atom.

Van der Waals interactions

Weak attractions due to transient dipoles; can be collectively strong.

Molecular shape

Three-dimensional arrangement of a molecule’s atoms; critical for function.

Hybridization

Mixing of atomic orbitals (s and p) to form hybrid orbitals with specific geometry.

Molecular recognition

Biological interactions depend on molecular shape; similar shapes can have similar effects.

Molecular model

Visual representations (space-filling or ball-and-stick) used to illustrate molecules.