Chemical Context of Life Flashcards

A set of 30 vocabulary flashcards covering fundamental chemical concepts in biology, subatomic particles, chemical bonds, and reactions.

Matter

Anything that takes up space and has mass, which organisms are composed of.

Element

A substance that cannot be broken down to other substances by chemical reactions.

Compound

A substance consisting of two or more different elements combined in a fixed ratio.

Essential Elements

The approximately $25$ elements required by organisms to live, with carbon, hydrogen, oxygen, and nitrogen making up \times 96\text{\textpercent} of living matter.

Trace Elements

Elements required by an organism in only minute quantities.

Atom

The smallest unit of matter that retains an element's properties, composed of neutrons, protons, and electrons.

Atomic Nucleus

The dense center of an atom formed by protons and neutrons, surrounded by an electron cloud.

Atomic Number

The unique number of protons found in the nucleus of an atom for a given element.

Mass Number

The sum of the number of protons and neutrons in an atom's nucleus.

Atomic Mass

The average mass of an element's isotopes, approximated by the mass number but differing slightly due to atomic mass unit definitions.

Isotopes

Atoms of the same element that have the same number of protons but differ in the number of neutrons.

Radioactive Isotopes

Unstable isotopes that decay spontaneously; used biologically in dating fossils, tracing metabolic processes, and medical diagnosis.

Orbital

The three-dimensional space where an electron is found 90\text{\textpercent} of the time.

Valence Shell

The outermost electron shell of an atom.

Valence Electrons

Electrons in the outermost electron shell that determine the chemical behavior and bonding capacity of an atom.

Covalent Bond

A chemical bond formed by the sharing of a pair of valence electrons by two atoms.

Single Covalent Bond

A covalent bond formed by sharing one pair of valence electrons between two atoms.

Double Covalent Bond

A covalent bond formed by sharing two pairs of valence electrons between two atoms.

Structural Formula

A chemical notation showing the bonding arrangement of atoms in a molecule (e.g., H–H).

Molecular Formula

A chemical notation giving the number and type of atoms present in a molecule.

Electronegativity

An atom's attraction for shared electrons in a covalent bond.

Nonpolar Covalent Bond

A type of covalent bond in which electrons are shared equally between two atoms of similar electronegativity.

Polar Covalent Bond

A covalent bond between atoms that differ in electronegativity, causing unequal sharing of electrons and partial charges.

Ionic Bond

A chemical attraction between oppositely charged ions created by the transfer of electrons from one atom to another.

Cations

Positively charged ions.

Anions

Negatively charged ions.

Hydrogen Bond

An attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

Molecular Recognition

Specific binding between biological molecules based on shape complementarity, allowing molecules with similar shapes to produce similar biological effects.

Chemical Reaction

The making and breaking of chemical bonds, converting starting substances (reactants) into ending substances (products), illustrated by photosynthesis: $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$.

Chemical Equilibrium

The state reached when forward and reverse chemical reaction rates are equal, maintaining constant concentrations of reactants and products.