Biology I - Chapter 2

Vocabulary practice flashcards covering fundamental chemical concepts from Campbell Biology Chapter 2, including atomic structure, isotopes, electron configuration, chemical bonds, and chemical reactions.

Matter

Anything that takes up space and has mass.

Element

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

Compound

A substance consisting of two or more elements in a fixed ratio, possessing emergent properties distinct from its constituent elements.

Essential Elements

Chemical elements required by an organism to live and reproduce, accounting for approximately $20\text{--}25$% of the $92$ naturally occurring elements.

Trace Elements

Elements required by an organism in only minute quantities, such as iron in all organisms or iodine in vertebrates.

Atom

The smallest unit of matter that still retains the properties of an element.

Subatomic Particles

The structural constituents of an atom, consisting of protons (positively charged), electrons (negatively charged), and neutrons (electrically neutral).

Atomic Nucleus

The dense core at the center of an atom, composed of tightly packed protons and neutrons.

Dalton

A unit of mass used for subatomic particles, atoms, and molecules, where one proton or neutron has a mass close to $1\,\text{dalton}$ ($1.7 \times 10^{-24}\,g$).

Atomic Number

The unique number of protons in the nucleus of an atom of a specific element.

Mass Number

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

Atomic Mass

The total mass of an atom, which can be closely approximated by its mass number.

Isotopes

Two or more atoms of the same element that have the same number of protons but differ in their number of neutrons.

Radioactive Isotope

An unstable isotope whose nucleus decays spontaneously, emitting particles and energy and transforming into another element.

Potential Energy

The energy that matter stores because of its location or spatial structure.

Electron Shell

An energy level representing a specific state of potential energy for electrons located at fixed distances from an atomic nucleus.

Valence Electrons

Electrons located in the outermost electron shell of an atom, which dictate the atom's chemical behavior and reactivity.

Valence Shell

The outermost electron shell of an atom containing the valence electrons.

Inert Atom

An atom with a completely filled valence shell, rendering it chemically nonreactive.

Orbital

The three-dimensional space in which an electron is located $90\%$ of the time.

Chemical Bond

An attraction that holds atoms close together, formed when atoms share or transfer valence electrons.

Covalent Bond

A strong chemical bond formed when two atoms share one or more pairs of valence electrons.

Single Covalent Bond

A covalent bond resulting from the sharing of one pair of valence electrons between two atoms.

Double Covalent Bond

A covalent bond resulting from the sharing of two pairs of valence electrons between two atoms.

Molecule

Two or more atoms held together by covalent bonds.

Valence

The bonding capacity of an atom, typically equal to the number of unpaired electrons in its outermost shell.

Electronegativity

The attraction or pulling power of a particular atom for shared electrons within a covalent bond.

Nonpolar Covalent Bond

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

Polar Covalent Bond

A covalent bond between atoms that differ significantly in electronegativity, pulling shared electrons closer to the more electronegative atom and producing regions of partial positive ($\delta^+$) and negative ($\delta^-$) charge.

Ion

An atom or molecule that has acquired a net electrical charge due to the gain or loss of one or more valence electrons.

Cation

A positively charged ion formed when an atom loses electrons.

Anion

A negatively charged ion formed when an atom gains electrons.

Ionic Bond

A chemical bond formed by the electrostatic attraction between oppositely charged ions (a cation and an anion).

Ionic Compound (Salt)

A compound formed by ionic bonds, structured as a crystal lattice rather than discrete individual molecules.

Hydrogen Bond

A weak chemical interaction formed when a hydrogen atom covalently bonded to one electronegative atom is attracted to another electronegative atom.

Van der Waals Interactions

Fleeting, weak attractions between molecules or atoms caused by temporary, asymmetric distributions of electron density.

Reactants

The starting substances in a chemical reaction that undergo chemical rearrangement.

Products

The final substances produced as a result of a chemical reaction.

Chemical Equilibrium

The state of a reversible reaction in which the rate of the forward reaction equals the rate of the reverse reaction, stabilizing the concentrations of reactants and products.