Inquiry into Life - Chapter 2: The Molecules of Cells

Comprehensive vocabulary flashcards covering atomic structure, isotopes, chemical bonding, properties of water, and acids and bases.

Matter

Anything that takes up space and has mass, existing naturally in solid, liquid, gas, or plasma states.

Element

A substance that cannot be broken down into simpler substances by ordinary chemical means.

Atom

The smallest part of an element that displays the unique chemical properties of that element.

Proton

A positively charged subatomic particle found in the nucleus of an atom, possessing an electric charge of $+1$ and an atomic mass unit (AMU) of $1$.

Neutron

An uncharged subatomic particle located in the nucleus of an atom, possessing an electric charge of $0$ and an atomic mass unit (AMU) of $1$.

Electron

A negatively charged subatomic particle that orbits the nucleus in energy shells, possessing an electric charge of $-1$ and an atomic mass unit (AMU) of $0$.

Atomic number

The number of protons in the nucleus of an atom.

Mass number

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

Periodic table

A tabular arrangement of chemical elements grouped in vertical columns (groups) and horizontal rows (periods) according to recurring physical and chemical characteristics.

Isotopes

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

Radioactive isotope

An unstable isotope that emits various types of energy as radiation while it decays.

Electron shell

An energy level or orbital surrounding the atomic nucleus where electrons are situated.

Octet rule

The principle stating that an atom's outer (valence) shell is most stable when it contains $8$ electrons.

Valence shell

The outermost electron shell of an atom, which determines its chemical reactivity and bonding behavior.

Molecule

A structure formed when two or more atoms bond together chemically (e.g., $O_2$).

Compound

A substance formed when two or more different elements bond together chemically in fixed proportions (e.g., $H_2O$).

Ion

A charged atom or group of atoms created when electrons are completely transferred from one atom to another.

Ionic bond

A chemical bond resulting from the electrostatic attraction between oppositely charged ions.

Covalent bond

A chemical bond formed when atoms share pairs of electrons to complete their valence shells.

Nonpolar covalent bond

A covalent bond in which the sharing of electrons between two atoms is equal or nearly equal.

Polar covalent bond

A covalent bond in which the sharing of electrons between two atoms is unequal, resulting in partial positive and partial negative charges.

Electronegativity

The measure of an atom's attraction for shared electrons in a covalent bond.

Hydrogen bond

A weak attraction between a partially negative atom in one polar molecule and a partially positive hydrogen atom in another polar molecule.

Calorie

The amount of heat energy needed to raise the temperature of $1\,\text{g}$ of water by $1\,^{\circ}\text{C}$.

Heat of vaporization

The amount of heat energy required to convert a liquid into a gas; converting $1\,\text{g}$ of the hottest water to gas requires $540\,\text{calories}$.

Solvent

A liquid substance capable of dissolving other chemical substances to form a uniform solution.

Solute

A dissolved substance contained within a solution.

Hydrophilic

Polar or charged molecules that readily attract and dissolve in water.

Hydrophobic

Nonpolar molecules that do not attract or dissolve in water.

Cohesion

The capacity of water molecules to cling to each other due to hydrogen bonding.

Adhesion

The capacity of water molecules to cling to other polar surfaces.

Surface tension

A measure of the force holding the surface layer of a liquid together, created by cohesive attraction between molecules.

Acid

A substance that dissociates in water to release hydrogen ions ($H^+$), creating a solution with a pH below $7$.

Base

A substance that either releases hydroxide ions ($OH^-$) or takes up hydrogen ions ($H^+$) in water, creating a solution with a pH above $7$.

pH scale

A scale ranging from $0$ to $14$ used to measure the hydrogen ion concentration, indicating the acidity or basicity of a solution.

Buffer

A chemical or combination of chemicals that keeps pH within normal limits by absorbing or releasing excess $H^+$ or $OH^-$ ions.