Chemical Context of Life - Vocabulary

Vocabulary flashcards reviewing fundamental chemical concepts, atomic structure, bonding, and molecular properties based on OpenStax Biology readings.

Matter

Any substance that occupies space and has mass.

Elements

Unique forms of matter with specific chemical and physical properties that cannot break down into smaller substances by ordinary chemical reactions.

Atom

The smallest unit of matter that retains all of an element's chemical properties.

Nucleus

The central region of an atom containing protons and neutrons.

Proton

A positively charged subatomic particle located in the nucleus of an atom with a mass of approximately $1\,amu$ ($1.67 \times 10^{-24}\,g$).

Neutron

An uncharged subatomic particle located in the nucleus of an atom with a mass of approximately $1\,amu$ ($1.67 \times 10^{-24}\,g$).

Electron

A negatively charged subatomic particle orbiting the nucleus with a mass of approximately $9.11 \times 10^{-28}\,g$ (about $\frac{1}{1800}\,amu$).

Atomic Number

The characteristic number of protons in an atom, used to distinguish one element from another.

Mass Number

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

Atomic Mass

The calculated mean of the mass numbers for an element's naturally occurring isotopes.

Isotopes

Different forms of the same element that have the same number of protons but a different number of neutrons.

Radioisotopes

Unstable isotopes that emit neutrons, protons, and electrons to attain a more stable atomic configuration.

Half-Life

The time required for half of the original concentration of an isotope to decay back to its more stable form.

Periodic Table

A system created by Dmitri Mendeleev in 1869 that organizes elements by atomic number and groups them based on shared chemical and physical properties.

Chemical Reactivity

The ability of elements to combine and chemically bond with each other.

Molecule

A chemical structure consisting of two or more atoms chemically bonded together.

Bohr Model

An early model of the atom developed by Niels Bohr in 1913 depicting a central nucleus surrounded by electrons in circular orbitals at specific energy levels.

Octet Rule

The principle stating that, with the exception of the innermost shell, atoms are most energetically stable when they have eight electrons in their valence shell.

Valence Shell

The outermost electron shell of an atom.

Inert Gases

Group 18 elements (helium, neon, and argon) that have filled valence shells and are highly stable and unreactive as single atoms; also called noble gases.

Electron Orbitals

Three-dimensional spaces around the nucleus where electrons are most likely to be located, classified as s, p, d, and f subshells.

Reactants

The starting substances consumed in a chemical reaction, usually found on the left side of a chemical equation.

Products

The substances created by a chemical reaction, usually found on the right side of a chemical equation.

Balanced Chemical Equation

A chemical equation in which the number of atoms for each element is equal on both sides, adhering to the law of conservation of matter.

Compound

A substance formed from molecules containing atoms of more than one type of element.

Homonuclear Molecule

A molecule consisting of two or more bonded atoms of the same element, such as molecular oxygen ($O_2$).

Reversible Reactions

Chemical reactions that can proceed in either direction depending on the relative concentrations of reactants and products.

Equilibrium

A state in reversible reactions where a relative balance between reactants and products is achieved.

Cations

Positively charged ions formed when an atom loses one or more electrons.

Anions

Negatively charged ions formed when an atom gains one or more electrons, designated with an "-ide" suffix.

Ionic Bond

A chemical bond formed between ions of opposite charges as a result of electron transfer.

Electrolytes

Ions (such as sodium, potassium, and calcium) necessary for nerve impulse conduction, muscle contractions, and water balance.

Covalent Bond

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

Polar Covalent Bond

A covalent bond in which electrons are shared unequally, resulting in partial positive ($\delta+$) and partial negative ($\delta-$) charges.

Nonpolar Covalent Bond

A covalent bond formed between atoms of the same element or elements with similar electronegativity that share electrons equally.

Hydrogen Bond

A weak interaction between a slightly positive hydrogen atom in a polar molecule and a slightly negative atom in another molecule.

Van der Waals Interactions

Weak attractions between molecules caused by slight fluctuations in electron density when molecules are in close proximity.

Carbon Dating

A method of radiometric dating that measures the decay ratio of carbon-14 ($^{14}C$) to calculate the age of formerly living remains under $50000\text{ years}$ old.