Chemistry Foundation of Life: Matter, Atoms, and Bonding

Vocabulary flashcards covering key concepts from the lecture notes on matter, atoms, isotopes, and the basics of chemical bonding.

Matter

The substance of which physical objects are made; has mass and occupies space.

Element

A naturally occurring substance with a unique symbol on the periodic table, made of only one type of atom.

Atomic symbol

The letter(s) used to represent an element on the periodic table (e.g., C for carbon, Na for sodium).

Compound

A substance composed of two or more elements in a fixed ratio, with properties different from its elements (e.g., NaCl).

Emergent properties

New characteristics that arise when elements combine to form a compound, not present in the individual elements.

Atom

The basic unit of matter that retains the properties of an element; consists of a nucleus and surrounding electrons.

Nucleus

The center of the atom containing protons and neutrons; positively charged.

Proton

A positively charged subatomic particle located in the nucleus.

Neutron

A neutrally charged subatomic particle located in the nucleus.

Electron

A negatively charged subatomic particle that orbits the nucleus in electron shells or cloud; largely determines chemical behavior.

Atomic number

The number of protons in an atom’s nucleus; defines the element.

Mass number

The total number of protons and neutrons in the nucleus; used to describe isotopes.

Isotope

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

Radioactive isotope

An unstable isotope that decays over time, emitting radiation.

Half-life

The time required for half of a radioactive substance to decay.

Carbon dating

A dating method using carbon-14 decay to estimate the age of organic materials up to about 50,000 years.

Atomic mass unit (amu)

A unit used to express atomic masses, defined as 1/12 the mass of carbon-12.

Electron cloud (quantum model)

A probabilistic region around the nucleus where electrons are likely to be found, not fixed orbits.

Energy level / shell

Discrete levels around the nucleus where electrons reside; electrons can move to higher levels when energized.

Valence

The outermost shell’s electron count or the number of electrons needed to complete that shell; determines bonding behavior.

Valence electrons

Electrons in the outermost shell that participate in bonding.

Octet rule

Most second and third shell electrons are filled to eight to achieve stability.

Noble gas

An element group with complete outer electron shells and typically low reactivity.

Hydrogen

Element with one proton; the first shell holds up to two electrons, giving hydrogen a valence of 1 and high reactivity.

Carbon-12

Most common carbon isotope with 6 protons and 6 neutrons; stable.

Carbon-13

A stable carbon isotope with 6 protons and 7 neutrons.

Carbon-14

A radioactive carbon isotope with 6 protons and 8 neutrons; used in dating.

Cosmogenic carbon-14 production

Carbon-14 is formed in the atmosphere when cosmic rays interact with nitrogen nuclei.