Chemistry Basics: Mass, Isotopes, Molecules, Bonds, and Atomic Structure

Vocabulary flashcards covering key concepts from the lecture notes on atomic mass, isotopes, mass vs. weight, Avogadro's number, the mole, elements, bonding, and atomic structure.

Atomic mass

The average mass of an element's atoms, weighted by isotope abundance, measured in atomic mass units (amu); for carbon it is about 12.011.

Isotope

Forms of the same element with different numbers of neutrons, resulting in different atomic masses (e.g., carbon-12 and carbon-14).

Atomic mass unit (amu) / Dalton

A unit equal to 1/12 the mass of carbon-12; roughly the mass of a proton or neutron; historically called a Dalton.

Dalton (older term)

An older name for the atomic mass unit (amu); largely replaced by amu in modern usage.

Avogadro's number

6.022 × 10^23; the number of atoms in one mole of a substance.

Mole

A counting unit representing 6.022 × 10^23 particles; one mole contains that many atoms or molecules of a substance.

Element

A substance consisting of only one kind of atom; cannot be broken into simpler substances by chemical means.

Hydrogen

One of the four most common elements in living organisms; forms water with oxygen and is central to organic chemistry.

Oxygen

A highly abundant element essential for respiration and for forming water with hydrogen.

Carbon

A backbone element of most biological molecules; has an average atomic mass around 12.011 amu.

Nitrogen

An essential element in proteins and nucleic acids; common in amino groups and nucleotide bases.

Calcium

A mineral element important for bones and signaling; needed in small but essential amounts.

Iron (Fe)

A trace mineral element important for oxygen transport in blood and in various enzymes.

Sulfur

A mineral element involved in proteins and in some vitamins; a trace element in biology.

Trace element

Mineral elements required in very small amounts but essential for health.

Calcium (example)

An example of a mineral element needed in small amounts for bones and physiology.

Molecular formula

Notation showing the symbols of the elements in a molecule and their subscripts (e.g., C6H12O6).

Molecule

Two or more atoms bonded together; may or may not be a compound depending on if more than one element is present.

Compound

A substance formed when two or more different elements are chemically bonded (e.g., C6H12O6).

Covalent bond

A bond formed when atoms share electrons to fill their valence shells.

Polar covalent bond

A covalent bond where electrons are shared unequally, creating partial charges.

Nonpolar covalent bond

A covalent bond where electrons are shared equally between atoms.

Hydrogen bond

An intermolecular attraction where a hydrogen atom on one molecule is attracted to an electronegative atom on another molecule.

Ionic bond

A bond formed by electron transfer creating oppositely charged ions that attract each other.

Electron transfer

The process of moving electrons from one atom to another to form ions in ionic bonding.

Nucleus

The dense center of an atom containing protons and neutrons; electrons orbit around it.

Proton

Positively charged subatomic particle in the nucleus; mass ~1 amu.

Neutron

Electrically neutral subatomic particle in the nucleus; mass ~1 amu.

Electron

Negatively charged subatomic particle orbiting the nucleus; very small mass.

Rutherford's gold foil experiment

An experiment showing atoms are mostly empty space with a tiny, dense nucleus; most alpha particles pass through."

Alpha particle

A helium-4 nucleus (two protons and two neutrons) emitted in radioactive processes and used in Rutherford's experiment.

Mass vs Weight

Mass is the amount of matter and is constant; weight is the gravitational force and varies with location (Earth, Moon, Sun).

Valence shell

The outer electron shell of an atom; bonding involves filling or sharing electrons to satisfy this shell.

Electronegativity

A property describing an atom's ability to attract electrons in a covalent bond; influences bond polarity.

Polar molecule

A molecule with an uneven distribution of charge due to polar bonds, resulting in partial charges.