Glossary
Atom
The fundamental building block of matter, incredibly tiny, and composed of subatomic particles.
Example:
A single atom of gold is the smallest unit that retains the chemical properties of gold.
Atomic Mass
The mass of one atom of an element, typically expressed in atomic mass units (amu), and numerically equivalent to the molar mass in g/mol.
Example:
The atomic mass of chlorine is about 35.45 amu, which means its molar mass is 35.45 g/mol.
Atomic Number
The number of protons in the nucleus of an atom, which uniquely identifies an element.
Example:
Every atom of carbon has an atomic number of 6, meaning it always has 6 protons.
Avogadro's Number
The number of particles (atoms, molecules, ions, etc.) in one mole of a substance, equal to 6.022 x 10²³.
Example:
One mole of any gas, like helium, contains 6.022 x 10²³ Avogadro's number of helium atoms.
Dimensional Analysis
A powerful problem-solving technique that uses conversion factors to systematically convert between different units by canceling out unwanted units.
Example:
To convert 50 grams of CO₂ to moles, you would use dimensional analysis with the molar mass of CO₂ as your conversion factor.
Electrons
Negatively charged subatomic particles that orbit the nucleus of an atom in specific energy levels or orbitals.
Example:
Chemical bonds are formed when electrons are shared or transferred between atoms.
Molar Mass
The mass in grams of one mole of a substance, numerically equal to the atomic mass for elements or the sum of atomic masses for compounds.
Example:
The molar mass of oxygen gas (O₂) is approximately 32.00 g/mol, meaning 32.00 grams of O₂ contains one mole of O₂ molecules.
Mole
A unit of measurement in chemistry representing a specific number of particles (6.022 x 10²³), acting as a bridge between the microscopic and macroscopic worlds.
Example:
If you have 18.02 grams of water, you have exactly one mole of water molecules.
Neutrons
Neutral (no charge) subatomic particles located in the nucleus of an atom.
Example:
Isotopes of an element have the same number of protons but differ in the number of neutrons, affecting their atomic mass.
Nucleus
The small, dense, positively charged core of an atom, containing protons and neutrons.
Example:
Almost all of an atom's mass is concentrated in its nucleus.
Protons
Positively charged subatomic particles found within the nucleus of an atom.
Example:
The number of protons in an atom's nucleus determines its atomic number and thus its identity as an element, like 6 protons for carbon.