chem

Element

A pure substance that cannot be broken down.

Compound

Made by chemically combining two or more different atoms.

Mixture

Made by physically mixing two or more substances; can be separated.

Proton

Positively charged particle found in the nucleus with a mass of 1.

Neutron

Neutral particle found in the nucleus with a mass of 1.

Electron

Negatively charged particle with the smallest mass, located in electron shells.

Isotopes

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

Mass Number

The total number of neutrons and protons in an atom.

Protons

Identified by the atomic number of an element.

Electrons

In neutral atoms, the number equals the number of protons.

Neutrons

Calculated as mass number minus protons.

Isotopic Symbols

Represent the mass number on top and atomic number on the bottom.

Electron shells

Arrangement of electrons around the nucleus, based on energy levels.

Valence Electrons

Electrons that determine the chemical properties of an element and are related to its group in the periodic table.

Ion

An atom with an uneven number of protons and electrons.

Cation

A positively charged ion formed when metals lose electrons.

Anion

A negatively charged ion formed when non-metals gain electrons.

Ionic Compound

Formed when an anion and a cation are attracted due to electrostatic forces.

Physical Change

A change in state or appearance without forming a new substance.

Chemical Change

A process where new substances are formed through breaking and forming chemical bonds.

Reactants

Starting substances in a chemical reaction found on the left side of the equation.

Products

New substances formed in a reaction found on the right side of the equation.

(s)

Indicates a solid state in a chemical equation.

(l)

Indicates a liquid state in a chemical equation.

(g)

Indicates a gaseous state in a chemical equation.

(aq)

Indicates an aqueous solution in a chemical equation.

Balancing Chemical Equation

Ensuring the number of atoms for each element is the same on both sides.

Law of Conservation of Mass

States that mass cannot be created or destroyed in a chemical reaction.

Mass of Reactants

Must equal the total mass of the products in a chemical reaction.

Chemical Bonding

Involves attraction between atoms that results in the formation of compounds.

Electrostatic Force

The force that attracts anions and cations to form ionic compounds.

Energy Levels

The fixed energies an electron can have within an atom.

Atom

The smallest unit of matter that retains the properties of an element.

Nucleus

The central part of an atom containing protons and neutrons.

Shell Model

Describes the arrangement of electrons in an atom's electron shells.

Valence Shell

The outermost shell of an atom that contains valence electrons.

Stability

A condition achieved when an atom's valence shell is full or empty.

Oxidation

The process of losing electrons during a chemical reaction.

Reduction

The process of gaining electrons during a chemical reaction.

Homogeneous Mixture

A mixture that has a uniform composition throughout.

Heterogeneous Mixture

A mixture that consists of visibly different substances or phases.

Exothermic Reaction

A chemical reaction that releases energy in the form of heat.

Endothermic Reaction

A chemical reaction that absorbs energy from its surroundings.

Catalyst

A substance that increases the rate of a chemical reaction without being consumed.

Activation Energy

The minimum energy required for a chemical reaction to occur.

Synthesis Reaction

A reaction where two or more substances combine to form a new compound.

Decomposition Reaction

A reaction where a compound breaks down into simpler substances.

Single Replacement Reaction

A reaction where one element replaces another element in a compound.

Double Replacement Reaction

A reaction involving the exchange of ions between two compounds.

Combustion Reaction

A reaction that occurs when a substance combines with oxygen and releases energy.