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Overview Elements are the smallest units of matter that cannot be broken down further by chemical processes. There are 118 known elements, but not all of …

Overview All matter is composed of atoms, the smallest individual units of elements. Each atom is made up of three subatomic particles: protons, …

Overview Electrons are negatively charged subatomic particles that are attracted to an orbit around the positively-charged nucleus of an atom. They reside …

Orbitals are the areas outside of the atomic nucleus where electrons are most likely to reside. They are characterized by different energy levels, shapes, …

Pure substances consist of only one type of matter. A pure substance can be an element or a compound. An element consists of only one type of atom, while …

Molecules have characteristic shapes that are crucial for their function. The arrangement of various electron groups around the central atom dictates …

Life on Earth is carbon-based, as all macromolecules that make up living organisms contain carbon atoms. All organic compounds have a carbon backbone. …

A chemical reaction is a process by which the bonds in the atoms of substances are rearranged to generate new substances. Matter cannot be created or …

Elements have a set number of protons that determines their atomic number (Z). For example, all atoms with eight protons are oxygen; however, the number …

Overview When two atoms share electrons to complete their valence shells they create a covalent bond. An atom’s electronegativity—the force …

Overview When atoms gain or lose electrons to achieve a more stable electron configuration they form ions. Ionic bonds are electrostatic attractions …

Hydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has a …

Atoms and molecules interact with each other through intermolecular forces. These electrostatic forces arise from attractive or repulsive interactions …

Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the …

The potential of hydrogen (pH) is a measure of the acidity or basicity of a water-based solution determined by the concentration of hydronium ions (H3O+). …

A solvent is a substance, most often a liquid, that can dissolve other substances. Here, the substance being dissolved is called a solute. When a solvent …

Oxidation-reduction or redox reactions involve the transfer of electrons from one molecule or atom to another. When an atom gains an electron, another …

Adhesion occurs when one type of molecule is attracted to a different molecule. Water exhibits adhesive properties in the presence of polar surfaces, such …

Cohesion is the attraction between molecules of the same type, such as water molecules. Water molecules have an overall neutral charge but are polar …

The specific heat capacity of a substance refers to the energy required to increase the temperature of one gram of that substance by one degree Celcius. …

The physical form of a substance changes by changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize …