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…

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

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

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

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,…

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…

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…

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

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

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

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

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

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…

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

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

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…

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

Treatment of dyslipidemia patients with lipid-lowering drugs leads to a significant reduction in low-density lipoproteins (LDL) level and a low to…

Cholesterol content of cells must be maintained within the very tight limits, too much or too little cholesterol in a cell results in disruption of…

The nematode C. elegans has emerged as an important model for the study of conserved genetic pathways regulating fat metabolism as it relates to…