Molecules Gallery

James Clerk Maxwell, caricature

James Clerk Maxwell (1831-1879). Caricature of the Scottish physicist James Clerk Maxwell. Maxwell's works cover a wide area of science, and he is regarded as one of the finest minds of the 19th century. His major work was on light and electromagnetic waves. He showed that oscillating charges produced waves in an electromagnetic field, and that these waves had the same velocity as light. This led him to predict other forms of electromagnetic radiation, such as radio waves. His equations introduced the value c for the speed of light. He also worked on the motions of molecules in a gas, and showed that Saturn's rings must be composed of numerous particles

© GARY BROWN/SCIENCE PHOTO LIBRARY

Isotretinoin anti-acne drug

Isotretinoin anti-acne drug, molecular model. Atoms are represented as tubes and are colour- coded; carbon (yellow), hydrogen (white) and oxygen (red). Isotretinoin, also known as roaccutane, belongs to a group of drugs derived from vitamin A, called retinoids. It acts by reducing the amount of sebum (oil) that sebaceous glands in the skin produce. Excessive production of sebum blocks the sebaceous glands and creates an ideal environment for the bacteria that cause acne. Isotretinoin is only used when other treatments, such as antibiotics, have failed. This is because of its many side effects, which include birth defects, kidney disease and possibly depression

© DR TIM EVANS/SCIENCE PHOTO LIBRARY

Ionic bonding in sodium chloride, artwork C017/7242

Ionic bonding in sodium chloride. Computer artwork showing the formation (top) of sodium chloride (common salt) and a model of the cubic crystal lattice (bottom) created by this chemical reaction. This is a classic case of ionic bonding, a type of chemical bond formed through an electrostatic attraction between two oppositely charged ions. Ionic bonds are formed due to the attraction between an atom that has lost one or more electron (known as a cation) and an atom that has gained one or more electrons (known as an anion). In the formation of sodium chloride, the sodium atom (top left) lost one electron, which is captured by the chlorine atom (top right). In the cubic crystal lattice, sodium ions (Na+) are represented by yellow spheres and chlorine ions

© CARLOS CLARIVAN/SCIENCE PHOTO LIBRARY