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The basic unit used to describe the intensity of radioactivity in a sample of material. One curie equals 37 billion disintegrations per second or approximately the amount of radioactivty given off by 1 gram of radium.

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Addition Reaction

A reaction in which two atoms or groups of atoms are added to a molecule, one on each side of a double or triple bond. Types of addition reaction include electrophilic, nucleophilic (polar) and free radical addition (non-polar).

Endothermic

Describes processes that absorb heat energy.

Second Law of Thermodynamics

The universe tends toward a state of greater diorder in spontaneous processes.

Aromatic Hydrocarbons

Benzene and its derivatives.

Atmosphere

A unit of pressure, the pressure that will support a column of mercury 760 mm high at 0 °C.

Zinc

Discovered: known in India and China before 1500 and to the Greeks and Romans before 20 BC as the copper-zinc alloy brass
Origin: The name is derived from the German ‘Zink’.
Atomic no: 30
Mass No: 65
Description: A grey metal with a blue tinge. World production exceeds 7 million tons a year, and it is used to galvanise iron to prevent it rusting. It is also employed in alloys and batteries, and as zinc oxide to stabilise rubber and plastics. Zinc is essential for all living things, and is important for growth and development. The average human body contains about 2.5 grams and takes in about 15 milligrams per day. Some foods have above average levels of zinc, including herring, beef, lamb, sunflower seeds and cheese.

Debye

The unit used to express dipole moments.

Mass Deficiency

The amount of matter that would be converted into energy if an atom were formed from constituent particles.

Features of the Scanning Tunneling Microscope

The scanning tunneling microscope (STM) invented by Heinrich Rohrer and Gerd Binnig in the 1980s still manages to do a great job today and competes with more advanced microscope types.

The scanning tunneling microscope is used for studying the surface atoms that are found on various materials. The device is based on a complex process of "tunneling" electrons between the material and the tip of a probe.

Active Metal

Metal with low ionization energy that loses electrons readily to form cations.