Element Properties: 16-22 atomic number


Atomic symbol: S

Atomic weight: 32.066

Atomic number: 16

Electron configuration: 2-8-6

Oxidation states: +4, +6, -2

State of matter: solid


Discovered in ancient times

Boils at 444.7°C, melts at 112.8°C


Because sulfur is the least reactive non-metal at room temperature, much occurs free in nature. Chemically combined, sulfur is found as sulfide ores, sulfate ores, in petroleum, and in organic matter. Sulfur has three allotropic forms, rhombic sulfur- stable at room temperature, monoclinic sulfur- which is stable between 95.6°C and its melting point, and amorphous sulfur- a plastic rubbery form. All forms slowly revert back to the rhombic form if allowed to stand at room temperature. Its uses are the making of sulfur dioxide, sulfuric acid, matches, black gunpowder, insecticides, and sulfa drugs. Much is used in vulcanizing rubber.


Atomic symbol: Cl

Atomic weight: 35.453

Atomic number: 17

Electron configuration: 2-8-7

Oxidation states: ±1, +5, +7

State of matter: gas


Discovered in 1774 by Carl Wilhelm Scheele

Boils at -35°C, freezes at -101°C


Chlorine is very poisonous and not found free in nature. It is the most abundant halogen, found in seawater, rock salt beds, and human gastric juices. Almost all chlorine comes from the electrolysis of brine or a concentrated solution of salt. Chlorine has a sharp, disagreeable odor, which attacks the skin and mucous membranes of the nose and throat. Much chlorine is used to bleach wood pulp for the paper industry, as well as cotton and linen fabrics. Tap water and swimming pool water and both chlorinated to kill bacteria.


Atomic symbol: Ar

Atomic weight: 39.948

Atomic number: 18

Electron configuration: 2-8-8

Oxidation states: 0

State of matter: gas

Noble Gas

Discovered in 1849 by Lord Rayleigh and Sir William Ramsay

Boils at -185.7°C, melts at -189.2°C


Argon is a colorless, odorless, tasteless monatomic inert gas. It is obtained from the fractional distillation of liquid air. It is used with nitrogen in filling electric light bulbs, and is used with helium as an inert atmosphere in scientific work.


Atomic symbol: K

Atomic weight: 39.0983

Atomic number: 19

Electron configuration: 2-8-8-1

Oxidation states: +2, +4

State of matter: solid

Light metal

Discovered in 1807 by Sir Humphry Davy

Boils at 760°C, melts at 63.3°C


Potassium is a soft, silvery-white alkali metal that is brittle at low temperatures and tarnishes when exposed to air. It is a major essential element for plant growth, and extremely reactive. Potassium is an excellent conductor of heat and electricity. When sufficiently heated, it emits a violet color and bursts into flame when in contact with water. Alloyed with sodium it forms an important heat transfer medium in nuclear power plants.


Atomic symbol: Ca

Atomic weight: 40.078

Atomic number: 20

Electron configuration: 2-8-8-2

Oxidation states: +2

State of matter: solid

Light metal

Discovered in 1808 by Sir Humphry Davy

Boils at 1484°C, melts at 839°C


Calcium is just behind aluminum and iron in the list of abundant metals, and makes up 3% of the earth’s crust. Calcium carbonate can be found as limestone, marble, chalk, seashells, and calcite. It is found as dolomite when combined with magnesium. Calcium is a good reducing agent and forms heavy hydroxide coats when in contact with moist air.


Atomic symbol: Sc

Atomic weight: 44.955910

Atomic number: 21

Electron configuration: 2-8-9-2

Oxidation states: +3

State of matter: solid

Heavy metal, brittle

Discovered in 1879 by Lars Fredrick Nilson

Boils at 2832°C, melts at 1539°C


Scandium is a rare earth metal widely dispersed in nature. It has very few uses, and its low density and high melting point suggest applications as an alloying agent for devices requiring lightweight metals. Scandium emits strong gamma radiation with an 85-day half-life. The chemistry of this element is similar to aluminum and titanium.


Atomic symbol: Ti

Atomic weight: 47.88

Atomic number: 22

Electron configuration: 2-8-10-2

Oxidation states: +2, +3, +4

State of matter: solid

Heavy metal, brittle

Discovered in 1795 by Martain Heinrich Klaproth

Boils at 3260°C, melts at 1675°C


Titanium is a dark gray lustrous metal that constitutes 0.6% of the Earth’s crust. It is very light and strong, and fairly corrosion resistant. Its use as a structural metal is increasing. It is extremely reactive with both oxygen and nitrogen. Its principal uses are as special gears and tools.