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October 18, 2021

Element Properties: 30-38 atomic number

ZINC

Atomic symbol: Zn

Atomic weight: 65.39

Atomic number: 30

Electron configuration: 2-8-18-2

Oxidation states: +2

State of matter: solid

Heavy metal, low melting

Discovered in the 13th century

Boils at 907°C, melts at 419°C

Notes: Zinc is a bluish white lustrous metal, stable in dry air. On exposure to moist air, it becomes covered with a white coating of basic carbonate. It is used extensively in galvanized iron. It is also used as an ingredient in alloys such as bronze, brass, Babbitt metal, German silver, and special alloys for die casting, household utensils, building materials and automotive equipment.

GALLIUM

Atomic symbol: Ga

Atomic weight: 69.723

Atomic number: 31

Electron configuration: 2-8-18-3

Oxidation states: +3

State of matter: solid

Heavy metal, low melting

Discovered in 1875 by Paul-Émile Lecoq de Boisbaudran

Boils at 2403°C, melts at 29.78°C

Notes:

Gallium liquefies just above room temperature. It is silvery white, and soft enough to be cut with a knife. It may take on a bluish tinge due to superficial oxidation. Gallium expands when solidified and super-cools readily, sustaining its liquid form as low as 0°C. It can be used as a coating for optical mirrors, as a liquid seal in a strongly heated apparatus, and as a substitute for mercury in ultraviolet lamps.

GERMANIUM

Atomic symbol: Ge

Atomic weight: 72.64

Atomic number: 32

Electron configuration: 2-8-18-4

Oxidation states: +2, +4

State of matter: solid

Heavy metal, low melting

Discovered in 1886 by Clements Winkler

Boils at 2830°C, melts at 937.4°C

Notes:

Germanium is an important element used in the manufacture of transistors and photocells. Germanium is never found free and is quite brittle, even though the atoms of a germanium crystal are found in the same arrangement as carbon atoms in a diamond. It also reacts quickly with the halogens to form tetrahalides.

ARSENIC

Atomic symbol: As

Atomic weight: 74.92160

Atomic number: 33

Electron configuration: 2-8-18-5

Oxidation states: ±3, +5

State of matter: solid

Non-metal

Discovered in 1649

Melts at 814°C

Notes:

Arsenic is found in both yellow and gray crystalline forms. Gray arsenic is very brittle and tarnishes in the air. It sublimes under high heat. It is often used as a wood preservative, and because if its high toxicity, an herbicide and pesticide.

SELENIUM

Atomic symbol: Se

Atomic weight: 78.96

Atomic number: 34

Electron configuration: 2-8-18-6

Oxidation states: +4, +6, -2

State of matter: solid

Non-metal

Discovered in 1818 by Jöns Jacob Berzelius

Boils at 685°C, melts at 50 or 217°C

Notes:

Selenium exists in many allotropic forms— amorphous, crystalline or red, and gray or metallic. It occurs in both amorphous and gray states, which is why it has two melting points. It is very similar in both chemical and physical properties to sulfur and tellurium. It can convert light directly into electricity and thus makes a good element for solar cells. Selenium can also convert AC power to DC, and therefore makes a good rectifier.

RUBIDIUM

Atomic symbol: Rb

Atomic weight: 85.4678

Atomic number: 37

Electron configuration: 2-8-18-8-1

Oxidation states: +1

State of matter: solid

Light metal

Discovered in 1861 by Robert Bunsen and Gustav Kirchoff

Boils at 688°C, melts at 38.9°C

Notes:

Rubidium is the second most reactive metal—it is lustrous and silver-white in color. It rapidly tarnishes when exposed to air. Rubidium can spontaneously ignite in the presence of air and reacts violently with water.

STRONTIUM

Atomic symbol: Sr

Atomic weight: 87.62

Atomic number: 38

Electron configuration: 2-8-18-8-2

Oxidation states: +2

State of matter: solid

Light metal

Discovered in 1808 by Sir Humphrey Davy

Boils at 1384°C, melts at 769°C

Notes:

Strontium is a silvery white metal that rapidly becomes yellow when exposed to air. To prevent this oxidation, it is stored in kerosene. It is ductile and malleable and can easily conduct current. The heat radioactive strontium emits due to radioactive decay can be used to generate small amounts of electricity. When finely divided, it spontaneously ignites in the presence of air.

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