Oxygen

Oxygen,  ₈O

General properties
Name, symbol	Oxygen, O
Appearance	Colorless (gas) Blueish liquid (liquid)
Oxygen in the periodic table
- ↑ O ↓ S Nitrogen ← Oxygen → Fluorine
Atomic number	8
Standard atomic weight (Ar)
Group, block	, -block
Period	period
Electron configuration
Physical properties
Colorless
Atomic properties

Oxygen is the 8th element on the periodic table and is the second strongest oxidizer, second to fluorine. It has the atomic weight of ~16 (15.9949), but as a gas it is diatomic with a molar mass of ~32.

Properties

Chemical

Oxygen has 6 valence electrons and typically exists with two lone pairs of electrons.

It is highly electronegative, with a 3.44 on the Pauling scale. It reacts directly with almost every element, a major exception being most of the noble metals and gases (except for xenon).

It reacts with many metals to form oxides. These reactions can be slow and gradual (as is the rusting of iron) or extremely fast, as in the combustion of cesium.

Physical

Although in gas form it is indistinguishable from other common gases, in liquid form it is pale blue (and highly reactive). Oxygen is paramagnetic.

Availability

Gaseous oxygen makes up 21% of the atmosphere. For higher concentrations, compressed oxygen can be procured from the companies that sell welding products as well as scuba diving stores. Cryogenic liquid oxygen is harder to get because unlike liquid nitrogen it is a fire and explosive hazard, when it (accidentally) enters in contact with organic materials.

Preparation

Oxygen is extracted from air by fractional distillation on an industrial scale.

In the lab, it can be isolated by:

• electrolysis of water with containing ions
• heating potassium chlorate with manganese dioxide,
• decomposing hydrogen peroxide with manganese dioxide
• Decomposition of hypochlorite solution (laundry bleach) using a small amount of cobalt chloride as a catalyst
• heating potassium permanganate.

A way to make liquid oxygen involves liquifying normal air with liquid nitrogen and collecting the oxygen-rich layer on top.

Handling

Safety

Atmospheric oxygen is not a hazard to health, however at high concentration it becomes dangerous to the lungs and can cause blindness. At concentrations over 50%, it will greatly amplify any exothermic reaction. Liquid oxygen is a fire and explosive hazard when in contact with organic materials and a fire source. It can also cause frostbites if it touches the skin.

Storage

Oxygen tanks and dewars should be kept in dark and cool places, away from any combustible materials. Periodically check the valves for any leaks.

Disposal

Oxygen can be safely released in open air, but never in closed places.

References

Relevant Sciencemadness threads

• LOX (Liquid Oxygen)