Oxygen

OXYGENthe element is very commonhighly reactive nonmetallic elementmajor component of airthe second largest single component of the earth's atmosphere (21% by volume)Oxygen is the most abundant element by mass in the Earth‘s crust as part of oxide compounds such as silicon dioxide.the atmosphere of Mars contains only about 0.15% oxygen usually bound with other elementsproduced by plants during photosynthesis necessary for aerobic respiration

Properties• Name: Oxygen • Symbol: O • Atomic number: 8 • Atomic weight:

15.9994 • Group number: 16 • Period number: 2

IntroductionPhase gasMelting point -218.79C

Boiling point -182.96C

• freshwater contains about 6.04 milliliters (mL) of oxygen per liter• Oxygen has vital biological role

•6 CO2 + 6 H2O + photons → C6H12O6 + 6 O2

•C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + 2880 kJ·mol−1

Propertiesheavier than air

soluble in water

without smell or taste

the gas is colourless, odourless and tasteless

chemical bonds with almost all other elements

three isotopes

Propertyliquid O2 and solid O2 have a light blue color

highly paramagnetic

Electronegative

highly oxidizing

releasing heat

Liquid oxygen

Propertiesthe shell structure of oxygen

History

• Discovered by: Joseph Priestley, Carl Scheele

• Discovered at: England, Sweden

• Discovered when: 1774

Joseph Priestley

Preparation• large number of different methods for its

preparation

1) Preparation of oxygen using potassium chlorate

2 KClO3 ==> 2 KCl + 3 O2

2) Preparation of oxygen using hydrogen peroxide

2 H2O2 ==> 2 H2O + O2

Preparation3) Preparation of oxygen by electrolysis of

water 2 H2O ==> 2 H2 + O2

4) Preparation of oxygen by the decomposition of salts

2 KNO3 ==> 2 KNO2 + O2

5) Preparation of oxygen from air by

distillation

Compounds

• oxygen is very reactive

• oxygen forms chemical bonds with almost all other elements

• oxygen derivatives are prone to form free radicals

• the most common oxidation numbers are -1,-2

CompoundsHydroxide Aluminium hydroxide, Al(OH)3 Barium hydroxide, Ba(OH)2

Oxide Carbon dioxide, CO2

Water has the chemical formula H2O

Alcohols (R-OH) methanol, CH3OH

Methanol burns in air forming carbon dioxide and water:2CH3OH + 3 O2 → 2CO2 + 4H2O

Ozone

allotropic form of oxygen

important component of the atmosphere

effect on the ozone layer

ozone is toxic!

used for drinking water treatment

Applications

oxygen is essential to respiration used in medicine used in welding and cutting (3,500 °C) making of steel and methanol Smelting process A notable application of O2 as a low-

pressure breathing gas is in modern space suits and in diving.

Applications

• Oxygen cutting

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