chem -- elements

週期表入面頭20種 elements 有咩係present in the free state on land
I'm not sure about what do you mean by "on land"
Never mind, Let me try,

Hydrogen(H) - 0.000055% of atmosphere is made up of hydrogen in free state

Helium(He) - 0.000524% of atmosphere is made up of helium in free state

Lithium(Li) - All Group I elements readily react with oxygen in air to form oxide, so, there is no free state of lithium

Beryllium(Be) - It react with oxygen to form oxide layer, so, there is no free state of beryllium

Boron(B) - There is no free state of boron

Carbon(C) - Graphite and diamond are free state of carbon which are abundent on Earth

Nitrogen(N) - 78% of atmosphere is made up of nitrogen in free state

Oxygen(O) - 21% of atmosphere is made up of oxygen in free state

Fluorine(F) - It is the strongest oxidizing element, it readily reacts with other elements. So, there is no free state of fluorine

Neon(Ne) - It is a noble gas, and is very unreactive, so, it usually exists free state.

Sodium(Na) - Similar to Li, it is a Grouop I element

Magnesium(Mg) - All Group II elements react with oxygen in air to form oxide, so, there is no free state of them

Aluminium(Al) - It reacts with oxygen in air to form a thin oxide layer, so, there is no free state of aluminium

Silicon(Si) - There is no free state of silicon in natural, silicon forms oxide and silicates.

Phosphorus(P) - It is reactive, so, there is no free state of phosphorus

Sulphur(S) - Free state of sulphpur can be found in region with volcanic activities

Chlorine(Cl) - There is no free state of chlorine

Argon(Ar) - It is a noble gas, and is very unreactive, so, it usually exists free state.

Potassium - Similar to Li and Na, it is a Group I element.
Calcium - Simliar to Be and Mg, it is a Group II element.




黑白灰_唯物主義者_魑魅魍魎

2011-09-04 13:07:02 補充：
Re Se Chan,

Cl2 reacts with water to form a mixture of hypochlorous acid(HClO) and hydrochloric acid(HCl).
Cl2 also reacts with H2 to form hydrogen chloride in sunlight.

2011-09-04 13:07:08 補充：
Besides, Cl2 can combine with a number of metal and non-metal to form chlorides.
So, due to its reactivity, chlorine doesn't exist in the free elemental state in nature.

2011-09-04 13:51:47 補充：
Re 望‵

I'm not sure about this, but I GUESS it will be considered as an ore/mineral/rock.(I don't study geography, I'm not sure about these)

Since aluminium react with oxygen so quickly, it is impossible for you to find a piece of pure aluminium in natural.

2011-09-04 13:51:55 補充：
So, I doubt whether the aluminium inside aluminium oxide layer can be considered as "free state".

Besides, aluminium seldom exist in nature in form of oxide layer covering pure aluminium, instead, it exists as silicates, fluorides, sulphates and crystalline minerals(hydrated oxides).

No free states of chlorine??
It have Cl2!

I'm thinking of Al....
Bauxite is Al2O3
However...
if Al very originally is a free, polished metal...
then protective aluminium oxide layer is cover on it...
is the aluminium under the protective layer consider as free element?