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why aluminium do not react with water under normal conditions?

an element react with oxygen to give a compound with a high melting point. this compound is also soluble in water. the element is likely to be : calcium carbon silicon iron ? whyyyyyyyyyy?
what are amphoteric oxides? how do we identify them?

1. Aluminium does not react with cold water. Aluminum metal rapidly develops a thin layer of aluminum oxide of a few millimeters that prevents the metal from reacting with water. Aluminium reacts readily with steam to give aluminium oxide and hydrogen gas.

 

2. The compound is calcium which reacts with oxygen to give calcium oxide (with high melting point) which dissolved in water to give lime water or calcium hydroxide.

 

3. Amphoteric oxides are those which show both acidic and basic properties.  The only way to identify the amphoteric oxides is by their reaction with acids and bases.

Aluminium and beryllium forms the major amphoteric oxides. Some elements that are able to form amphoteric oxides  are: Be, Si, Ti, V, Fe, Co, Sb, Zn, Ge, Zr, Ag, Sn, Au.

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Aluminum does not react will cool water, because it is not highly active. Here is a link to the metal activity series, which is really helpful in explaining this: http://www.files.chem.vt.edu/RVGS/ACT/no…

 

(Amphoteric oxide) In chemistry, an amphoteric substance is one that can react as either an acid or base.

If you can identify a Lewis acid and a Lewis base on the same molecule, then you may have an amphoteric molecule. Consider zinc oxide (I'll use colons and periods for electrons):
Zn - (O:::)

Zinc has enough electons to fill its 4s and 3d subshells, but not its 4p subshell. A fine Lewis acid, don't you think? Oxygen has three nonbonding pairs, a lovely Lewis base. Amphoteric, yes?


Nitrogen lacks an electron, so it's a Lewis acid, and oxygen has nonbonding pairs to donate, so it's a Lewis base. NO can dimerize though ON-NO to supply the missing electron to nitrogen, so it may not be very acidic.

Nitrous oxide (:N)≡N-(O:::) may also be slightly amphoteric by virtue of the positive charge on nitrogen and the three nonbonding pairs of oxygen, but it isn't really lacking electrons to complete a subshell (or an octet), so it won't be a very good Lewis acid.

Nitrogen dioxide (::O=(N.)-O:::) is one electron short of an octet, and is positively charged to boot, so it should be a fairly spicy Lewis acid. However, the molecule is resonantly stabilized, with the double bond either to the left oxygen or to the right oxygen, and if oxygen donates an electron pair as a Lewis base then NO2 loses its resonance stabilization. That's gonna considerably reduce its basicity, so amphoteric

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