Standard conditions and pure elements

[happyana]

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Does anyone know what the rules are for what constitues a pure element? I get that diatomic elements are pure and should be equal to zero at standard conditions but what are the exceptions? For example, Br2 is a liquid, not a gas, at standard conditions. Are there anymore exceptions?

 

[happyana]

anyone? pllllllllllllllllllllllllleeeassee?

 

[jj2chemastray6]

You're referring to enthalpies of formation, correct?

Its not necessarily diatomic compounds, elements in their standard states is more of a memorized topic. For example, Br2 (l) is bromine in its standard state but so is C (graphite).

Usually standard states are solid metals, monatomic noble gases, or diatomic halogens F2(g), Cl2(g), I2(s). Also O2(g) and Hg(l).

You'll probably be able to figure it out on any question the DAT could throw at you just by the information given. I wouldn't stress on this. My pchem book has a nice table of it so I'm sure you could find one via google if you so choose.