[cardrap]

what property is most closely related to the chemical behaviour of an element ? atomic mass or atomic number

thanks

[Mitch]

atomic number

[Corvettaholic]

Atomic number... is it because the farther you go down the table the more violent the reactions? I'm thinking of alkali metals, like going from dropping sodium into water all the way to chucking some cesium in a lake (not that its possible without dying). Okay, I retract my previous statement  

[Donaldson Tan]

If you look at the periodic table, you realize that the elements are arranged in increasing atomic number from left to right, and from top to bottom. Note that elements in the same period are of the same valence shell number and elements in the same group has the same no. of valence electrons (with few exceptions).

Obviously, it would be atomic number. Perhaps atomic mass has a limiting rate fator in virtue being a bulkier reactant.