Which period has elements where all of the atoms have valence electrons in the 2nd energy level?

in theory, limestone is composed principally of the compound calcium carbonate - caco3, but in reality this compound is deposited in conditions involving a number of other compounds as impurities so it ends up being a mixture of many compounds.

hope this : -)

tony (lordcaos066)

false

because it does not have the potential to be entirely used up

its first and third is your answer i did the qustion the fourth isnt right

a corroding iron, if that's one of your choices