(((exam))). very thzx10000000000000
1)an element is a pure substance which cannot be broken down into anything simpler by chemical methods
2)An atom is the smallest part of an element which has the properties of that element
3)isotopes are different atoms of the same element ,with the same number of protons but different numbers of neutrons
更新1:
chinese meaning...thz=]=]
更新2:
thz a lot`=]=]i will ask ga^^