CHEM104 Midterm: CHEM104 (Midterm ONE)
Document Summary
Substance: pure matter, either an element or a compound. Isotopes have different numbers of neutrons but the same number of protons. They are the atoms of the same element but have different masses. Elements on the steplike ladder are metalloids with the exceptions of aluminum (al), polonium (po) and astatine (at) Remember the five groups (columns) alkali metals (column 1), alkaline earth metals (column 2), Chalcogenes (column 16), halogens (column 17), and noble gases (column 18) H o f br i n cl - the naturally occuring diatomic molecules. Molecular compounds are composed of molecules and almost always contain only nonmetals. Empirical formulas give the lowest whole number ratio of atoms of each element in a compound. Molecular formulas give the exact number of atoms of each element in a compound. Ionic compounds need to remember different possible charges! Inexact numbers depend on how they were determined; all scientific instruments have limits.
