1.vertical columns in the periodic table indicate what information?
a. periods
b. liquids
c. synthetic elements
d. groups and families

2.which of these are families of elements?
a. metals and noble gases
b. shells and nonmetals
c. properties and rare earth elements
d. metalloids and atoms

3.why is the atomic mass of many elements not a whole number?
a. elements are unstable.
b. an element may have isotopes with different numbers of neutrons.
c. the atomic mass includes all the electrons.
d. lsotopes are always expressed in decimals.