Which is a polyatomic ion?
a. o2–
b. mg2+
c. nh4+
d. na+

One of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description?

Can someone me with these questions plz.

Which statement is true about this reaction? 14n+1h 15o it is a practical source of energy on earth. it occurs only outside the solar system. its product is heavier than each of its reactants. it shows the critical mass of an element.