3. Distinguish between a complex substance and an elemental substance.
A1, A2a
4. (a) What are the two general classes of ele
ments? (b) Do all elements fit definitely int
one of these classes? A1, A2e
5. Distinguish between a compound and
mixture. A1, A2, A5a
6. What are the five most abundant element
by mass in the earth's surface environment
A3d
7.) (a) What are the properties of metals? (b)
nonmetals? A2e​