7. What does the mass for each element on the periodic table represent: a. A more accurate mass measurement including more significant figures
b. The regular average mass of all of the ions of that element
C. The weighted average mass of all of the isotopes of that element
d. Those masses include electrons into the mass calculation
NEED THIS ASAP!!

An unknown substance is a white solid at room temperature and has a melting point of 78 °c. which of the following substances is most likely to be the identity of the unknown sample? a. naphthalene, a molecular solid with the formula c10h8 b. silica, a network solid held together by covalent bonds with the formula sio2 c. calcium chloride, an ionic compound with the formula cacl2 d. water, an molecular compound with the formula h2o