Answers (2)
This is simple arithmetic if you have a periodic table. You do have a printed periodic table, right? You can get the information at www.chemicalelements.com/index.html but you really need your own printed copy to carry with you. It will be a primary reference for everything you do.
There is a diagonal line, B-C, Si-P, Ge-As, Sb-Te, and Po-At. Elements to the left of the line are metals, meaning they lose an electron easily, elements to the right of the line are non-metals, and elements on the line are semiconductors.
C - 12.011
Cl2 - 2 x 35.4527 = 70.9054
F2 - 2 x 18.9984032 = 37.9968064
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120.913 We can drop the rest because the figure for carbon only has three decimals. This is the mass in grams of 6.023 x 10^23 molecules of the given substance.
(5.56 x 10^-3 g)/120.913g x 6.023 x 10^23 = 2.769584743 x 10^19 molcules