Just this little portion of Chemistry right here. I'm just curious.?

I've been taking Chemistry almost like every semester in College. from General to Organic, I'm just so curious about how scientists or Chemists determine the amount of atoms in their respective compound.

for example: MNO2 or Magnesium dioxide? (correct me if i'm wrong)

At the given molecular formula above, Oxygen has 2 atoms..Now, how on earth can a scientist or a chemist can determine the number of each element in a compound. Of course you cannot see an atom in a mixture because it's very very small and i think even a microscope can't do it. Is this found on a periodic table? i only see their atomic number, mass and electronegativity but not their number when they're mixed with other elements..please explain

2 Answers

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  • 8 years ago
    Favorite Answer

    mass ratios and volume ratios at first. Then mole ratios.

    http://www.kentchemistry.com/links/bonding/empiric...

  • Matt
    Lv 5
    8 years ago

    Using modern techniques, mass spectrometry strips an electron from each molecule, giving them one positive charge each, and flings them through a magnetic field. The magnetic field bends the molecule's path, and the lower the mass to charge ratio, the more it bends. Molecules that didn't pick up a positive charge fly straight through and are ignored. We can see where the molecules hit the target, and the amount it bent tells us the mass to charge ratio very precisely. We know the charge is equal to one electron per molecule, so multiplying by that gives us the molecular weight.

    http://en.wikipedia.org/wiki/Mass_spectrometry

    From the molecular weight, we can use atomic weights to figure out the number of each atom in the molecule. The discoveries that enabled us to do this, such as the law of definite proportions, the law of multiple proportions, and the hypothesis that each atom of an element weighs the same (wrong, but close enough for the time), came about in the 19th century. These were based on observations of gases reacting in simple whole-number ratios.

    http://www.factmonster.com/ce6/sci/A0856765.html

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