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CHAPTER 2
CONCURRENT ENROLLMENT
CHEMISTRY
ATOMS
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ELECTRONS
 Thomson found a charge to mass ratio of an
electron to be -1.76 x 108 C/g
 Millikan’s oil drop experiment determined the
electron mass to be 9.11 x 10-31 kg
RADIATION
 Becquerel discovered radioactivity
Three type of radiation
 Gamma (γ) rays are high-energy “light”
 Beta (β) rays are high-speed electrons
 Alpha (α) rays are a 2+ charged He nucleus
COMPONENTS
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Rutherford’s gold foil experiment
 Atoms have a nucleus
 Atoms are made up mostly of space
 Protons exist in the nucleus with a + charge
Electrons mass is 9.11 x 10-31 kg, the charge is Protons mass is 1.66 x 10-27 kg, the charge is +
Neutrons mass is 1.67 x 10-27 kg, there is no charge
AMU means 1.66053 x 10-27 kg, so a proton and neutron are 1
AMU each
Atoms are small
 Diameters between 1 x 10-10m to 5 x 10-10m, Ǻ = 1 x 10-10 m
so it is 1A to 5A
Isotopes have the same number of protons but different number
of neutrons
COMPOUNDS AND ELEMENTS
Compounds are made up of elements and the
number of each element
 H2O
 Atomic weights are an average of all the
isotopes for that element
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 Atomic weight = (% isotope#1)(mass)+(% isotope#2)(mass)
100
MOLES
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An amount of a substance, similar to dozen.
One dozen eggs would not weigh the same as one
dozen horses, the same is true in atoms
One mole of anything is 6.02 x 1023 particles of that
substance. This is known as Avogadro’s number
If you times magnesium atoms mass to this number,
you will get 24.3 g per one mole. This is the atomic
mass of magnesium.
CHEMICAL FORMULAS
All compounds have constant ratios. This
means that the number of elements in a
compound remain constant
 One mole of water would then contain, two
moles of hydrogen and one mole of oxygen
 One molecule of water would contain, two
atoms of hydrogen and one atom of oxygen
 Because of this law you can find mass
percentage of any element in any given
compound
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