Transcript Atomic Calculations CPS Chemistry

Atomic Calculations
CPS Chemistry
Parts of the atom…
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Electron
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Negative Charge
Allows atoms to bond & react
9.1x10-31kg
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Neutron
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Neutral Charge, number can vary in nucleus
Binds nucleus together
1.7x10-27kg
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Proton
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Positive Charge
unique number, gives atoms/element their
identity 1.7x10-27kg
Atomic Number
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A unique number which is equal to the
number of protons in the nucleus (whole
number) of an element
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Examples
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Hydrogen – 1
Lithium – 3
Oxygen - 8
Isotopes
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Isotopes are when there are varying
numbers of neutrons in the nucleus for a
type of element
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Example for hydrogen
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Protium – 1Proton, 0 Neutrons
Deuterium – 1Proton, 1 Neutron
Tritium – 1 Proton, 2 Neutrons
Nuclide – a general term for any isotope of
an element
Atomic Mass
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The atomic mass is the sum of the masses
of the protons and neutrons in the nucleus
of a atom – electrons are not counted
because their relative mass is insignificant
compared to the other two subatomic
particles.
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The atomic mass is usually expressed as a
decimal because it is an average of the
masses of all the isotopes for that element
How many neutrons?
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If the atomic number is the number of
protons in an element, and the atomic
mass (round to the nearest whole
number) is the number of protons +
neutrons than to find the number of
neutrons…
Atomic Mass – Atomic Number = # of Neutrons
Example
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If the atomic number for silver (Ag) is 47,
and the atomic mass is 108, how many
neutrons are there?
Atomic # = 47
Atomic Mass = 108
108-47 = 61 neutrons
How many electrons are there?
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In a neutral atom, the number of electrons
equals the number of protons
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If there is a +1 next to an atom, it means
that it has one less electron than protons
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If there is a -1 next to an atom, it means
that it has one more electron than
protons
Example 2
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Find the number of subatomic particles
associated with Sn+2
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On the periodic table of elements Tin has
an atomic number of 50, and an atomic
mass of 119 
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Number of protons = 50
Number of neutrons = 69
Number of electrons = 48
Calculating Atomic Mass of Molecules
When you add the atomic mass of two
particles together, you get the atomic
mass of the molecule.
 You can have more than one of any atom,
so you need to multiply the mass times
that number.
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Ex. CO is Carbon Monoxide
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Carbon has an atomic mass of 12
Oxygen has a mass of 16
The total mass for the molecule is
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12+16= 28g
What about More than One of an atom?
If there are more than one atom of a
given kind, multiply that subscript number
by the atoms mass.
 Then add the total of all the atoms.
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Examples:
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H2O Multiply the hydrogen by 2 then add it
to the oxygen.
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(Hx2)+O=
(1x2)+16=18g
C6H12O6
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(Cx6)+(Hx12)+(Ox6)=
(12x6)+(1x12)+(16x6) =180g
The Mole:
more than just a furry little creature…
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It is a unit of
measure, since atoms
are very, very, very
small a better way to
count atoms so the
unit is the mole
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The mole is equal to 6.022x1023 also
called Avogadro’s number
1 mole of a element = atomic mass
of that element
Grams to moles
Take the given number of grams and
multiply it by 1 mole over the atomic mass.
Example: How many moles is contained in a
72g sample of magnesium?
72 g of Mg x 1 mol = 3 mol
24 g
Moles to grams
Take the given number of grams and
multiply it by atomic mass over 1 mole
Example: How many grams are there in a
1.5 mole sample of sulfur?
1.5 mol x 32 g = 48 grams
1 mol
Atoms to moles & moles to atoms
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To calculate the number of moles in a
amount of atoms, divide by Avogadro's
number
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To calculate the number of atoms in a
sample, first convert to moles, then
multiply by Avogadro's number
Island of Instability…
There are 92 naturally occurring elements
But scientists can make elements in the lab, the
current “prize” is to make & stabilize element 114…