Chemistry II Notes

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Chemistry II Notes Ch 2 Atoms and Elements
-88 natural of 112

-elements- matter that cannot be broken down into
simpler substances
-named for planets, mythological
figures, minerals, colors, geographical
locations, and famous people
-named in Latin
or Greek
-1, 2, or 3 letters only the first is
capitalized
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essential elements- required for life C, H, O, N,
Ca, P, K, S, Na, Mg, and Cl
physical properties- those without a
change in the identity of the substance (color,
shape, odor, taste, density, hardness, melting
point, and boiling point) periodic table-
periodic by the properties if the outer shell

Dmitri Mendelev- first periodic table by
mass later Mosely by atomic number
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group- (or family) vertical column of elements
having similar properties
period- horizontal row of elements all in
the same orbital (shell) alkali metals- 1-7 s1
soft shiny, low mp, good conductors

alkaline earth metals- 2-7 s2 shiny, harder, less
active than alkali metals
halogens- 2-7 p5 very active
nonmetals metals- shiny,
malleable, good conductors, high mp, all solids
except Hg
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nonmetals- poor conductors, dull, low mp, low
density
atoms- smallest particle
of an atom that retains the properties of that
element History of the atom
Democritis- (500 BC) all mater is
composed of atoms
John Dalton-
(1908) Atomic Theory 1. All matter is made of
atoms
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2. All atoms of a given element are similar to
each other and different from atoms of other
elements
3. Atoms of two different
elements combine to form compounds
4. A chemical
reaction involves the rearrangement, separation,
or combination of atoms.
5. Atoms
are never created nor destroyed during a chemical
reaction
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Subatomic particles protons- charge, 1AMU, in
nucleus electrons- - charge,
1/2000th AMU, in orbitals neutrons- /- charge,
1 1/2000th AMU, in nucleus Rutherfords
experiment- (1900s) bombarded gold foil with an
alpha source and few particles would bounce back.
If they did it was like shooting a cannon at
tissue paper and not being able to penetrate it
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atomic number- indicates the number of protons or
electrons (if a neutral atom)
mass number- indicates the total of
protons and neutrons (the difference is
neutrons) isotopes- atoms of the same element
with different numbers of neutrons
average atomic mass- weighted (by
abundance) average of all of the naturally
occurring isotopes of that element
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Cl-35 75.5 abundance .755 x 35 26.4 amu
Cl-37 24.5 abundance .245 x 37 9.1 amu
35.5 amu shells-
describes electron behavior by their arrangement
around the nucleus s - spherical single
orbital 2 electrons 1 s p -
dumbbell three orbitals 6 electrons 2 sp
d - double dumbbell 5 orbitals 10 electrons 3
spd f - ? 7 orbitals
14 electrons 4 sp
df
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electron transitions- moving to a higher orbital
absorbs energy (dark line spectrum), moving back
down releases energy (bright line spectrum)

periodic law- the repetition of properties
with increasing atomic number (7 times at
present) Heisenburg uncertainty principle- it
is impossible to determine both the velocity and
location of an electron at the same time
Hunds rule- if
an electron has a choice of equal orbitals it
will enter each one at a time before doubling in
orbitals
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Pauli exclusion principle- two electron that
occupy the same orbital will have opposite spins
.
2 2 6

electron
configuration notation- 1s 2s 2p simplified
electron configuration- from last noble gas

. 2 6

He 2s 2p
orbital notation-
dashes with arrows up is clockwise down
counterclockwise
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Electron dot notation- the elemental symbol
surrounded by the number of outer shell electrons