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~400 BC
DEMOCRITUS VS. ARISTOTLE
•Came up with the
word atom “atomos”
•Said matter was
made of atoms
•Said matter was
uniform throughout,
NOT made of atoms
•People believed
him, even though he
was wrong!
~1800 AD
JOHN DALTON
MODERN ATOMIC THEORY
•Atoms can not be created, divided, or destroyed.
•Elements have their own unique atoms.
•Atoms of elements combine to make new
compounds.
~1900 AD
JJ THOMSON
PLUM PUDDING MODEL
•Atom was mostly empty space.
•Pudding was positive field and raisins were
negative particles (called corpuscles).
•Corpuscles made up most of the weight of the
atom.
~1909
ERNEST RUTHERFORD
DISCOVERED NUCLEUS
•Center of atom was called nucleus.
•Nucleus made up most of the weight of the atom.
•Electrons were negative particles that randomly
orbited the nucleus.
~1912
NIELS BOHR
ELECTRON ORBITALS
•Electrons orbited the nucleus on 7 different
energy levels.
•Electrons furthest away from the nucleus had
the most energy.
~1926
ELECTRON CLOUD MODEL
•Designed by a group of scientists.
•Electron cloud is 10,000 times larger than the
nucleus, but is still mostly empty.
•Electrons are in the cloud but can not be
pinpointed at an exact time because they move
so quickly.
DMITRI MENDELEEV---1860
•First periodic table based on atomic mass
•Was able to predict where missing elements would be filled
in later
HENRY MOSELEY---1914
•Rearranged elements according to atomic number
•Current table we use today, with elements filled in as they are
discovered or created
6
C
Carbon
12.0
ISOTOPES of an element have the same
number of protons and electrons, but a
different number of neutrons.
5
B
Boron
10.8
GROUPS (18)
P
E
R
I
O
D
S
(7)
METAL, NON-METAL, OR METALLOID
•Also called semi-conductors
•Brittle and dull as a solid
•Can be dull OR shiny
•Ductile
•Good conductor of heat and electricity
•Left side of periodic table
•Malleable
•Mostly gases
•Mostly solids
•Not ductile or malleable
•Poor conductor of heat and electricity
•Right side of periodic table
•Shiny
•Stair step of periodic table
• Non-metals
• Metalloids
• Metals
•
•
•
•
Alkali metals
Alkaline earth metals
Halogen
Hydrogen
• Inner transitions
• Noble gases
• Transition elements
Alkali Metals:
Li, Na, K, Rb,
Cs, Fr
Alkaline Earth Metals:
Be, Mg, Ca, Sr, Ba, Ra
Ti, Fe, Ni, Cu,
Ag, Au, Cd,
Hg, U
Boron Group: B, Al, Ga, In, Tl
Carbon Group: C, Si, Ge, Sn, Pb
Nitrogen Group: N, P, As, Sb, Bi
Oxygen Group: O, S, Se, Te, Po
Halogens: F, Cl, Br, I, At
Noble Gases: He, Ne, Ar, Kr, Xe, Rn
H