Download CHEMISTRY unit 2

UNIT 2: THE PERIODIC TABLE
I. The Atomic Theory
1) GREEK THEORY
ALL matter is made of 4 “elements”:
Earth
Air
Fire
Water
B) DEMOCRITUS
 460-360BC
 Matter is made of indivisible particles (atoms)
C) JOHN DALTON (1808)
 Elements are made of atoms.
 All atoms of element are identical.
 Atoms of a given element are different from those of
any other element.
 Atoms combine with other atoms to form compounds.
 Atoms are not created not destroyed in a chem
reaction.
D) J.J. THOMSON (around 1910)
 Proposed that the atom might be something like plum
pudding  (a pudding with raisins randomly
distributed throughout)
E) ERNEST RUTHERFORD (1911)
 Gold foil experiment…
 Alpha particles deflected by something in air…this
puzzled him…designed exp that directed the alpha
particles to metal foil….foil is surrounded by detector
coated with substance that flashed when hit by
particles…results were different than he thought…most
particles passed thru foil, some deflected at high
angles and others reflected backwards….
 If plum pudding model was correct, the huge alpha
particles would crash thru foil like cannonballs thru
paper…the large deflection could only be charged by
center of concentration of positive charge
 SO….he concluded that the nucleus must be positive to
balance the negative charge
 1919: Rutherford concluded that nucleus of atom
contained protons. His co-worker Chadwick showed
there were neutrons in the nucleus in (1932).
F) NIELS BOHR
 Electron moves around nucleus in various energy
levels, in circular orbits
 Niels Bohr postponed his wedding and canceled his
honeymoon in order to complete his theory of the
atomic model.
G) QUANTUM/WAVE MECHANICAL
MODEL
 E- s are in orbitals
 1926 Ernest Schrodinger
II. Subatomic particles
Proton
Positive
1.6725 x 10 -27 kg
Electron
Negative
9.1 x 10 -31 kg
Neutron
Neutral
1.6748 x 10 -27 kg
III. The Nucleus
a) Central core of atom, positive, contains all of atoms
mass there
b) Atomic # = # of protons
= # of electrons, IF neutral atom
c) Atomic mass= sum of protons and neutrons
c) Atomic mass
 MOLE=unit of measurement for telling # of atoms and
molecules
 Huge relationship
 1 mole of substance = atomic mass = 6.02 x 10 23 atoms
(or molecules)
Huge huge huge huge huge huge huge huge huge huge
d) Isotope
 Atoms of same element with the same # of protons but
a different # of neutrons
IV. E- cloud
a) Electron = negative
b) Electron cloud: space in which e-s are likely to be
-whirling around nucleus, in energy levels w/in
cloud
c) Energy levels= orbitals
Energy levels
Orbital
How many total e-?
Subshells/sub-orbitals
K
2
s=2
L
8
s=2, p=6
M
18
s=2, p=6, d=10
N
32
s=2, p=6,d=10, f=14
c)Valence
 # of electrons in outermost shell
 Determine chemical properties
d) Quark
 Particles that make up the other subatomic particles
V. THE PERIODIC TABLE
 A) Dmitri Mendeleev: 1869-published the table of the
elements…today it’s called the PERIODIC TABLE
 groups elements according to properties
 “periodic”: repeating at regular intervals
B) columns: vertical
 Groups
 Families
 Valence #
c) period-horizontal rows
d) Elemental key
 Mass, # atoms, #electrons, #neutrons, #protons,
valence e-#
 ALSO:
RADIOACTIVE: greater than or equal to atomic # 82
SYNTHETIC: greater than atomic # 92, also called
transuranic element
E) METALS
 Good conductor of heat and electricity
 Shiny
 Malleable
 Ductile
 3 or less valence electrons
 WHERE?
F) NONMETALS
 Poor conductor of heat and electricity
 Dull
 Non-malleable
 Non-ductile
 5 or more valence electrons
 WHERE?
G) METALLOIDS
 Characteristics of both metals and nonmetals
 WHERE?
H) PERIODIC PROPERTIES
1) Atomic size decreases as you move from left to right
across a period.
Atomic size increases as you move down a period.
 2) ionization energy: energy needed to remove a
valence electron
**This decreases as you move down a family.
**It increases as you move across a family.
3) Electron affininty
 “attracting ability”
This increases as you move down a pd.
This decreases as atomic size increases.
Note:
 EA =EN ???
 Electron affinity: the energy change when a neutral
atom attracts an electron to become a negative
ion. Electronegativity: the ability of an atom in a
molecule to draw bonding electrons to itself.
HUGE
VI. FORCES
 1) electromagnetic force: can either attract or repel
particles on which it is acting
*e-s stay in cloud bc of this
2) Strong force: opposes EM force between protons.
Glues protons together to form nucleus
3) Weak force: key to power of sun, resp for radioactive
decay
4) gravity: weakest
VII. IONS
a) ion: charged particle
b) Cation: positively charged particle
c) Anion: negatively charged particle
d) Diatomic molecules: certain atoms can not appear
alone….these are called diatomic molecules
**Learning tool: BrINClHOF