Transcript Chapter 3 - Green Local Schools

Atomic Structure & Electron
Configuration
Ch.3
(3-1) Atomic Theory
• All matter is composed of indivisible
particles called atoms
• Certain characteristics shared by all
chemical cmpds
Law of Definite Proportions
• Any sample of a cmpd always has the
same composition (by mass)
– Ex: NaCl always 39% Na & 61% Cl
Law of Conservation of Mass
• Product mass = reactant mass
– Ex: S
sulfur
32.07 amu
+
O2

oxygen
32.00 amu
SO2
sulfur dioxide
64.07 amu
Law of Multiple Proportions
• Mass ratio for combining 1 element w/
another are expressed in small whole
#’s
– Ex: NO2
NO
N2O
Dalton’s Atomic Theory
1. Matter is made of indivisible &
indestructible atoms
2. Atoms of a given element are identical
in their properties
3. Atoms of different elements differ in
their properties
Dalton’s Atomic Theory
4. Atoms of different elements combine
in simple whole-# ratios to form cmpds
5. Chemical rxns consist of the
combination, separation, or
rearrangement of atoms.
Modifications to Dalton’s
Theory
• 2 principles no longer valid
– subatomic particles
– overlooked atoms combining w/ their own
type
Atomic Mass
• p+ + n0 (e- mass negligible)
• Units: atomic mass units (amu)
• Exactly 1/12 the mass of 1 carbon-12
atom
Atomic Mass to Kg
• 1 amu = 1.66 x 10-27 kg
• Mass of copper atom:
63.546 amu x 1.66 x 10-27 kg = 1.06 x 10-25 kg
1 amu
Mole
• (mol): amt of substance
• Avogadro’s constant:
6.02 x 1023 particles
1 mol
• 1 g/mol = 1 amu
Mass & Moles
• Mass of 1 mol of Fluorine atoms:
18.9984 amu x 1.66 x 10-27 kg x 1000 g
1 amu
1 kg
x 6.02 x 1023 = 18.9984 g/mol
1 mol
(3-2) Subatomic Particles
• Smaller particles that make up an atom
• 3 types
Particle
Location
Size
Charge
Electron
(e-)
Outside
nucleus
0.000 549
amu
Negative
Proton
(p+)
Nucleus
1.007
amu
Positive
Neutron
(n0)
Nucleus
1.009
amu
Neutral
Electrodes
• Anode: where e- enter a metal; + charge
• Cathode: where e- leave a metal; charge
Cathode Ray Tube
Experiment
• J.J. Thomson
– e- had mass
– e- had negative charge
Nucleus
• Central region of an atom containing p+
& n0
• Plum-pudding model: Thomson
– e- embedded in positively charged ball of
matter
Gold Foil Experiment
• Ernest Rutherford
• Alpha particles: + charged particles
– dense nucleus w/ lots of empty space
around it
Atomic Number
• # of p+ in the nucleus of an atom
• Mass #: total # of p+ & n0 in the nucleus
• 42He: mass # = 4, atomic # = 2
– 2 p+, 2 n0, 2 e-
Coulomb’s Law
• The closer 2 charges come together,
the greater the force b/w them
• Opposites attract, likes repel
• Strong force: greater than repulsive
force at close distance
– p+ in nucleus
Isotopes
• Atoms of the same element w/ different
#’s of n0
– Ex: Helium-3 (1n, 2p), Helium-4 (2n, 2p)
• Radioisotope: unstable atom that
undergoes radioactive decay
(3-3) Electromagnetic
Spectrum
• Total range of electromagnetic radiation
– e- have properties of both particles &
waves
Wavelength
• λ: distance b/w 2 consecutive peaks or
troughs
–m
Frequency
• v : # of waves that pass a stationary pt.
in 1 sec.
– Hz
Speed of Light
• c = 3.0 x 108 m/s
• Speed of light = freq. x wavelength
c
= v
λ
– Ex: v = _c_ = 3.0 x 108 m/s
λ
7.6 x 10-7 m
= 3.9 x 1014 /s = 3.9 x 1014 Hz
Line-emission Spectrum
• Distinct lines of colored light produced
by excited atoms of an element passing
through a prism
Quantum Theory
• Tells exact E of the e-, but only the
probability that the e- is in a particular
region
– Quantized
Quantum #’s
•
•
•
•
Principal (n): 1-7, E level e- is located
Shape: sublevel w/in E level
Orientation: orbital w/in sublevel
Spin: +1/2, -1/2
Bohr’s Atomic Model
• Describes e- in terms of their E states
– Ground state: lowest E state
– Excited state: higher E state than ground
Orbitals
• Regions
Don’t
forget: of space where you can expect
- of specific E
to
find
e
an orbital is the shape of the
space
where there
a Don’t
high forget:d, f
• s (sphere),
p is
(dumb-bell),
an orbital is the shape of the
probability of finding electrons
space where there is a high
probability of finding electrons
The s orbitals are spheres
This is the shape of p orbitals
The “1s” orbital is a
sphere, centered
around the nucleus
The 2s electrons have a
higher energy than the 1s
electrons. Therefore, the 2s
electrons are generally more
distant from the nucleus,
making the 2s orbital larger
than the 1s orbital.
z
The three 2p orbitals,
2px, 2py, 2pz
y
x
so 3s electrons are
generally found
further from the
nucleus than 1s,
2s, or 2p electrons
Pauli Exclusion Principle
• No more than 2 e- can occupy a single
orbital & must have different spins
Electron Configuration
• Description of occupied e- orbitals in an
atom
• s (1 orbital), p (3), d (5), f (7)
s
s
• F:
p
d
1s22s22p5
• Main E level, orbital, # of e-
f
Orbital Diagrams
• Similar to e- config. but lines designate
orbitals and arrows designate e– __ __
1s 2s
__ __ __
2p
http://www.colorado.edu/physics/2000/applets/a2.html
Aufbau Principle
• Lowest & most stable E levels filled first
– 4s before 3d
Hund’s Rule
• Orbitals are occupied by 1 e- before any
pairing occurs
Noble Gas Configuration
• Electron Config.: S: 1s22s22p63s23p4
• Noble Gas Config.: S: [Ne]3s23p4
• Unless specified do not use noble gas
configuration!!!!