Download Unit One: Atomic Theory/Configuration

Atomic Theory
• History of the Theory:
– Early ideas of the atom
• Democritus
• Aristotle
• John Dalton (pg. 56)
Atomic Theory
• History of the Theory:
– Early ideas of the atom
• Democritus - “atomos”; atoms exist
• Aristotle - atoms do NOT exist
• John Dalton (pg. 56)
Atomic Theory
• History of the Theory:
– Early ideas of the atom
• Democritus - “atomos”; atoms exist
• Aristotle - atoms do NOT exist
• John Dalton (pg. 56) - 2000 years later; atoms
exist
–
–
–
–
Matter is made up of atoms.
Atoms are indivisible.
Atoms of different elements are different.
LAW OF CONSERVATION OF MATTER
More Recent Atomic Theory
•JJ Thomson
• E. Rutherford
Electrons in cathode ray
experiment
Nucleus in gold foil
experiment
Modern Atomic Theory
• Neils Bohr
•Schrodinger
Energy levels
Sublevels & orbitals
Subatomic Particles
Particle
Location
Charge
Actual Mass
Relative
Mass
Proton
Nucleus
+1
1.673x10-24
1
Neutron
Nucleus
None
1.675x10-24
1
Electron
Electron
Cloud (in
energy
levels)
-1
9.11x10-28
1
1840
Proton Significance
• Gives the atom its identity
• Equivalent to the atomic number
• Massive particle so adds to the atom’s
mass
• Gives the nucleus its positive charge
• Balances the negative charge of the
electrons
Neutron Significance
• Neutron glue that holds the nucleus
together
• Massive particle so adds to the atom’s
mass (mass number= p + n)
• Number can differ from one atom to
another giving isotopes
Electron Significance
• Responsible for chemical properties
• Forms ions when gained or lost, which
leads to a charge
Atomic Number
The picture is NOT
completely correct.
• Atomic # IS the
number of protons in
the atom. It is NOT
always the number of
electrons.
•Therefore, the atomic
# gives the atom its
identity...its name.
Atomic Number
• In isotopic notation, the atomic number
is shown in the lower left corner of the
element symbol.
• Example:
6C
Atomic NumberQuick Check
• If an atom is found to have 28 protons,
what is its identity?
• What is the atomic number of
phosphorus?
• How many protons does barium have?
• Show the following elements in “isotopic
notation”:
– Lithium, sodium, sulfur, lead
Charge
• Charge = oxidation state
– Oxidation state is just a fancier way to say it.
• A charged atom results from an inequality
between protons and electrons in an atom.
• Which of those particles (protons or
electrons) are more likely to be gained or lost
from an atom? Why?
Charge
• Example: Calcium has 20 protons. It
often loses electrons to other atoms. If
calcium loses 2 electrons, the atom will
have only 18 electrons. What will the
charge be?
– Answer: +2 charge
Charge
• In symbolic notation, the charge is listed
in the top right corner of the element
symbol. If the charge is neutral, then
the corner is left blank.
– Example: Cl-1 means a chlorine atom with
17 protons and 18 electrons. (It has one
extra negative charge.)
Charge
Quick Check
• What is the charge of sulfur when it
gains 2 electrons to the neutral atom?
• Write the symbolic notation to represent
an atom of aluminum that has lost 3
electrons leaving 13 protons and 10
electrons.
• How many protons and electrons are in
the following atom? Cu 2+
Mass Number
• Consider the subatomic particles.
Which TWO particles have enough
mass to matter?
• Mass number is always a whole
number...no decimals.
• Mass number is calculated by adding
the number of protons to the number
of neutrons.
Mass Number
• In symbolic notation, the mass number
is shown in the upper left corner of the
element symbol.
• Example:
12 C
6
Mass Number
Quick Check
• If a sodium atom has 11 protons and 12
neutrons, what is the atom’s mass
number?
• How many neutrons does a copper
atom with a mass number of 64 have?
• How many protons and neutrons are in
the atom represented with this symbolic
notation: 3216S
Isotopic Notation Summary
• Shorthand way to record the element symbol,
atomic number, charge, and mass number.
• With this information, you can deduce the
number of protons, neutrons, and electrons in
the atom being represented.
Mass #
Atomic #
X
Charge
Blocks on the Table
• PROTONS give an atom its identity. They
are the ONLY subatomic particle that must be
identical from one atom to another. Neutrons
AND electrons can vary...
• SO, how can we create ONE box on the
periodic table to represent ALL atoms of an
element? We must represent AVERAGE
atoms. (That’s why the atomic mass has
decimals.)
Atomic Mass
• Atomic mass = the weighted average of
all of the types of atoms of the element
– Must know the % abundance and the mass
number
– Check out the example!
Atomic Mass Example
• Copper exists as a mixture of 2 types of
atoms. The lighter copper has 29
protons and 34 neutrons, and it makes
up 69.17% of all copper atoms. The
heavier type has 29 protons and 36
neutrons. It makes up the remaining
30.83% of copper on earth. What is the
atomic mass of copper?
Atomic Mass Calculation
• Chlorine has two isotopes. Chlorine-35
has an exact weight 34.968852 amu,
and it has a 75.77% abundance. The
other isotope has 36.965903 amu.
What is the atomic mass?
TIME
OUT!
Isotopes
• The three carbon atoms are ISOTOPES of carbon.
– Definition: atoms of the same element that have
different numbers of neutrons
– Application: Does the difference of electrons
matter when considering ISOTOPES?
• Since neutrons are massive, a change in the
number of neutrons gives a different mass number.
– Mass number = protons + neutrons
• “Sisters” - all with the same # of protons but slightly
different masses
IF ALL THE ATOMS OF
CARBON ARE NOT
IDENTICAL, WHAT’S THE
STORY WITH THE CARBON
BLOCK ON THE PERIODIC
TABLE? WHICH ONE DOES IT
REPRESENT?
Isotope/Atomic Mass Lab
• Try it yourself now!
– Get your sample of Candium.
– Draw the data table on your notebook
paper.
– Gather the data, and calculate the atomic
mass of candium.
– You can eat your sample when you’re
done! 8-)
Energetic Electron
• Electrons are energetic, and they exist on
energy levels.
• Quantum: specific amount of energy needed
to move from one energy level to the next;
energy levels are given principal quantum
numbers as a result
• During this movement, energy is absorbed
and released.
• Light is sometimes visible when the energy is
released.
Quantum Illustration
Quantum =
distance between
two energy levels
Principal Quantum
Number (n) =
begin counting
closest to the
nucleus
Quantum Leap Illustration
1. An electron from n=2
(ground state) can
absorb a quantum of
energy and jump to
n=3 (excited state).
2. Excited state is
temporary.
3. The electron will soon
release the quantum
and fall back to ground
state.
4. The released energy
will travel in a wave.
Electromagnetic Spectrum
(All energy waves fall into one of these
categories.)
Calculating the
Emission of Energy
• Two Equations to calculate the energy:
1. Speed of light = wavelength x frequency
c = λν
c = 3.0 x108 m/s (speed of light is constant)
2. Energy = Planck’s constant x frequency
E = hν
h=6.626x10-34 Jsec (Planck’s constant)
Finding a Connection
Look at the two equations. What variable
do they have in common?
A.) Speed of light (c)
B.) Wavelength (lambda)
C.) Frequency (nu)
D.) Energy (E)
Electromagnetic Wave
Calculations
• So, if I know the _______ of a wave,
then I can calculate its wavelength AND
its energy.
Energy Practice Problem:
If the wavelength is 0.001 meters, then
what is the frequency of the wave?
A.) 300,000 Hz
B.) 3.0x1011 Hz
C.) 3.33x10-12 Hz
D.) 6.626x10-37 Hz
Energy Practice Problem:
If the wavelength is 0.001 meters, then
what is the energy of the wave?
A.) 1.99x10-22 J
B.) 2.21x10-45 J
C.) 1.99x1046 J
D.) 6.626x10-37 J
Energy Practice Problem:
If the frequency is 7.0x1013 Hz, what is
the wavelength of the wave? What is
the energy of the wave?
A.) 4.29x106 m; 4.63x1020 J
B.) 2.33x105 m; 1.55x10-28 J
C.) 4.29x10-6 m; 4.63x10-20 J
D.) None of these
Periodic Table Labeling
S block: blue
d block: red
P block: yellow
f block: green
Hotel Tarvin
• Managers:
– Aufbau: Each room/bed on the lower floors must
be occupied before moving to a higher floor.
– Pauli: A maximum of two guests may occupy a
bed. Guests must sleep head to foot.
– Hund: Single guests must occupy separate beds
in a room. No pairing occurs unless no empty
beds exist.
Hotel Tarvin
Rooms available:
S: Single room, has only one bed (sleeps 2)
P: Prestige room, has three beds (sleeps 6)
D: Deluxe room, has five beds (sleeps 10)
F: Fabulous room, has 7 beds (sleeps 14)
The analogy...
• Hotel = electron cloud
• Floors = energy levels
– 1-7 COEFFICIENTS
• Rooms = sublevels (shapes)
– s = sphere, p = dumbbell, d & f
• Beds = orbitals ( & axis)
– x, y,and z
• Guests = electrons
– Up and down = direction of spin
Let’s practice...
• Write the electron configuration for:
–
–
–
–
–
Fluorine
Magnesium
Bromine
Palladium
Xenon
• Write the noble gas notation for the elements
above.
What does this all mean?
• Let’s analyze the configuration of
magnesium.
–
–
–
–
Energy levels
Sublevels
Electrons
Valence level and electrons
• What can I NOT find represented in the
electron configuration?
– Orbitals
– Pairing
Orbital Diagrams
• Visual representation of electron cloud
• Shows everything that electron configuration
shows PLUS orbitals & pairing
– How to Draw an Orbital Diagram
• Write the electron configuration first.
• Draw the “beds” (orbitals) under each room.
• Put the electrons in the “beds.”
– Let’s practice with the electron configurations
written already.
Analyzing Orbital Diagrams
& Stability of Atoms
• Electrons are responsible for the chemical
properties (personalities) of atoms.
– STABLE = All orbitals (beds) are full.
– PRETTY STABLE = All orbitals (beds) are full
OR half-full.
– UNSTABLE = Empty orbitals (beds) exist.
NOTE: If an atom has to have an empty orbital, it is
best for the empty orbital to be on the valence energy
level so that it might be filled by electrons from a
nearby atom.
Analyzing Stability
Draw the orbital diagram of sodium.
Is sodium stable, pretty stable, or
unstable?
A.) Stable
B.) Pretty Stable
C.) Unstable
Analyzing Stability
Draw the orbital diagram of chromium.
Is Cr stable, pretty stable, or unstable?
A.) Stable
B.) Pretty Stable
C.) Unstable
Practice Analyzing Stability
1. Draw the orbital diagram of sodium. Is
sodium stable, pretty stable, or
unstable?
– Answer: UNSTABLE; Sodium has one half-full
orbital, but it’s third energy level has three empty p
orbitals.
2. Draw the orbital diagram of chromium.
Is Cr stable, pretty stable, or unstable?
–
Answer: UNSTABLE; chromium has one empty
orbital.
Exceptions to the Rules
• Exceptions to Aufbau principle:
– Chromium and Copper columns ONLY
– Stability of filled and half-filled sublevels
• Arrangement’s impact on bonding
Atomic Emission Spectra
•
•
•
•
Unique to each element
“Fingerprint”
Used to identify unknowns
Shows all wavelengths of visible light
given off by an atom
• Flame Test Lab