PropertieProperties of s of
AtomsAtoms
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SC3 Students will use the modern atomic theory to explain the characteristics of atoms.
a. Discriminate between the relative size, charge, and position of protons, neutrons, and electrons in the atom.
b. Use the orbital configuration of neutral atoms to explain its effect on the atom’s chemical properties.
c. Explain the relationship of the proton number to the element’s identity.
d. Explain the relationship of isotopes to the relative abundance of atoms of a particular element.
e. Relate light emission and the movement of electrons to element identification.
Atomic Structure Goals
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Matter
SubstanceMixture
ElementCompound
This will be our FOCUS
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What is an What is an Element?Element?•One of the ~116 known One of the ~116 known
“Pure”, un-cutable “Pure”, un-cutable substances….substances….that still retain that still retain the properties of that substance.the properties of that substance.
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What is an Atom?•Smallest piece of matter Smallest piece of matter
that that still retains the still retains the propertiesproperties of that of that matter.matter.
•What are they composed What are they composed of?of?
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Timeline
Bohr Model- electrons are found only in specific circular paths, or orbits, around the nucleus.Electron Cloud Model: Probable locations of electrons.MODERN:
Quantum Mechanical Model: Mathematical model describing the behavior of electrons and energy of electrons in various locations around the nucleus.
Subatomic Subatomic ParticlesParticles• Protons• Neutrons• Electrons
NucleusNucleus
7 Atomic Structure
8 Atomic Structure
What makes one element different from another element?
Number of protons.
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Atomic Structure
Rutherford’s Gold Foil experiment led to the discovery of a positive
nucleus.
10 Atomic Structure
ProtonsProtons•Positive ChargePositive Charge•The number of protons determines which The number of protons determines which
element it is.element it is.•All elements have different numbers of All elements have different numbers of
protonsprotons•1 amu1 amu•Composed of quarksComposed of quarks
11 Atomic Structure
Neutron
• Neural charge• Located in the nucleus• 1 amu
• Composed of quarks
Atomic Structure
•Smallest Smallest subatomic subatomic particle.particle.
•1/1800 the 1/1800 the mass of a mass of a proton.proton.
•Orbit nucleus.Orbit nucleus.•Negative Negative ChargeCharge
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Atomic Structure
•Electrons are Electrons are found in found in different levels different levels around the around the nucleus.nucleus.
•These are These are called Energy called Energy Levels or shells.Levels or shells.
•Each energy Each energy level also has level also has “sublevels” or “sublevels” or orbitalsorbitals
13 Atomic Structure
14 Atomic Structure
Electrons Electrons are found are found
in the in the
Electron Electron cloudcloud
surroundinsurrounding the g the
nucleus.nucleus.
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15 Atomic Structure
Each Energy Level Can Hold Each Energy Level Can Hold A Certain Number of A Certain Number of
Electrons!Electrons!Only Only TWO TWO on on the the first first levellevel!!
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Atomic Structure
Different atoms have different Different atoms have different numbers of electrons!numbers of electrons!
Eight Eight on on the the 22ndnd
Each Energy Level Can Hold Each Energy Level Can Hold A Certain Numbers of A Certain Numbers of
Electrons!Electrons!
1717 Atomic Structure
2n2
18 Atomic Structure
Atomic Structure
• Atomic Atomic NumberNumber
• Number of Number of ProtonsProtons
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1
•Atomic MassAtomic Mass
•Sum of Sum of Protons & Protons & NeutronsNeutrons
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The # of Protons determines the identity of an element. All elements have
different number of protons.
Atomic Structure
How can I find out how How can I find out how many electrons an atom many electrons an atom
has?has?•Atom= neutral•So, the number of protons = electrons.
•Atomic number tells you the number of protons.................
•So, it also tells you the number of electrons!
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Atomic Structure
• Practice with a friend…………
Quantum Mechanical Model• Based on quantum theory, which says matter also
has properties associated with waves.
• According to quantum theory, it’s impossible to know the exact position and momentum of an electron at the same time. This is known as the
Uncertainty Principle.
• This model of the atom uses complex shapes of orbitals (sometimes called electron clouds)
– Orbitals: volumes of space in which there is likely to be an electron.
So, this model is based on probability rather than certainty.
Atomic Orbitals• An atomic orbital is a region of space in which there
is a high probability of finding an electron.
• Energy levels of electrons are labeld by principal quantum numbers (n).
• Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.
• Different orbitals have different shapes.
Quantum Numbersn, l, m, s
•Describing electron locations•4 quantum number.•1st-Principle Quantum # = n
–Which energy level the e- is in.– n= 1-7 (there are only 7 energy levels)
•Max # formula= 2n2
• the larger the value of n, the farther away from the nucleus and the higher the energy of the electron.
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2nd quantum number= l• Describes the shape (orbital)• Shapes: s, p, d, f• Each shape “sublevel”
can only have 2 electrons.
• Max electrons in each sublevel:– s=(1x2)2, p=(3x2)6, d=(5x2)10,
f=(7x2)14 # of sublevels
s & p
S (1),p (3), d (5)
# of sublevels (shapes)
F (7)
• 3rd quantum number= m–Describes orientation in space
–x, y, z• 4th quantum number= s
–Describes the spin of the e in the orbital
–Clock or counterclock
• Brain Break• Clip
1. Aufbau Principle: e-
occupy orbitals of the lowest energy first.
22Orbital Filling Diagrams (3 rules)
p.133 text
• Hund’s Rule: one electron in each orbital, then electrons pair up with opposite spins.
• Pauli Exclusion Principal: An orbital may have no more than 2 electrons. 2 e- cannot have the same spin in the same orbital.
22Orbital Filling Diagrams
• Practice:• H, C, Na, S, Ar, K.
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Blocks and Sublevels• We can use the periodic table to predict which sublevel is
being filled by a particular element.
Electron Configuration Notation24
Practice: Write the electron configuration notation.
Name Atomic Number Electron Configuration
• Oxygen 8 1s2 2s22p4
• Aluminum13 1s2 2s22p63s23p1
• Chlorine 17 1s2 2s22p63s23p5
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Electrons and Light Emission• When atoms absorb
energy, electrons move into higher energy levels (excited state).
• When the return to their ground state, the lose energy by emitting light.
• The light emitted is a mixture of a specific frequencies.
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• A quantum of energy is the amount of energy required to move an electron from on energy level to another energy level.
• The higher the ground state, the less energy it take to move to a higher energy level.
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Electrons & Light Emission
• Each frequency is a different color.
• When the frequencies are passed through a prism, the colors are separated & an atomic emission spectrum is created for that element.
• Larger “jump”- more energy-more towards the blue side
• Smaller “jump”- less energy-more towards the red side
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• The flame test is used to visually determine the identity of an unknown metal or metalloid ion based on the characteristic color the salt turns the flame of a bunsen burner
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IsotopesIsotopes are atoms that have the same number of protons and differ only in the
number of neutrons.
Most isotopes are stable but radioactive isotopes are unstable and break down into more stable forms by emitting particles and
energy (radiation). Radiation can be detected, so radioactive isotopes are useful as labels in scientific
research and medical diagnostic procedures.
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Let’s Do some practice problems
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• How do you find this number?
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Calculating Average Atomic Mass
Percent(%) abundance of isotopes
Weighted average= Mass of each isotope x %
abundance of that element
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Atomic Mass of Magnesium
Isotopes Mass of Isotope Abundance 24Mg = 24.0 amu 78.70% = ______
25Mg = 25.0 amu 10.13% = ______
26Mg = 26.0 amu 11.17% = ______
Atomic mass (average mass) Mg = 24.3 amu Mg24.3
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Practice• Gallium is a metallic
element found in small lasers used in compact disc players. In a sample of gallium, there is 60.2% of gallium-69 (68.9 amu) atoms and 39.8% of gallium-71 (70.9 amu) atoms. What is the avg. atomic mass of gallium?
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• A sample of boron consists of 10B (mass 10.0 amu) and 11B (mass 11.0 amu). If the average atomic mass of B is 10.8 amu, what is the % abundance of each boron isotope?
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Counting Atoms
• The Mole
• For a given molecule (atom), one mole is a mass (in grams) whose number is equal to the atomic mass of the molecule (atom)
The Mole
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A counting number (like a dozen)
Avogadro’s number (NA)
1 mol = 6.02 1023 items
What is the Mole?
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The Mole
–1 mole of molecules has a mass equal to the molecular weight in grams.
–A mole of carbon-12 atoms has a mass of just 12 g.
• How many Atoms is that???• 1 mole = 6.022 x 1023 atoms
Avogadro's number Amedeo Avogadro (1776-1856)
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Molar Mass
Mass of 1 mole of an element or compound.
Atomic mass tells the... atomic mass units per atom (amu) grams per mole (g/mol)
1 atom of C = 12.01 amu 1 mol of C = 12.01 g
Round to 2 decimal places
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lithium
aluminum
zinc
6.94 g/mol
26.98 g/mol
65.39 g/mol
Molar Mass Examples
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Molar Conversion Examples How many grams of iron are in
2.25 mol of iron?
2.25 mol Fe 55.85 g Fe
1 mol Fe= 126 g Fe
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Molar Conversion Examples How many moles of calcium are
in 5.0 g of calcium?
5.0 g Ca 1 mol Ca
40.08 g Ca= 0.12 mol Ca
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Examples • 1 mole of Na is the number of atoms in 22.9898g
• 22.9898g is the molar mass
• 1 mole H2O is the number of molecules in 18.015 g H2O
• 1 mole H2 is the number of molecules in 2.016 g H2. Practice:1. How many atoms are in 1 mol of H?2. What is the mass of 1 mol of H?3. How many atoms are in 2 mole of H?4. What is the mass of 2 mol of H?
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More Practice:5. Convert 589 g of Au to moles. 6. Convert 344 grams of Fe to moles.7. What is the mass of 3 moles of KOH?
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Mole Day is October 23rd!
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