Properties of Atoms

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Properties of Atoms
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Atomic Structure Goals
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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 atoms
chemical properties. c. Explain the relationship
of the proton number to the elements 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.
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This will be our FOCUS
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Matter
Mixture
Substance
Element
Compound
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What is an Element?
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• One of the 116 known Pure, un-cutable
  substances.that still retain the properties of
  that substance.

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What is an Atom?
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Clip

• Smallest piece of matter that still retains the
  properties of that matter.
• What are they composed 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.
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Subatomic Particles
Atomic Structure
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• Protons
• Neutrons
• Electrons

Nucleus
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Atomic Structure
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What makes one element different from another
element? Number of protons.
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Atomic Structure
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Rutherfords Gold Foil experiment led to the
discovery of a positive nucleus.
Atomic Structure
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Protons
Atomic Structure
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• Positive Charge
• The number of protons determines which element it
  is.
• All elements have different numbers of protons
• 1 amu
• Composed of quarks

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Neutron
Atomic Structure

• Neural charge
• Located in the nucleus
• 1 amu
• Composed of quarks

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Atomic Structure
Electrons
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• Smallest subatomic particle.
• 1/1800 the mass of a proton.
• Orbit nucleus.
• Negative Charge

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Atomic Structure
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• Electrons are found in different levels around
  the nucleus.
• These are called Energy Levels or shells.
• Each energy level also has sublevels or orbitals

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Atomic Structure
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Atomic Structure
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Clip
Electrons are found in the Electron
cloud surrounding the nucleus.
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Atomic Structure
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Each Energy Level Can Hold A Certain Number of
Electrons!
Only TWO on the first level!
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Atomic Structure
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Different atoms have different numbers of
electrons!
Each Energy Level Can Hold A Certain Numbers of
Electrons!
Eight on the 2nd
2n2
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Atomic Structure
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Atomic Structure
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Atomic Structure
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• Atomic Number
• Number of Protons

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H

• Atomic Mass
• Sum of Protons Neutrons

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The of Protons determines the identity of an
element. All elements have different number of
protons.
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How can I find out how many electrons an atom has?
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• 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!

Atomic Structure
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• Practice with a friend

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Quantum Mechanical Model

• Based on quantum theory, which says matter also
  has properties associated with waves.
• According to quantum theory, its 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.

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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.

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Quantum Numbersn, l, m, s
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• 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
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s p
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S (1),p (3), d (5)
of sublevels (shapes)
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F (7)
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• 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

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• Brain Break
• Clip

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Orbital Filling Diagrams (3 rules)

1. Aufbau Principle e- occupy orbitals of the
   lowest energy first.

p.133 text
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Orbital Filling Diagrams
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• Hunds 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.

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• 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.

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Electron Configuration Notation
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Practice Write the electron configuration
notation.

• Name Atomic Number Electron
  Configuration
• Oxygen 8 1s2 2s22p4
• Aluminum 13 1s2 2s22p63s23p1
• Chlorine 17 1s2 2s22p63s23p5

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Electrons and Light Emission
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• 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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Isotopes
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Isotopes Isotopes 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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Lets Do some practice problems ?
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• How do you find this number?

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Calculating Average Atomic Mass
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• Percent() abundance of isotopes
• Weighted average Mass of each isotope x
  abundance of that element

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Atomic Mass of Magnesium
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• 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

Mg 24.3
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Practice
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• 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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Practice

• 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

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The Mole
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• For a given molecule (atom), one mole is a mass
  (in grams) whose number is equal to the atomic
  mass of the molecule (atom)

What is the Mole?
A counting number (like a dozen) Avogadros
number (NA) 1 mol 6.02 ? 1023 items
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The Mole
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• 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

Amedeo Avogadro (1776-1856)
Avogadro's number
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Molar Mass
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• 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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Molar Mass Examples

• lithium
• aluminum
• zinc

6.94 g/mol 26.98 g/mol 65.39 g/mol
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Molar Conversion Examples
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• 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
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• 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
• How many atoms are in 1 mol of H?
• What is the mass of 1 mol of H?
• How many atoms are in 2 mole of H?
• What is the mass of 2 mol of H?

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• More Practice
• Convert 589 g of Au to moles.
• Convert 344 grams of Fe to moles.
• What is the mass of 3 moles of KOH?

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Mole Day is October 23rd!
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