Chapter 17 - cp

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Chapter 17 - cp

• Atoms

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4.2/4.3 The Structure of the Atom Modern Atomic
Theory

• JOURNAL
• QUIETLY work on the Atomic Math worksheet FIRST
• Then, work on theNot So Bohr-ing Atoms
  Worksheet from the back table.
• Use the Periodic Table I gave you to help you.

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Studying Atoms

• ANCIENT GREEKS-
• DEMOCRITUS
• atomos indivisible, uncut
• Different types of atoms with specific properties
• ARISTOTLE
• Only 4 elements
• No limit to divisions

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Studying Atoms

• DALTONS ATOMIC THEORY all matter is made of
  particles that cannot be divided
• Evidence
• Compounds have fixed compositions
• H2O
• Chemical reactions are a rearrangement of solid
  atoms.

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Studying Atoms

• THOMSONS ATOMIC THEORY all matter is made of
  particles that CAN be divided
• EVIDENCE
• Particles collected on metal plate
• The particles ALWAYS had a mass 1/2000 of a
  Hydrogen atom.
• The beam was always attracted to the positive side

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Thomsons plum pudding Atomic Model
Explained neutral atoms with charges
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Studying Atoms

• RUTHERFORDS ATOMIC THEORY all atoms positive
  charge is concentrated in the nucleus

Thomsons plum pudding Atomic Model
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Studying Atoms

• RUTHERFORDS ATOMIC THEORY all atoms positive
  charge is concentrated in the nucleus
• Discovered
• Uranium emits fast moving positive particles

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Studying Atoms

• RUTHERFORDS ATOMIC THEORY all atoms positive
  charge is concentrated in the nucleus
• If you shoot these positive particles at other
  atoms (Thomsons plum pudding atom), what would
  happen to the particle?
• SHOULD GO STRAIGHT THROUGH!!

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Studying Atoms Gold Foil Experiment
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4.1 The Gold Foil Experiment
RUTHERFORDS ATOMIC THEORY all atoms positive
charge is concentrated in the nucleus
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Studying Atoms Modern Atomic Theory

• Bohr Atom
• Electrons are in energy levels
• Electrons move when they gain or lose energy
• (example)

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• Parts of an ATOM
• Subatomic particles distinguished by mass,
  charge and location

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• Subatomic particle PROPERTIES
• Protons (p)
• In the nucleus
• Charge of 1
• Mass of 1
• DEFINES THE ELEMENT
• (equals the ATOMIC NUMBER)

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• Protons (p)
• Atoms of DIFFERENT elements have DIFFERENT
  numbers of protons

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• Subatomic particle PROPERTIES
• Neutrons (n)
• In the nucleus
• NO charge
• Mass of 1
• Protons neutrons the ATOMIC MASS

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• Neutrons (n)
• Atoms of the same element with DIFFERENT numbers
  of neutrons are called
• ISOTOPES

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• Neutrons (n)
• ISOTOPES of Hydrogen. Same Atomic , different
  Mass

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• Electrons (e-)
• In ENERGY LEVELS around the nucleus
• Charge of 1-
• Mass of 1/1836 of a p
• Equal to the number of protons
• The outermost shell of electrons is called the
  VALENCE SHELL which holds the VALENCE ELECTRONS.

Take out Bohr Diagram Sheet.
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• Electrons (e-)
• Change ENERGY LEVELS when the atom GAINS or LOSES
  energy

The most stable electron arrangement
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• Electrons (e-)
• CurrentTheory Electron Cloud Model (p116-17)
• Orbitals that show most PROBABLE location of
  electrons

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• Electrons (e-)
• Atoms of the same element with different number
  of ELECTRONS are called IONS

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• IONS form to make the outermost shell stable

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4.2/4.3 The Structure of the Atom Modern Atomic
Theory

• OCTET RULE
• Take out a lined sheet of paper, draw a circle
  for a nucleus and then three rings around the
  nucleus.

2 electrons in 1st shell
Protons and neutrons in nucleus
8 electrons in 2nd shell
8 electrons in 3rd shell
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Atomic Number Practice

• Use your periodic table to find the atomic number
  of the following elements
• Aluminum (Al)
• Titanium (Ti)
• Tin (Sn)
• Osmium (Os)
• Erbium (Er)
• How many protons does each atom have?
• The number of protons are equal to the atomic
  number.

Al 13
Ti 22
Sn 50
Os 76
Er 68
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Mass Number

• The mass number of an atom is the sum of the
  number of protons and neutrons in the nucleus.

Element Protons Neutrons Mass Number
Boron 5 6 56
Carbon 6 6 66
Oxygen 8 8 88
Sodium 11 12 1112
Copper 29 34 2934
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12
16
23
63
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Practice

• Determine the number of protons and neutrons in
  the following atoms
• Lithium Atomic Number 3
• Mass Number 7
• Argon Atomic Number 18
• Mass Number 39
• Strontium Atomic Number 38
• Mass Number 88

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Atomic Number Mass Number

• If you know the atomic number and mass number,
  you can determine the number of neutrons.
• Mass Number
• - Atomic Number
• Number of Neutrons

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Answers

• Determine the number of protons and neutrons in
  the following atoms
• Lithium Protons 3
• Neutrons 7 3 4
• Argon Protons 18
• Neutrons 39 18 21
• Strontium Protons 38
• Neutrons 88 38 50

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Neutral Atoms

• In the nucleus, which particles have charge?
• Protons
• What charge do they have?
• Positive
• What particle is opposite that charge?
• Electrons

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Neutral Atoms

• In the atom
• The number of protons equals the number of
  electrons.
• Li has 3 protons, so has a charge of 3.
• Li also has 3 electrons that add up to -3.
• ADDED TOGTHER, the overall charge is
• (3) (-3) 0, so the atom is neutral.

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Practice

• Determine how many electrons the following atoms
  have
• Magnesium, Protons 12
• Beryllium, Protons 4
• Nitrogen, Atomic Number 7
• Bromine, Atomic Number 35

12 Electrons
4 Electrons
7 Electrons
35 Electrons
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Bohr Models of the Atoms

• Each atom has shells in which the electrons can
  fit.
• 1st Shell fills to 2 electrons
• 2nd Shell fills to 8 electrons
• 3rd Shell fills to 18 electrons
• 4th Shell fills to 32 electrons
• Start filling the smallest/closest shell first.

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REVIEW

1. Draw a Bohr Atom Model of Hydrogen, Carbon, and
   Oxygen on the back of your worksheet.
2. Which subatomic particles belong in the nucleus?
3. Which subatomic particles belong on the rings?
4. What is the difference between ground state and
   excited state of an atom?