Unit 3 Atomic Theory

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Unit 3Atomic Theory
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Atom

• Smallest particle possessing the properties of an
  element.

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Nucleus

• Dense, positively charged central region that
  contains protons and neutrons.

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Protons

• Positively charged subatomic particles that are
  found in the nucleus

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Neutrons

• Neutral subatomic particles (have no electrical
  charge) that are found in the nucleus.

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Electron Cloud

• Different energy levels surrounding the atoms
  nucleus where electrons can be found.

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Electrons

• Negatively charged subatomic particles that
  surround the nucleus.

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Atomic Number

• The number of protons in an atom.

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Atomic Mass

• The relative average mass of an atom of an
  element as found in nature.

Atomic mass of protons of neutrons.
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II Atomic Particles
Particle Mass Location Charge
Proton 1 AMU Nucleus Positive
Neutron 1 AMU Nucleus Neutral
Electron 0 AMU Electron cloud Negative
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Isotopes

• Atoms of the same element that have a different
  number of neutrons.

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Isotopes

• Two (2) or more atoms of the same element with a
  different mass.
• Percent () abundance
• Protium, Deuterium, Tritium 99.985,
  0.015, 0

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Self Check

• 1. What two subatomic particle are found in the
  nucleus?
• A. Neutrons and Electrons
• B. Protons and Electrons
• C. Neutrons and Protons
• D. Neutrons only

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Self Check

• 2. The atomic number is equal to the _______.
• A. Number of neutrons in an atom.
• B. Number of electrons in an atom.
• C. Number of neutrons plus the number of
  protons in an atom.
• D. Number of protons in an atom.

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Self Check

• 3. Isotopes are atoms of the same element that
  have a different number of ______.
• A. Neutrons
• B. Protons
• C. Electrons
• D. All of the above

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Self Check

• 4. The element with an atomic number of 14 is?
• A. Nitrogen
• B. Silicon
• C. Aluminum
• D. Sulfur

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Important Number Stuff

• Atomic number is equal to the number of protons
  (and electrons in a neutral atom)
• Atomic Mass is the sum of protons and neutrons

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Examples
Element protons neutrons electrons Ave. Atomic mass
Boron 5 6 5 10.811
Sulfur 16 16 16 32.006
Gold 79 118 79 196.96
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Samplelook at 2_weighted ave.

• Of 100 marbles
• 25 have a mass of 2.00g
• 75 have a mass of 3.00g
• What is the average mass?
• 25 0.25 75 0.75
• (0.25 x 2.00) (3.00 x 0.75) Ave Mass
• 0.5 2.25 2.75

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Sample with Atoms

• Copper 63 amu 69.17
• Copper 65 amu 30.83
• Calculate the Average atomic mass

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Continued

• Copper 63 amu 69.17
• Copper 65 amu 30.83
• Calculate the Average atomic mass

• (63 x 0.6917) (65 x 0.3083)
• 63.617 AMU
• Check on periodic table

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Ions

• Electrically charged atoms or groups of atoms.
• Cations positively charged
• Anions negatively charged

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I Models of the atom over time

• Democritus fifth century BC Philosopher
• First to describe matter as made of tiny
  particles
• John Dalton Billiard ball theory 1803
• Atom small solid sphere
• In an element all the same sphere
• Different elements different sphere
• Compounds different spheres combined in
  different ratios

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Continued

• JJ Thompson 1897 Plum Pudding model
• Atom sphere of and particles
• Discovered the electron Nobel prize

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Valence Electrons

• Electrons found in the outer-most energy level of
  the electron cloud.
• Identify patterns using periodic table based on
  element location

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Continued

• Ernest Rutherford 1908
• Atom mostly empty space
• nucleus
• - electrons outside
• Niels Bohr 1913
• Electrons traveled in circular orbits

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Continued

• Electron Cloud Model 1920s
• Atom Dense nucleus of protons and neutral
  neutrons.
• Electrons surround nucleus in clouds of
  different NRG levels.
• (NRG Numerical Renormalization Group)

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Elements on the Periodic Table
1
Hydrogen
H
1.008
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Self Check

• 5. Draw a picture of what Iron in its neutral
  state would look like on the periodic table.

Hint
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Self Check Answers

• 1. C
• 2. D
• 3. A
• 4. B
• 5.

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Iron
Fe
55.85
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III. Molar Conversions
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A. What is the Mole?

• A counting number (like a dozen)
• Avogadros number (NA)
• 1 mol 6 ? 1023 items

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A. What is the Mole?
HOW LARGE IS IT???

• 1 mole of hockey pucks would equal the mass of
  the moon!

• 1 mole of basketballs would fill a bag the size
  of the earth!

• 1 mole of pennies would cover the Earth 1/4 mile
  deep!

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B. Molar Mass

• The mass of 1 mole of an element or compound.
  Round to nearest whole number (except chlorine)
• Atomic weight label
• amu/atom or g/mol
• Molecular weight label
• amu/molecule or g/mol

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B. Molar Mass Examples

• carbon
• aluminum
• zinc

12 g/mol 27 g/mol 65 g/mol
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B. Molar Mass Examples

• water
• sodium chloride

• H2O
• 2(1) 16 18 g/mol
• NaCl
• 23 35.5 58.5 g/mol

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B. Molar Mass Examples

• sodium bicarbonate
• sucrose

• NaHCO3
• 23 1 12 3(16) 84 g/mol
• C12H22O11
• 12(12) 22(1) 11(16) 342 g/mol

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C. Molar Conversions
molar mass
6 ? 1023
(g)
(atoms/molecules)
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C. Molar Conversion Examples

• How many moles of carbon are in 26 g of carbon?

26 g C
1 mol C 12 g C
2.17 mol C
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C. Molar Conversion Examples

• How many molecules are in 2.50 moles of
  C12H22O11?

2.50 mol C12H22O11
6 ? 1023 molecules 1 mol
1.5 ? 1024 molecules C12H22O11
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C. Molar Conversion Examples

• Find the mass of 2.5 moles of NaHCO3.

2.5 mol NaHCO3
84 g 1 mol
210 g NaHCO3
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Patterns on the Periodic Table