Variation in Atomic Structure: Isotopes and Ions

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Variation in Atomic Structure Isotopes and Ions

• Monday November 14th and Tuesday November 15th

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Question

• The mass of an atom of an element can change
  without changing the element
• What subatomic particles must change in order
  for this to occur?
• Neutrons changing the protons would change the
  element!!!

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Isotopes

• Element with same amount of protons but
  different amounts of neutrons.

BERYLLIUM ISOTOPES
proton
neutron
electron
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EXAMPLE OF AN ISOTOPE
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Average Atomic Mass

• Average mass of all isotopes of an element
• Relative to the other elements around.
• Determined by taking the sum of mass of all the
  isotopes multiplied by their relative abundances

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Calculating Atomic mass

• Example Rubidium has two common isotopes, 85Rb
  and 87Rb. If the abundance of 85Rb is 72.2 and
  the abundance of 87Rb is 27.8, what is the
  average atomic mass of rubidium?
• ? (85 amu X .722) (87 amu X .278)
• 61.37amu 24.186 amu)
• Answer 85.56 amu

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Practice Magnesium has three isotopes

• Magnesium-24 78.70 abundant
• Magnesium-25 10.13 abundant
• Magnesium-26 11.17 abundant
• Determine average atomic mass of magnesium.
  Units are amus

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How are ions produced?

• Elements gain or lose electrons
• Valence electrons- outer energy level electrons
• Octet Rule- All elements want to be like the
  noble gases (group 18), so they gain or lose
  electrons in order to become stable.
• Column of valence electrons from 1-8
• Exception- Helium- has 2 valence electrons
• Determined from electron dot diagrams

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Electron Dot Diagrams

• Steps to follow
• 1) Write the symbol of the element listed.
• Surround the symbol with valence electrons.

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Electron Dot Diagrams of first 20 elements
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What are ions?

• Atoms of an element that differ in electrons
• Two types
• Cations- lose electrons become positively
  charged
• Column 1 loses 1
• Column 2 loses 2
• Column 3 loses 3
• Anions- gain electrons become negatively charged
• Column 15 gains 3
• Column 16 gains 2
• Column 17 gains 1
• Column 18 stable

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Writing Ions

• Write the elements symbol
• Using a superscript, write a positive or negative
  charge.
• Positive- loses electrons
• Negative- gains electrons
• Write the number lost or gained next to the
  charge.

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SOME ATOMS GAIN ELECTRONS
ATOMS IONIC CHARGE PROTONS - ELECTRONS
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-
-
-
-
-
-
-
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-
-
-
-
-
-
-
-
-
O-2
O
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Making Ions Practice

• Draw the electron dot diagrams and the ions
  formed by the following elements
• Hydrogen
• Lithium
• Magnesium
• Oxygen
• Aluminum
• Phosphorus
• (Hint Ions should include the elements symbol
  and a superscript charge showing the amount of
  electrons gained or lost)

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The Location of Electrons

• Wednesday November 15th and Thursday November
  16th

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Energy Levels

• Energy levels- determine the amount of energy an
  electron has.
• Energy levels n quantum number
• n 1 1st energy level
• n 2 2nd energy level
• n3 3rd energy level
• All the way up to the 7th energy level

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Sublevels

• Organized on
• the periodic table
• into S,P,D, F
• Energy level
• of sublevels

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S Sublevel
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P Sublevel
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Orbitals

• probable location to find an electron
• n2 of orbitals for each energy level
• S 1 orbital P 3 orbitals
• D 5 oribtals F 7 orbitals
• Three rules to follow when electrons fill
  orbitals.
• Aufbau Principle
• Each electron occupies lowest energy orbital
  first
• Pauli Exclusion Principle
• two electrons can occupy 1 orbital
• Hunds Rule
• Electrons occupy each orbital with one electron
  before filling the orbital with two

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• To Review
• Electrons fill to
• become stable.
• No more than 2
• electrons per orbital
• 2n2 of electrons
• per energy level

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Electron Configurations

• Displays the following
• of each energy level
• letter of each sublevel
• of each electron in that sublevel as a
  subscript

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Electron Configurations Examples

• Hydrogen
• 1s1
• Helium
• 1s2
• Lithium
• 1s2 2s1
• Beryllium
• 1s2 2s2

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More Examples

• Boron
• 1s2 2s2 2p1
• Carbon
• 1s2 2s2 2p2
• Nitrogen
• 1s2 2s2 2p3
• Oxygen
• 1s2 2s2 2p4
• Fluorine
• 1s2 2s2 2p5
• Neon
• 1s2 2s2 2p6

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In-class Practice

• Draw electron configurations for the rest of the
  first 20 elements on the periodic table.

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Bohr Models

• Friday November 18th and Monday November 28th

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Making Bohr Models.

• Determine the of protons, neutrons and
  electrons in the element.
• Draw a circle to represent nucleus. Inside of
  circle, write of protons and neutrons.
• Draw circles around the nucleus based on how many
  levels the element has.
• Insert electrons according to the rules learned
  about electron location.
• 1st energy level 2 electrons
• 2nd energy level 8 electrons
• 3rd energy level 8 electrons (can be up to 18)
• 4th energy level 8 electrons (can be up to 32)

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Bohr Model Practice

• Hydrogen-
• Helium-
• Lithium-

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Draw Bohr Models for the rest of the 1st 20
elements.
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Homework

• Chapter Review
• Pennium Lab