Atomic Structure

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Atomic Structure

• Pre-AP 8th Grade Science

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Parts of an Atom

• Protons positive charge 1
• Neutrons do not have a charge (0)
• Electrons negative charge 1-
• Atoms of different elements differ in the number
  of protons they contain.
• Atomic Number number of protons and number of
  electrons in a neutral atom Identifies the
  element!

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A little joke

• A neutron walked into a bar and asked how much
  for a drink. 
• The bartender replied,  "for you, no charge." 
• -Jaime - Internet Chemistry Jokes

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All atoms have 2 common structures
Nucleus
Electron cloud
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Each structure is made of subparticles.
Electron Cloud
protons
nucleus
electrons
neutrons
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Energy Levels

• 1st shell can hold 2 electrons
• 2nd shell can hold 8
• 3rd shell can hold 18

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Electron Cloud

• Protons and Neutrons are found in a small,
  positively charged () center of the atom called
  the nucleus that is surrounded by a cloud
  containing electrons.

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Atomic Mass Unit (AMU)

• The mass of a proton or neutron is about 1 atomic
  mass unit or AMU
• Proton 2000 times larger than an electron.
• The electron cloud makes most of an atoms
  volume (space). Electrons are very tiny.

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1926
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If both protons and neutrons are found in the
nucleus, why is it positive?

1. Neutrons have a positive charge
2. Both neutrons and protons have a positive charge
3. Protons have a positive charge and neutrons have
   no charge
4. Neutrons have a negative charge

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Atomic Structure VideoDiscovery Education
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The number of protons in the nucleus of an atom
is that atoms atomic number.
Carbon has 6 protons. The atomic number of
carbon is 6.
The number of protons plus the number of neutrons
in the nucleus of an atom is its atomic mass.
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How many protons are in Magnesium?

1. 25
2. 24.31
3. 11
4. 12

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What is the atomic mass of Potassium?

1. 39.10
2. 19
3. 15
4. 30.97

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To find the number of neutrons in an atom,
subtract the atomic number from the atomic mass.
16 Atomic mass (protons neutrons) - 8 Atomic
number (protons) ___ 8 Number of neutrons
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A Little Saying to help you remember

• A
• P
• E

• M
• A
• N

tomic
ass
rotons
tomic
lectrons
eutrons
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8
Atomic Number
8
Protons
16
Atomic Mass









8
Neutrons
2
Energy Levels
oxygen atom
8
Electrons
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What is the number of neutrons in Potassium?

• 39
• 19
• 20
• 21

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How many neutrons are in Fluorine?

• 9
• 19
• 10
• 28

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Valence Electrons

• Electrons farthest away from the nucleus are most
  loosely held.
• Ranges from 1 to 8 valence electrons
• Many properties of the atom, and therefore of an
  element, are determined by the number of valence
  electrons.

• http//www.tutorvista.com/content/science/science-
  i/structure-atom/valence-shell-electron.php

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Electron Dot Diagrams

• Also called Lewis Structure
• Used to represent valence electrons
• Made up of the element symbol surrounded by dots
• Each dot stands for one valence electron

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Chemical Bonds

• Valence electrons can form chemical bonds, a
  force that holds atoms together.
• When bonds form, valence electrons are either
  transferred or shared between atoms.
• When atoms end up with 8 or 0 valence electrons,
  they become more stable or less reactive.