The Atom

1
The Atom
2
How big is an Atom?

• The average size atom (Al) is about 0.00000003
  cm.
• It would take a stack of 50,000 aluminum atoms to
  equal the thickness of a sheet of aluminum foil.
• Thats Small!!!!

3
Whats Inside an Atom?

• An atom is made up of a team of three players
  protons, neutrons, and electrons
• They each have a charge, mass, and a location

4
Protons...

• Charge positive
• Mass 1 amu (atomic mass unit)
• Location Nucleus

5
Neutrons...

• Charge none
• Mass 1 amu (atomic mass unit)
• Location Nucleus

6
Electrons...

• Charge negative
• Mass almost zero
• Location electron clouds

7
Electrons vs Protons

• The electrons negative charge is the same size
  as a protons positive charge.
• They cancel each other out
• 1 -1 0
• Atoms like to have 0 charge.

8
Questions...

• What particles are in the nucleus?
• Explain why atoms are neutral.
• Why do scientists say that most of the mass of an
  atom is located in the nucleus?

9
How Do Atoms of Different Elements Differ?

• Lets compare a Hydrogen atom and a Helium atom

10
Hydrogen...

• Draw one proton.
• Draw a circle around the proton.
• Place one electron on the circle.
• You have just created a hydrogen atom!
• Hydrogen has no neutrons.

11
Helium

• Draw two protons and two neutrons all together.
• Draw an electron orbit around them.
• Place two electrons on the orbit.
• You have just created a helium atom!!!

12
What is different?

• The two different elements have different numbers
  of electrons, protons, and neutrons.
• OK...

13
Are all atoms of an element the same?

• Draw another Hydrogen atom, but this time add a
  neutron.
• It is still Hydrogen because it has only one
  proton, but it has more mass in the nucleus.
• It is called an isotope.

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What is an Isotope?

• Isotope - atoms that have the same number of
  protons but have different numbers of neutrons.
• Some isotopes are radioactive.
• Otherwise they are mostly the same as the regular
  atom.

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How can you tell one isotope from another?

• By their mass numbers.
• mass number protons neutrons.
• Different isotopes will have different mass
  numbers because they have different numbers of
  neutrons.

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Lets see...

• Hydrogen-1 has 1 proton and 0 neutrons.
• Mass Number 1
• Hydrogen-2 has 1 proton and 1 neutron.
• Mass Number 2

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Questions

• List the charge, location, and mass of each
  particle.
• Determine the number of protons, electrons, and
  neutrons in aluminum-27.