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The Parts of an Atom

The Parts of an Atom. Chapter 7. History of the Atom. 1910 Ernest Rutherford Scientist behind the famous “Gold Foil Experiment” Fired + charged Helium nuclei at a piece of gold foil. Result: Most of them went straight through the foil, only 1 in 10,000 hit

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The Parts of an Atom

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  1. The Parts of an Atom Chapter 7

  2. History of the Atom 1910 • Ernest Rutherford • Scientist behind the famous “Gold Foil Experiment” • Fired + charged Helium nuclei at a piece of gold foil. • Result: Most of them went straight through the foil, only 1 in 10,000 hit • Why is this important? It helped us determine the shape of an atom.

  3. Rutherford’s Gold Foil Experiment • Most of the nuclei passed through the foil. Some were deflected or bounced straight back. What does this tell us? gold foil helium nuclei helium nuclei

  4. Results of the Gold Foil Experiment: • The atom is mostly “empty space” • The atom contains a central nucleus, which was very dense and had a positive (+) charge

  5. Niels Bohr 1913 • Refined Rutherford’s idea by adding that electrons (which have a negative (-) charge) were located in orbits around the nucleus. • Creates the Bohr model of the atom.

  6. Bohr’s Model electrons in orbits nucleus

  7. The Parts of an Atom • [DEF]: An atom is the smallest unit of matter that retains it’s chemical properties. • Comes from the latin word atomos which means, indivisible

  8. The Parts of an Atom • The two main areas of an atom: • Nucleus • (Think of the Sun) • Electron Shells/Clouds • A.K.A.: Energy Levels (Think of the planets’ orbits)

  9. The Parts of an Atom • The three subatomic particles of an Atom: • Particle 1: The Proton • Charge: Positive (+) • Location: Nucleus • Weight: ~ 1 amu (amu = atomic mass unit)

  10. The Parts of an Atom • The three subatomic particles of an Atom: • Particle 2: The Neutron • Charge: Neutral (0) • Location: Nucleus • Weight: ~ 1 amu

  11. The Parts of an Atom • The three subatomic particles of an Atom: • Particle 3: The Electron • Charge: Negative (-) • Location: Electron Shells • Weight: ~ 0 amu

  12. Atomic Structure Electrons are arranged in Energy Levels or Shells around the nucleus of an atom. 3 2 1

  13. The Parts of an Atom • How the Periodic Table helps: • Atomic Number • Number of Protons • Number of Electrons • Atomic Mass • Subtract Atomic Mass – Atomic Number to determine the number of Neutrons

  14. The Parts of an Atom • Practice Problems: • How many Protons, Neutrons & Electrons do the following elements have: 1) 2) 3) 4) P N E P N E P N E P N E

  15. Valence Electrons & The Periodic Table • Elements in Group 1 & 2 have the same number of valence electrons as their group number. • Elements in Group 3-12 have no rule about valence electrons. • Elements in Groups 13-18 have 10 fewer electrons than their group number.

  16. Valence Electrons 1 2 3 4 5 6 7 8 Varies 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

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