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  • 1. Introduction to Atomic Structure
  • 2. ATOMS
    • Considered the building blocks of matter
    • Made up of three main subatomic particles:
      • Protons
      • Neutrons
      • Electrons
    • All protons are identical, regardless of the element in which they are found. This is also true for neutrons and electrons.
  • 3. Nucleus
    • Atoms have a small, dense nucleus in the middle but most of the atom is nothing more than empty space!
    • Extremely small in size relative to the atom but it contains 99.99% of the atom’s mass.
      • If the atom were enlarged to the size of a football stadium, the nucleus would be the size of a bee!
    • Contains 2 of the 3 subatomic particles
      • Protons (+ charged particles)
      • Neutrons (neutrally charged particles)
  • 4. Atomic Mass Units
    • Mass of proton = 1 amu (atomic mass unit)
    • 6 23 amu = 1 gram
    • Neutrons have slightly more mass than protons but they are considered equal.
    • Mass of neutron still = 1 a.m.u.
    • Mass of electron is tiny even on an atomic scale (0.0006 amu).
  • 5. Atomic #
    • # of protons in nucleus determines the atomic number of an element.
    • This identifies the element!
    • Hydrogen--Atomic #1 = 1 proton
    • Helium--Atomic #2 = 2 protons
    • Oxygen--Atomic # 8 = 8 protons
      • All atoms with 8 protons MUST be oxygen!
      • The # of protons in an atom CANNOT be changed (otherwise, you will have a different element!)
  • 6. Isotopes
    • Even though the # of protons will never change, the # of neutrons can vary from atom to atom.
    • Atoms of the same element that have the same # of protons, but different number of neutrons are called isotopes .
    • Every single atom is going to be an isotope of that element!
  • 7. Isotopes
    • Hydrogren has 3 different isotopes (all of them have 1 proton)
      • Protium (no neutrons)
      • Deuterium (1 neutron)
      • Tritiuim (2 neutrons)
    • Every atom of “H” is going to be one of these isotopes!
  • 8. Mass number
    • Mass # of an atom is the sum of the protons and neutrons in its nucleus.
    • The electrons are ignored because they are so small!
    • The mass number varies for different isotopes of an element.
  • 9. Mass number
    • Carbon has two known isotopes:
      • Carbon-12 (6 protons and 6 neutrons) (6 electrons)
      • Carbon-14 (6 protons and 8 neutrons) (6 electrons)
  • 10. Atomic Mass
    • Any sample of an element as it occurs in nature contains a mixture of isotopes.
    • The atomic mass of an element is the average mass of all the isotopes of that element. Therefore, the atomic mass is usually not a whole number.
  • 11. Atomic Mass
    • For example, the atomic mass for carbon is 12.011
    • Remember, there are two naturally-occurring isotopes: C-12 and C-14
    • Since the atomic mass is much closer to “12”, this tells you that there are MANY more atoms of Carbon-12 than there are Carbon-14.
  • 12. Electrons
    • Electrons have a negative charge and are found outside of the nucleus.
    • In an uncharged atom, the # of electrons = # of protons
    • Always assume that the atom has a zero charge and is neutral.
  • 13. Ions
    • Sometimes, atoms will either lose or gain electrons.
    • When this happens, they do not equal the # of protons, and the atom becomes positively or negatively “charged”.
    • These charged atoms are called ions .
  • 14. Electron Cloud
    • Space in which electrons are found.
    • Arranged in energy levels:
    • Lower energy level = closer to the nucleus
    • Higher energy level = further from nucleus
      • 1 st energy level - 2 electrons.
      • 2 nd energy level -8 electrons
      • 3 rd energy level -18 electrons
  • 15. Electron Cloud
    • An atom’s bonding ability is determined by the arrangement of electrons in the outermost energy level.
    • These are called valence electrons.
    • Atoms that have only one electron or those that only need one electron are much more likely to bond.
    • Some elements have a complete set of electrons and will not bond (Noble Gases)
  • 16. Quarks
    • It is possible to get even smaller than these three subatomic particles.
    • Current theory states that protons and neutrons are themselves made up of even smaller particles known as quarks.
    • There better our technology gets, the more subatomic particles there are being discovered.