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Chapter 3

Atoms and Moles. Chapter 3. Atomic Theory. All matter is made of atoms Law of definite proportions Water is 88.8 % oxygen and 11.2 % hydrogen Law of conservation of mass Mass cannot be created or destroyed Law of multiple proportions

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Chapter 3

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  1. Atoms and Moles Chapter 3

  2. Atomic Theory • All matter is made of atoms • Law of definite proportions • Water is 88.8 % oxygen and 11.2 % hydrogen • Law of conservation of mass • Mass cannot be created or destroyed • Law of multiple proportions • CO , CO2 / C6H12O6 , C12H22O11 / H2O , H2O2

  3. Dalton’s Atomic Theory • All matter is made of extremely small particles called atoms. • Atoms of a given element are identical in their properties. • Atoms cannot be created, destroyed, or subdivided. • Atoms of different elements combine in simple whole-number ratios to form compounds. • In chemical reactions, atoms are combined, separated, or rearranged.

  4. Discovery of the electron Electrons were discovered in a Cathode Ray Tube Electrons are very small particles that have a negative charge

  5. Original model of an atom “Plum pudding” model Electrons were embedded in a positively charged ball of matter

  6. Discovery of the nucleus Rutherford shot a stream of positive particles at a piece of gold foil and expected the particles to go right through the atoms of gold.

  7. Rutherford’s gold foil experiment He expected most of the particles to go straight through but some of the particles bounced straight back. Something very dense and positively charged had to be the reason it bounced back.

  8. New model of the atom Old model New and improved model The atom is very large compared to the size of the nucleus

  9. Atomic Nucleus Protons are positively charged particles Neutrons have no charge - neutral

  10. Counting Subatomic Particles • Atomic number = number of protons • Protons = electrons • Atomic mass = protons + neutrons • Isotope – atoms of a certain element that have a different mass because it has a different number of neutrons.

  11. Where are the electrons • Electrons are found in 3-dimensional spaces around the nucleus called orbitals. • We use 4 quantum numbers to tell: • The distance from the nucleus • The shape of the orbital • The relationship of the orbitals with the x,y,z axes • The spin of the electrons

  12. Principal Quantum Number • Indicates the main energy level • Values = 1 – 7 • This shows how far the orbital is from the nucleus.

  13. Orbital Quantum Number • Indicates the shape of the orbital • 4 shapes • s, p, d, f

  14. Orbital shapes

  15. P orbital

  16. Magnetic Quantum Number • Indicates the orientation of the orbitals on the x, y, and z axes. • How many orbitals there are • s – 1 • p – 3 • d – 5 • f – 7

  17. Spin Quantum Number • Electrons spin in opposite direction • (+1/2, -1/2) • 2 electrons can fit in each orbital

  18. Order of orbital filling

  19. Electron Configuration • Oxygen – 8 electrons • 1s22s22p4 • Sodium – 11 electrons • 1s22s22p63s1 • Argon – 18 electrons • 1s22s22p63s23p6 • Arsenic – 33 electrons • 1s22s22p63s23p64s23d104p3

  20. Mole • 1 mole of any substance has 6.02 x 1023 atoms • (Avogadro’s number) • 1 mole of any substance is equal to it’s mass on the periodic table in grams. • (Molar mass)

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