CHEM ST

• Who proposed the triads in the periodic table?

  Johann Döbereiner
• What did John Newlands’ Law of Octaves state?

  Every eighth element repeats properties
• When did Dmitri Mendeleev develop his periodic table?

  1869
• How did Henry Moseley revise the periodic table?

  By organizing elements by atomic numbers
• What are the periodic trends in the periodic table?

  1. Atomic Radius: Increases right to left, down a group
  2. Ionization Energy: Increases left to right, bottom to top
  3. Electronegativity: Increases left to right, bottom to top
  4. Electron Affinity: More negative left to right, less negative bottom to top
• What is the atomic radius?

  Distance from nucleus to outermost electron
• What trend does ionization energy follow?

  Increases from left to right, bottom to top
• What is electronegativity?

  Ability to attract electrons in a bond
• How does electron affinity change across the periodic table?

  More negative from left to right, less negative bottom to top
• What are the properties of reactive and non-reactive metals?

  Reactive Metals:

  • React quickly, even violently
  • Examples: Sodium, Potassium, Iron
  • Low ionization energy

  
  

  Non-Reactive Metals:

  • Rarely undergo chemical reactions
  • Examples: Gold, Platinum, Silver
  • High ionization energy
• Who proposed the Rutherford model of the atom?

  Ernest Rutherford
• What does the Rutherford model describe?

  Dense nucleus with randomly orbiting electrons
• What did Bohr's model introduce about electron orbits?

  Electrons orbit at fixed energy levels
• What does the quantum mechanical model describe?

  Probability of finding electrons in orbitals
• What principle did Heisenberg propose?

  Principle of uncertainty
• What do atomic orbitals represent?

  Regions where electrons are likely found
• What are the types of atomic orbitals?

  1. s-Orbital: Spherical shape, all energy levels
  2. p-Orbital: Dumbbell shape, three orientations
  3. d-Orbital: Complex shapes, five orientations
  4. f-Orbital: More complex, seven orientations
• What does the principal quantum number (n) represent?

  Overall energy of each orbital
• What does the azimuthal quantum number (l) indicate?

  Shape of an electron's orbital
• What values can the magnetic quantum number (m1) take?

  Integer values from -l to l
• What does the electron spin quantum number (ms) describe?

  Direction and magnitude of electron's spin
• What are the important rules for quantum numbers?

  1. Quantum numbers are integers except for ms.
  2. Lowest value of n is 1.
  3. l can range from 0 to n-1.
  4. m can be any integer from -l to +l.
  5. ms can only be +1/2 or -1/2.
• What is electron configuration?

  Arrangement of electrons in an atom's orbitals
• What does the Aufbau Principle state?

  Electrons fill lowest energy orbitals first
• What does the Pauli Exclusion Principle state?

  Each orbital holds two electrons with opposite spins
• What does Hund’s Rule state?

  Electrons fill singly in degenerate orbitals first