electron arrangement in atoms

• What do electron shells contain?

  Sub-shells and orbitals
• In the modern model of the atom, where are electrons found?

  In specific energy levels known as shells
• How does the energy of electrons vary with distance from the nucleus?

  Further shells hold higher energy electrons
• What are the labels for sub-shells?

  s, p, d, and f
• What defines an orbital?

  Region with high probability of finding an electron
• How many electrons can an orbital accommodate?

  Up to two electrons with opposite spins
• What is the capacity of each sub-shell type to hold electrons?

  • s: 2 electrons
  • p: 6 electrons
  • d: 10 electrons
  • f: 14 electrons
• What is the distribution of sub-shells across the first four shells?

  1. Shell 1: 1s, 2 electrons
  2. Shell 2: 2s, 2p, 8 electrons
  3. Shell 3: 3s, 3p, 3d, 18 electrons
  4. Shell 4: 4s, 4p, 4d, 4f, 32 electrons
• What is the arrangement of electrons in an atom called?

  Electron configuration
• How can electron configurations be depicted?

  1. Sub-shell notation
  2. Electrons-in-boxes notation
• How is sub-shell notation represented?

  Using superscripts for electron counts
• How is electrons-in-boxes notation represented?

  • Orbitals as boxes
  • Electrons as arrows
  • Opposite arrows for opposite spins
• Why are electron configurations arranged in a specific way?

  To minimize the overall energy of the atom
• What is the electron configuration of calcium?

  1s2 2s2 2p6 3s2 3p6 4s2
• Why is the 4s sub-shell filled before the 3d sub-shell?

  4s has lower energy than 3d orbitals
• What is the rule for occupying orbitals of equal energy?

  • Electrons occupy singly before pairing
  • Pairing occurs only with opposite spins
• What happens when two electrons occupy the same orbital?

  They must have opposite spins
• What is the abbreviated electron configuration of calcium using noble gas notation?

  [Ar] 4s2
• What are the unusual electron configurations for chromium and copper?

  Cr: 3d5 4s1; Cu: 3d10 4s1
• Why do chromium and copper have unusual electron configurations?

  Configurations with half-filled or fully filled d sub-shells are favorable
• When transition metals form ions, from which orbital do electrons get lost first?

  From the 4s orbital