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Valence and Core Electrons

Valence and Core Electrons. To find valence electrons , just look at the elements GROUP number Nitrogen is in group 17, so it has 7 valence electrons To find the core electrons total number of electrons– valence electrons 54 Xe  54 – 8 = 46 core 5 B  5 – 3 = 2 core.

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Valence and Core Electrons

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  1. Valence and Core Electrons • To find valence electrons, just look at the elements GROUP number • Nitrogen is in group 17, so it has 7 valence electrons • To find the core electrons • total number of electrons– valence electrons 54Xe  54 – 8 = 46 core 5B  5 – 3 = 2 core

  2. Quantum Model • We already knew that electrons were divided into shells. • n = 1 (1st shell) • n = 2 (2nd shell) • n = 3 (3rd shell) • The quantum model breaks up each electron shell into subshells.

  3. Quantum Model • These subshells represent the area where electrons are most probably located. • Because electrons travel in waves, it is impossible to know the exact position of an electron at any given time. Heisenberg Uncertainty Principle

  4. Quantum Model Subshells • Each subshell has: • A specific name • A maximum capacity for electrons

  5. Quantum Model KEY s subshells p subshells 10 e- d subshells 2e- f subshells 6 e- 2 e- 6 e- 2 e-

  6. Electron Configurations Shorthand notation to keep track of the electrons in an atom

  7. Electron Configurations Li: 1s22s1 electrons in each subshell Superscripts add up to total number of electrons for that atom Energy Level subshell

  8. Electron Configurations • The sequence is the same each time because electrons must fill up the lowest energy levels first. Aufbau Principle German for “building up”

  9. Energy Levels

  10. Periodic Table and Electron Configurations

  11. Quick Check What is the lowest energy level? Which energy level is higher: 2p or 3s? Which energy level is higher: 4s or 3d?

  12. Noble Gas Shortcut • Electron configurations get really long. • To save time, we can use noble gases at the end of each period to represent all the filled subshells before that spot on the table.

  13. Homework Q’s Write shorthand electron configurations for: 1) nickel 2) calcium 3) strontium 4) magnesium 5) barium 6) titanium 7) 1s22s22p63s23p64s1

  14. You Try It • Rb • Br • Cs • Ba • Sn • 1s22s22p63s23p64s23d1 • 1s22s22p63s23p64s1

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