Valence Electrons

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  • 1. Valence Electrons
  • 2. What is a Valence Electron? Valence electrons are the electrons in the outer shell that bond with other atoms
  • 3. What is a Valence Electron? Valence electrons are the electrons in the outer shell that bond with other atoms = valence electron
  • 4. What is a Valence Electron? Valence electrons are the electrons in the outer shell that bond with other atoms = valence electron
  • 5. What is a Valence Electron? Valence electrons are the electrons in the outer shell that bond with other atoms Core electrons are under valence electrons = valence electron
  • 6. Outer Shells of Electrons The number of valence electrons determines an element’s chemical properties For example, the noble gases on the right side of the periodic table are inert Inert = do not react with other atoms
  • 7. Noble Gases Noble gases are inert because they have 8 outer shell (=valence) electrons Having 8 outer shell electrons means the outer shell is full, and therefore can’t react
  • 8. Periodic Table Groups Columns on the periodic table are called GROUPS Elements in the same group have similar chemical properties. This is because each group has the same number of valence electrons
  • 9. Valence Electrons in Groups Elements in the periodic table are arranged in groups. Each group has the same number of valence electrons…. Group 5A Group 1A Group 2A Group 4A Group 3A Group 7A Group 6A Group 8A Group 1A has 1 valence electron, group 2A has 2 valence electrons, group 3A has 3 valence electrons……….
  • 10. Importance of Valence Electrons The entire periodic table is arranged according to the number of valence electrons each element has!! The reason they arrange the periodic table this way is because elements in each group react similarly (=same)
  • 11. Octet Rule The octet rule states that atoms like to have 8 valence electrons. Atoms that have 8 outer shell electrons are stable and non reactive. The noble gases (group 8A) are stable because they all have 8 valence electrons
  • 12. Lewis Structures Lewis structures show ONLY valence electrons. Examples: Sodium (Na) is in group 1A, so we know it has 1 valence electron. Group 1A is known as the alkali metals Beryllium (Be) is in group 2A, so we know it has 2 valence electrons. Group 2A is known as the alkaline earth metals
  • 13. Lewis Structures Lewis structures for oxygen Oxygen is in group 6A, so it has 6 valence electrons.
  • 14. How to Draw Lewis Structures 1) Look at the element you want to draw the structure for and see what group it is in. 2) Draw dots around the symbol according to how many valence electrons it has. Example: Draw a Lewis Structure for calcium 1) We see calcium (Ca) is in group 2A, so it has 2 valence electrons 2) Ca
  • 15. Filling Electron Orbitals Electrons fly around atoms in their electron orbitals There are S, P, D and F orbitals We will only study 1S, 2S, 2P, 3S and 3P orbitals. Orbitals fill in this order 1S is first 2S is second, then 2P……
  • 16. Filling Electron Orbitals Electron orbitals will fill in this order: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ “1” means first energy level Valence electrons are ONLY in the highest energy level!!
  • 17. Filling Electron Orbitals Electron orbitals will fill in this order: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ “1” means first energy level Valence electrons are ONLY in the highest energy level!! “S” is the type, or shape of the orbital 1S orbital is round
  • 18. Filling Electron Orbitals Electron orbitals will fill in this order: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ “2” is the second energy level Valence electrons are ONLY in the highest energy level!!
  • 19. Filling Electron Orbitals Electron orbitals will fill in this order: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ “2” is the second energy level Valence electrons are ONLY in the highest energy level!! “S” and “P” are the type, or shape of the orbitals 2S orbitals are round 2P orbitals
  • 20. How to Fill Electron Orbitals Example: give me the electron orbital configuration of sodium (Na) 1) We look at the periodic table and see that sodium has 11 electrons 2) Electrons are filled in the following order The 1S 2S and 2P electrons are CORE electrons; they don’t react The 3S (highest energy level) will react; Na has ONE valence electron
  • 21. Remember What We are Doing!! Hydrogen (H) atom We are showing what orbitals electrons are in, and how many are in them. What is the electron orbital configuration of Hydrogen? “n” is the energy level, and corresponds to our electron diagram n=1 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ H: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___
  • 22. Remember What We are Doing!! Hydrogen (H) atom We are showing what orbitals electrons are in, and how many are in them. What is the electron orbital configuration of hydrogen? “n” is the energy level, and corresponds to our electron diagram n=1 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ H: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___
  • 23. Remember What We are Doing!! Hydrogen (H) atom n=1 We are showing what orbitals electrons are in, and how many are in them. What is the electron orbital configuration of carbon? “n” is the energy level, and corresponds to our electron diagram n=2 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ C: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___
  • 24. Remember What We are Doing!! Hydrogen (H) atom n=1 We are showing what orbitals electrons are in, and how many are in them. What is the electron orbital configuration of carbon? “n” is the energy level, and corresponds to our electron diagram n=2 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ C: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___
  • 25. Remember What We are Doing!! Hydrogen (H) atom n=1 We are showing what orbitals electrons are in, and how many are in them. What is the electron orbital configuration of carbon? “n” is the energy level, and corresponds to our electron diagram n=2 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ C: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___
  • 26. Remember What We are Doing!! Hydrogen (H) atom n=1 We are showing what orbitals electrons are in, and how many are in them. What is the electron orbital configuration of carbon? “n” is the energy level, and corresponds to our electron diagram n=2 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ C: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___
  • 27. How to Fill Electron Orbitals Example: give me the electron orbital configuration of neon (Ne) 1) We look at the periodic table and see that neon (Ne) has 10 electrons (electrons = to # of protons) 2) Electrons are filled in the following order Lower level core electrons (level 1 here) DON’T react! Level 2 (highest energy level) will react; Ne has 8 valence electrons!
  • 28. Examples Remember, only the highest level (number) are valence electrons: -Li only has 1 valence electron (2nd level) -Mg only has 2 valence electrons (3rd level) You can see why atoms like Ne are “happy” (=stable) with 8 electrons now; their valence shell is full and they don’t want to give or lose electrons.
  • 29. Questions 20 Points!! 1. What is a valence electron? Draw an atom and show the valence electrons. 2. How many valence electrons do the following elements have: Si, C, O, Ar, K 3. What does inert mean? 4. How many valence electrons do atoms like to have? 5. What do “groups” on the periodic table have in common? 6. Draw the Lewis structure for the following elements: Ne, P, Mg, Na, Pb, Sb 7. Fill out the electron orbitals for the following elements He, Ne, Na, Cl, B, Ar Use the below diagram to guide you: 1S___ 2S___ 2P___ ___ ___ 3S___ 3P___ ___ ___ Bonus question: what element has the following electron configuration? 1s22s22p63s23p64s23d104p65s1