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Ionization Energy Trends

4f. 5f. Ionization Energy Trends. Electronegativity. Increasing Electronegativity. Decreasing Electronegativity. Lewis Structure Assumptions. Only valance electrons are involved in bonding. Atoms react to form molecules, so to achieve stable noble gas electron configurations.

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Ionization Energy Trends

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  1. 4f 5f

  2. Ionization Energy Trends

  3. Electronegativity Increasing Electronegativity Decreasing Electronegativity

  4. Lewis Structure Assumptions • Only valance electrons are involved in bonding. • Atoms react to form molecules, so to achieve stable noble gas electron configurations. • Atoms in molecules want eight valance electrons (octet rule) except for hydrogen which wants two electrons (duet rule). • In covalent compounds atoms share electrons to form bonds in order to achieve stable noble gas electron configurations. In ionic compounds electrons are transferred from one atom to another to achieve stable noble gas electron configurations.

  5. Rules for Drawing Lewis Structures Step 1: Count the total number of valance electrons. Step 2: Identify the central atom (the first atom written unless that atom is hydrogen). Place all terminal atoms around that atom. Hydrogen atoms NEVER have more than one bond. Step 3: Complete the octet for all atoms in the Lewis structure with lone pairs of electrons (except hydrogen). Step 4: Check your structure by counting the number of valance electrons used (they will match step 1 if the structure is correct). If your valance electrons don’t match you will need to tweak your structure as follows.

  6. Tweaking Lewis Structures Too Many Electrons Initially: Redraw the Lewis structure from step 2 adding a double bond. If you still have too many electrons add another multiple bond and repeat. Always add double bonds before triple bonds. Every double bonds effectively remove two electrons from the structure while triple bonds effectively remove 4 electrons.

  7. “Exceptions” to the Octect Two Few Electrons: If you only have four or six valance electrons initially you can’t possibly fill the octet rule (usually BeH2 or BH3). Just place hydrogens around central atoms and call it done.

  8. “Exceptions” to the Octect Odd number of electrons: One atom will have to have less than eight electrons. Draw the Lewis structure as if it had one more valance electrons than it actually does. Then subtract one electron from the least electronegative element (often the central atom).

  9. “Exceptions” to the Octect Exceeding the Octet Rule: If the central atom is in the third row or below it may be possible to exceed eight electrons around the central atom. But only if you absolutely have no choice. If you can give everything eight and only eight do that first. When you must break the octet rule draw the structure as you would in steps 1-4 and the place the extra electrons around the central atom. Even when breaking the octet rule no atom will ever have more than 12 electrons.

  10. Organic Lewis Structure Rules • Based on formal charge arguments

  11. p-orbitals are 90 degrees from each other

  12. 1 s + 3 p = 4 sp3 orbitals

  13. 1 s + 2 p = 3 sp2 orbitals

  14. 1 s + 1 p = 2 sp orbitals

  15. Unhybridized p-orbitals delocalize the -electrons

  16. ALL atoms are sp2 hybridized in NO31-. There are NO sp3 hybridized orbitals.

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