1. Unit 5: Chemical Bonding Q: How do atoms interact with each other? Ionization Energy Ions: Cations & Anions

2. The Smallest Atoms Small atoms have more attraction between the positively-charged nucleus and the negative electrons, so the ionization energy is greater in small atoms. –It requires more energy for an electron to be removed from a small atom. Ionization energy: amount of energy needed to remove an electron from an atom.

3. The Largest Atoms In large atoms, valence electrons are far from the nucleus, so there is a weak attraction between the electrons and the (+)-charged nucleus. –Its valence electrons can be easily plucked off. It does not require much energy for electrons to be removed from a large nucleus, yielding LOW ionization energy.

4. Periodicity of Ionization Energy Ionization energies increase across each period because atoms with 8 valence electrons (or close to) have a “tighter grip.” It’s more difficult to remove an electron from an atom with 7 valence electrons than an atom that only has 1 valence electron. Ionization energies decrease down each group. As the size of the atom increases, less energy is required to remove an electron.

5. Removing/Adding Electrons Produce Charged Atoms – IONS! Ionization (removing e-) always produces positively-charged ions, cations. Ion: an atom or group of bonded atoms that has a positive or negative charge

6. Cations: Positive Ions Cations are positive ions. Number of p + > number of e - When an atom loses an electron, they lose one negative charge and become a positive ion. Cations are formed when energy is used to remove an electron (ionization energy)

7. Formation of Cation 11p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Sodium Cation = Na + 11 p + 10 e - ________ 1 + Sodium atom: Na 11 p + 11 e - ______ 0 neutral LOSE one valence electron

8. Anions Negative Ions = Anions Number of p + > number of e - When an atom gains an electron, they gain one negative charge and become a negative ion.

9. Formation of Anions 17p + Chlorine atom Cl 17 p + 17 e - (7 valence e -, 10 core e -) e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- gain one valence electron 17p + e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- e-e- Chlorine anion = negative ion Cl - 17 p + 18 e - _____________________ 1- (8 valence e -, 10 core e -)

10. Li + e e e e Li Lithium atom Lithium ion + Li First Ionization Energy Ionization Energy Ionization energy leads to the formation of positive ions, cations. A + Energy  A + + e -

11. Driving Force Atoms behave in ways to achieve full orbitals. –Full orbitals give the atom the most stability. –Noble gases have the most stability (Except Helium) “Stability” = Lowest energy = Unreactive Octet Rule: Atoms lose, gain, or share electrons in order to have 8 valence electrons.

13. Successive Ionization Energy Unit: Kilojoule (kJ) 1 kJ = 1000 J First ionization energy, I 1 = energy to remove the first electron. Second ionization energy, I 2 = energy to remove another (2 nd ) electron Larger values of IE means that the electron is more tightly bound to the atom and is harder to remove.

14. Successive Ionization Energies (IE) Each successive ionization requires MORE energy than the previous one. A + 1st IE  A + + e - A + + 2nd IE  A 2+ + e - A 2+ + 3rd IE  A 3+ + e - A: Neutral atom Ionization always produces cations.

15. Successive Ionization Energies (KJ/mol) Element H He Li Be B C Al Smoot, Price, Smith, Chemistry A Modern Course 1987, page 190 1 st 1312.1 2372.5 520.3 899.5 800.7 1086.5 577.6 2 nd 5250.7 7298.5 1752.2 2427.2 2352.8 1816.7 3 rd 11815.6 14849.5 3660.0 4620.7 2744.8 4 th 21007.6 25027.0 6223.0 11577.5 5 th 32828.3 37832.4 14831.0 6 th 47279.4 18377.9

16. Successive Ionization Energies (KJ/mol) Al Al + Al 2+ Al 3+ 578 kJ/mol e - 1817 kJ/mol e - 2745 kJ/mol e - The second, third, and fourth ionization energies of aluminum are higher than the first because the inner electrons are more tightly held by the nucleus. 1 st Ionization energy 2 nd Ionization energy 3 rd Ionization energy Smoot, Price, Smith, Chemistry A Modern Course 1987, page 190