Ionic and Metallic Bonding And how!

1/5/12 Objective: To review the fundamentals of ions and learn about ionic bonding Do now: Do the hokey pokey. Turn yourself around. – Then write down what a valence electron is and how many aluminum and gold have. (4 minutes!) Le homework: – Read Ch. 7.1, answer pg 193 # 3-11

Valence electrons The electrons in an atoms highest energy level are called valence electrons – We’ll revisit this later. S and P block: Valence electrons = group # D and F block: all elements have 2 valence e - s

Octet rule Why do atoms give up and receive electrons? BIG IDEA: – Octet rule: atoms give up and receive electrons in order to achieve a full valence shell – A full valence shell has 8 e - s

Cations Metals tend to lose electrons when they form ions –  less electrons than protons –  overall positive charge – Positive ions are called cations

Anions Non-metals tend to gain electrons when they form ions –  more electrons than protons –  overall negative charge – Negative ions are called anions

1/6/12 Objectif: To understand the electron configuration of ions Do now: How many electrons do each of the following ions have? – Na +, F -, Al 3+, O -2, Mg 2+ Do Later: Read 7.2, pg 196 #12 & 13, Pg 199 # 14-22

Hw 1/5/12 3) Valence electrons of rep. element = group # 4) Metals gain electrons, non-metals lose e - s 5) Atoms lose electrons to form cations 6) Atoms gain electrons to form anions 7) a. 1 b. 4 c. 2 d. 6 8) 9) a. lose 2 b. gain 1 c. lose 3 d. gain 2 10) Potassium ion K + ; zinc ion Zn 2+ ; fluoride ion F - 11) Cd 2+ = 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 4d 10

Electron Dot Structures Electron dot structure = chemical symbol of an atom surrounded by dots representing valence electrons. – Ex: Lithium (1 valence e - ) – Zinc (2 valence e - s) – Carbon (4 valence e - s) – Bromine (7 valence e - s)

Noble Gas Configurations Noble gases are in group 8A – 8 valence electrons = full octet – Valence shell = ns 2 np 6 Neon: 1s 2 2s 2 2p 6 Argon: 1s 2 2s 2 2p 6 3s 2 3p 6 Krypton: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6

Noble Gas Configurations Old idea: Atoms gain or lose electrons to form ions with full octets in their valence shell New idea: Atoms with full octets in their valence shell have electron configurations similar to a noble gas. Sodium Neon

Electron configuration of ions How do I write the electron configuration of an ion? – Calculate the number of electrons in the ion – Proceed as usual Example: Al  Al e - – Al (13 e - ): 1s 2 2s 2 2p 6 3s 2 3p 1 – Al 3+ (10 e - ): 1s 2 2s 2 2p 6 = Ne: 1s 2 2s 2 2p 6

Electron configuration of ions Exception: Metals in periods 4 and higher lose electrons from their highest energy levels not their highest energy orbitals. Example: – Iron (26 e - ): 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 – Fe 2+ : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 6 – Why not lose higher energy e - s in 3d? Because 4s 2 are the valence electrons. Losing them leaves you with a full third valence shell.