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-, Al3+, O-2, Mg2+ • 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 Zn2+; fluoride ion F- 11) Cd2+ = 1s22s22p63s23p64s23d104p64d10
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 = ns2np6 Neon: 1s22s22p6 Argon: 1s22s22p63s23p6 Krypton: 1s22s22p63s23p64s23d104p6
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 Al3+ + 3e- • Al (13 e-): 1s22s22p63s23p1 • Al3+(10 e-): 1s22s22p6 = Ne: 1s22s22p6
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-): 1s22s22p63s23p64s23d6 • Fe2+: 1s22s22p63s23p63d6 • Why not lose higher energy e-s in 3d? • Because 4s2 are the valence electrons. Losing them leaves you with a full third valence shell.