Chapter 5.4, 6.3, 6.4, IONS AND IONIC COMPOUNDS

Ions – Charged atoms »Either positive or Negative Anions – negative charge »________________________________ Cations – positive charge »________________________________ Recap of Key Words

Chemical Reactivity Some elements are more reactive than others. How much an element reacts depends on the electron configuration. The noble gases are the least reactive. Which do you think are the most reactive? –Non-metals-_________________ –Metals-_________________

Why Bond? Atoms bond to increase stability. Which electrons determine stability? –Stability is based on valence electrons. What is the definition of a chemical bond –A chemical bond is a force that holds two atoms together and makes them behave like a unit.

Group 1: 1 Group 2: 2 Group 13: 3 Group 14: 4 Group 15: 5 Group 16: 6 Group 17: 7 Valence electrons Recap How many valence electrons are the elements trying to achieve? 8

Noble gas configuration Noble gases are the –most stable elements –because of their valence electrons. Except for helium, –they all have 8 –2 in the s, 6 in the p valence e - He 2 Ne 8 Ar 8 Kr 8 Xe 8 Rn 8 valence e - He 2 Ne 8 Ar 8 Kr 8 Xe 8 Rn 8

Octet Rule John Newland recognized a pattern and called it the law of octaves, now we can take this a step further A concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty or full valence shells of eight electrons..

The Octet Rule Atoms are most stable if they have a filled outer shell of ___ electrons. an octet.Except for H and He, a filled shell contains 8 electrons - an octet. Atoms will gain or lose share gain or lose (ionic compounds) share (covalent compounds) electrons to make a filled outer shell.

Charges to Find on Periodic Table Atoms Gain or Lose electrons to form stable ions.

Cations and Anions Cation: a positively charged ion –Metals typically form cations by LOSING electrons Example: Na +1 (lost one electron) Anion: negatively charged ions Nonmetals typically form anions by GAINING electrons Example: Cl -1 (gained one electron)

Transition metals There are some d and p block metals that only make one ion. All Group 5: Ni, Zn, Cd: Ag: Lanthanides and actinides: All Group 5:+3 Ni, Zn, Cd:+2 Ag:+1 Lanthanides and actinides: +3

Ions and the octet rule Ions: Atoms that have gained or lost electrons to obey the octet rule. Na [Ne]3s 1 e - + Cl [Ne]3s 1 3p 5

The Formation of NaCl Na + Cl The electron from Na moves over to the Cl. Now both satisfy the octet rule. Na becomes Na +1 - a cation Cl becomesCl -1 - an anion The + and - charges attract each other and form an ionic bond. +1

NaCl

To make an ionic bond, the following must take place. 1. Metal atom(s) must donate valence electrons to nonmetal atom(s). 2. This electron exchange creates cations and anions. 3. Opposites attract! = ionic bond

Facts about Ionic Compounds 1.The ratio of cations to anions in an ionic bond has NO overall charge. 2.Ionic bonds are strong. 3.Have distinctive properties (high boiling and melting points) 4.Conduct electric current. 5.Hard and brittle.

Structure of an ionic compound

Structure of an ionic compound

Using what you know about the crystal structure of ionic compounds, explain why they would be brittle. Use pictures if necessary (I did).

Which solution is ionic?

Lattice energy The higher the lattice energy, the stronger the attraction between ions. Lattice energy Compound kJ/mol LiCl834 NaCl769 KCl701 NaBr732 Na 2 O 2481 Na 2 S 2192 MgCl MgO 3795 Lattice energy Compound kJ/mol LiCl834 NaCl769 KCl701 NaBr732 Na 2 O 2481 Na 2 S 2192 MgCl MgO 3795 energy released when ionic bonds are formed

How do I write the name of a binary compound? NaCl Sodium chloride CaBr 2 Calcium bromide KI _____________________________________ Li 3 N _____________________________________ BaS_____________________ 1) The cation is always written first; the anion is written second. 2) The name of the metal stays the same. 3) The anion changes to an –ide ending. 4) Subscripts are not included in the name. RULES:

Writing the Formulas for Binary Ionic Compounds: The Criss Cross Method RULES 1)You must determine the charge of the cation (for d- block elements, indicated by Roman numerals) and anion. (using the octet rule) 2)The charge of the cation crisscrosses with the charge of the anion. Both charges become subscripts WITHOUT the +/- written with the subscript.

Writing the Formulas for Binary Ionic Compounds: The Criss Cross Method Try these: –Sodium sulfide –Calcium oxide Like in algebra, if there is a 1 with the ‘x’, you don’t have to write it. If the subscript is 1, you don’t have to write it. If the subscripts are the same, you don’t have to write them.