Warm-Up: Put on Page 14 l Write the electron configuration, orbital diagram, and electron dot diagram for the following elements: 1.Iron 2.Sulfur

Ionic Bonding Follow along in your text Chapter 5 Sections 1 - 3

Valence Electrons are…? l The electrons responsible for the chemical properties of atoms and are those in the outer most energy level. –Core electrons – electrons in the inner energy levels

Keeping Track of Electrons l Atoms in the same group... 1)Have the same outer electron configuration, or layout. 2)Have the same valence electrons. l The number of valence electrons are the same as the group number for an element –Group 2A (Be, Mg, Ca, etc.) have 2 valence electrons

Electron Dot diagrams are… l A way of showing & keeping track of valence electrons. l Write the symbol - it represents the nucleus and inner (core) electrons l Put one dot for each valence electron (8 maximum) l They don’t pair up until there is one on each side (Hund’s rule) X

Electron Dot diagram for Nitrogen l Nitrogen is in Group 15 (5A) so it has 5 valence electrons to show. l First we write the symbol. N l Then add 1 electron at a time to each side. l Now they are forced to pair up. l We have now written the electron dot diagram for Nitrogen.

The Octet Rule l The Octet Rule: atoms form compounds to achieve 8 valence electrons – this is the most stable l Noble gases are unreactive in chemical reactions because they already have 8 valence electrons (except He, which has 2)

Formation of Cations l Metals lose electrons to attain a noble gas configuration. l They make positive ions (cations) l It makes sense to lose electrons because they tend to have only 1, 2, or 3 electrons

Electron Dots For Cations l Metals will have few valence electrons (usually 3 or less); calcium has only 2 valence electrons Ca

Electron Dots For Cations l Metals will have few valence electrons l Metals will lose the valence electrons Ca

Electron Dots For Cations l Metals will have few valence electrons l Metals will lose the valence electrons l Forming positive ions Ca 2+ NO DOTS are now shown for the cation. This is named the “calcium ion”.

Transition Metals l Can lose more than 1 amount of electrons so you must specify –Include the # of electrons lost as roman numerals in the name l Scandium has 3 valance electrons so it can lose 2e - (making it 2+), or lose 3e - (making it 3+) Scandium (II) ion Scandium (III) ion Sc 3+ Sc 2+

Electron Configurations: Anions l Nonmetals gain electrons to attain noble gas configuration. l They make negative ions (anions) l This makes sense because they have 5, 6, or 7 valence electrons and it would be easier to gain 1, 2, or 3 than lose more l Monatomic anions’ names are like the element name but end in -ide

Electron Dots For Anions l Nonmetals will have many valence electrons (usually 5 or more) l They will gain electrons to fill outer shell. P 3- (This is called the “phosphide ion”, and should show dots)

Stable Electron Configurations l All atoms react to try and achieve a noble gas configuration. l 8 valence electrons = already stable! l This is the octet rule (8 in the outer level is particularly stable). Ar

Ionic Bonding l Anions and cations are held together by opposite charges (+ and -) l Ionic compounds are called salts. l Simplest ratio of elements in an ionic compound is called the formula unit. l The bond is formed through the transfer of electrons (lose and gain) l Electrons are transferred to achieve noble gas configuration.

Ionic Compounds Made from a CATION with an ANION (or literally from a metal combining with a nonmetal)

Ionic Bonding NaCl The metal (sodium) tends to lose its one electron from the outer level. The nonmetal (chlorine) needs to gain one more to fill its outer level, and will accept the one electron that sodium is going to lose.

Ionic Bonding Na + Cl - Note: Remember that NO DOTS are now shown for the cation!

Ionic Bonding l All the electrons must be accounted for, and each atom will have a noble gas configuration (which is stable). CaP Lets do an example by combining calcium and phosphorus:

Ionic Bonding CaP

Ionic Bonding Ca 2+ P

Ionic Bonding Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca

Ionic Bonding Ca 2+ P 3- Ca P

Ionic Bonding Ca 2+ P 3- Ca 2+ P

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca 2+ P Ca

Ionic Bonding Ca 2+ P 3- Ca 2+ P 3- Ca 2+

Ionic Bonding = Ca 3 P 2 Formula Unit This is a chemical formula, which shows the kinds and numbers of atoms in the smallest representative particle of the substance. For an ionic compound, the smallest representative particle is called a: Formula Unit

Properties of Ionic Compounds 1.Crystalline solids - a regular repeating arrangement of ions in the solid –Ions are strongly bonded together. –Structure is rigid. 2.High melting points 3.Ionic compounds conduct electricity when dissolved in water

NaCl CsCl TiO 2

The ions are free to move when they are in aqueous solution and thus they are able to conduct the electric current.

Writing Ionic Formulas Mg 2+ l The charge of one ion becomes the subscript of the opposite ion –Called the “Criss-Cross Method” –Use parentheses when adding a subscript to a polyatomic ion –If they are equal and opposite, they will cancel out and you don’t need to show them N 3- = Mg 3 N 2 +

Naming Ionic Compounds l Combine the names of the ions – always put cations first. Al 3+ Aluminum SO 4 2- Sulfate Al 2 (SO 4 ) 3 Aluminum Sulfate