Chapter 15 Ionic Bonding

Valence Electrons  Do the electron configuration for the following elements Li Be B O F Ne

Valence Electrons Now look at the outermost electrons by looking at the last s and p orbital Circle and count these electrons These are the valence electrons

Valence electrons – Valence electrons are in the highest energy level of an element’s atom – Valence electrons are the same as group # (roman numeral) for the group A representative elements – Valence electrons are usually the only electrons used in chemical bonds – We use valence e- to write Lewis Dot Structures

Valence electrons (cont.) A. Lewis Dot Structure Ex: bromine Br ●● ●● ● ● ●

Electron configurations for cations & anions A. Octet Rule: when forming compounds atoms want to have 8 electrons (s 2 p 6 ) like the noble gases (except He)

Na (atom) 1s 2 2s 2 2p 6 3s 1 ● lose 1 e - Na (cation) + 1s 2 2s 2 2p 6 octet Using the Dot Structure Na (neutral atom) Na (cation) lose 1 e - + ● Mg (neutral atom) Mg (cation) lose 2 e - 2+ ● metals) Cations (metals) tend to lose electrons, positively charged ion

gain 2e - Cl (neutral atom) O (neutral atom) Cl (atom) 1s 2 2s 2 2p 6 3s 2 3p 5 ● gain 1 e - Cl (chloride ion) - 1s 2 2s 2 2p 6 3s 2 3p 6 octet Using the Dot Structure Cl (chloride ion) - ● O (oxide ion) 2-2- ● ● ● ● ●● ● gain 1 e - ● ● ● ● ● ● ● ● ● ● valence ●● ● ● ● ●● ● ● ● Anions (Nonmetals) have negative charges because they gain electrons

Practice N I Li Ca ● ● ● ● ● N (nitride ion) 3-3- gain 3e - ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● I (iodide ion) gain 1 e - ● ● ● ● ● ● ● ● - ● Li Lose 1 e - + Ca Lose 2e - +2 ● ●

Ionic Compound 1. ionic compounds form crystals 2. high melting and boiling points 3. hard and brittle 4. conduct electricity when dissolved in water or melted A. Properties Composed of a metal (cation) and nonmetal (anion) Ionic bond – oppositely charged ions attract Electrically neutral (+) = (-)

Ionic Bonds Na Cl 1. Sodium and Chlorine ● ●● ● ● ● ● ● donates e - Na + ● Cl ● ● ● ● ● ● ● 2. Potassium and Oxygen K O ● ● ● ● ● ● donates e - K+K+ ● O ● ● ● ● ● ● ● ● + + K ● K+K K2OK2O NaCl +1

Al 3. Aluminum and Bromine Mg N ● ● ● ● ● Mg +2 ● N ● ● ● ● ● ● ● ● + ● -3 ●● ● ● ● ● ● ● Al + 3 ● Br ● ● ● ● ● ● ● + ● ● ●● ● ● ● ● ● ●● ● ● ● ● ● +3 ● Br ● ● ● ● ● ● ● ● ● ● ● ● ● ● ● Mg 4. Magnesium and Nitrogen Mg ● ● ● ● N ● ● ● ● ● Mg +2 ● N ● ● ● ● ● ● ● -3 AlBr 3 Mg 3 N 2

OUTPUT EXAMPLE: 1. Potassium & Fluorine +1 K ● F ●● ● ● ●● + ● K + F ●● ● ● ●● ● ● KF -