CHEMICAL BONDING

1. CHEMICAL BONDING Ionic Bonding Covalent Bonding Metallic Bonding

2. What is bonding? Joining of atoms to make compounds and molecules. • Become more stable - lower potential energy - Fill valence shell (Octet Rule) Ionic Bonds Covalent Bonds

3. Electronegativity Attraction of the bonded electrons to one of the atoms. A B But… which atom?

4. The one with the highest electronegativity! Electronegativity Trend Same as electron affinity and ionization energy.

5. Forms of Chemical Bonds • There are 2 extreme forms of connecting or bonding atoms: • Ionic: completetransfer of electrons • Covalent: electrons equally shared Most bonds are somewhere in between.

6. Bond Type = Difference in electronegativities Greater than 1.7 = Ionic Bond 1.7 - .3= Polar Covalent Bond .3 – 0= Non Polar Covalent Bond SUBTRACT!

7. Practice • What type of bond exists between sodium and oxygen? IONIC BOND 3.5 – 0.9 = 2.6 Greater than 1.7 = Ionic 1.7 or less = Covalent

8. Bond type is on sliding scale of ionic & covalent bond extremes known as % ionic character. Pure Covalent Bond 1.7 (50%) Electroneg. Difference Ionic Bond

9. Major Types of Bonding METALLIC BONDING IONIC BONDING COVALENT BONDING

10. Substances with Metallic, Ionic, and Covalent Bonds

11. ELECTRON DOTS & IONS For atoms to enter into chemical reactions and become more stable, electrons are lost or gained and IONS are formed. Atoms will gain or lose electrons from the principal quantum level in order to achieve a noble gas configuration. With the exception of helium, 8 electrons in the outer energy level make an element stable and unreactive. This is the OCTET RULE.

12. Electron Dot Structures • A visual way to show the valence electrons • Follow the orbital filling rules. • Example: Sulfur S electrons Electron Configuration: 1s22s22p63s23p4 S pz electrons px electrons py electrons

13. You Try! Write structures for H, Mg, N, Cl, Ne H N Mg Cl Ne

14. IONS Atoms that have gained or lost electrons and are no longer neutral. Atoms gain or lose electrons to become more stable (lower potential energy). They become like a noble gas configuration. Follows Octet Rule!

15. IONS Electron Configuration: 1s22s22p63s1 Na Examples: Sodium Choice… Lose 1 electron and drop to full 2nd energy level or…. Gain 7 electrons to get a full 3rd energy level? But: (+)11 protons (-) 10 electrons (+) 1 +1 Na New electron configuration: 1s22s22p6 (Like Neon)

16. IONS Electron Configuration: 1s22s22p63s23p4 S Examples: Sulfur Choice… Lose 6 electrons and drop to full 2nd energy level or…. Gain 2 electrons to get a full 3rd energy level? But: (+)16 protons (-) 18 electrons (-) 2 -2 S New electron configuration: 1s22s22p63s23p6(Like Argon)

17. Ionic Bonding • Ionic bonding involves the electrostatic force of attraction of a cation (+) and an anion (-). • Charges and amounts of atoms balance to become a neutral compound.

18. Forms Crystals • Regular geometric patterns of the formula unit. (lattice structure) • Formula unit is simplest whole number unit.

19. Lewis Dot Diagrams for Ionic Bonding Mg2+ + 2 Br  MgBr2

20. Parts of an Equation REACTANTSOXIDATION NUMBER PRODUCTSCOEFFICIENT SUBSCRIPT Mg2+ + 2 Br  MgBr2 *Cation is always written first! *Atoms combine in simplest whole number ratios to make their charges zero.

21. You Try! Write the Lewis dot equation showing the ionic bonding between oxygenandsodium. 2Na+ + Br  Na2O

22. OXIDATION • Process of an element becoming more POSITIVE. • Could occur from neutral to +1 or from +1 to +2. • How does element oxidize? • Loss of electrons! Example: Na0Na1++ 1e- The ionic charge of Na (0 or 1+) can also be called its oxidation number.

23. REDUCTION • Process of an element becoming more NEGATIVE. • Could occur from neutral to -1 or from -1 to -2. • How does element reduce? • Gain of electrons! Example: O0 + 2e-O2- What’s the oxidation number for O?

24. PRACTICE Write the oxidation number (ionic symbols) of the following elements: Ba, I, Br, Be Write oxidation / reduction equations for aluminum and oxygen forming ions. Write the Lewis dot equation combining aluminum and oxygen.

25. Naming Ionic Compounds Terms Monatomic ion Na1+or O2- Polyatomic ion NO31-NH4+ oxyanion– polyatomic w/ Oxygen Binary Ionic Compound Na2O Ternary Ionic Compound NaNO3 IUPAC: International Union of Pure and Applied Chemistry

26. Basic Rules • Net ionic charge is zero: MgO BaCl2 Al2O3 • An –ide ending generally indicates a binary compound: sodium chloride • An –ite or –ate ending usually means there is a polyatomic anion: sodium chlorate NaClO3 • Use parenthesis for multiple polyatomic ions (other than 1). Barium chlorate Ba(ClO3)2 • Roman numeral shows ionic charge of the transition metal cation. Iron (III) chlorateFe(ClO3)3 • *this also includes metals up to the step-line with exceptions of Al+3, Zn+2, Ag+1, Cd+2 • ZnCl2 zinc chloride

27. Examples • Write the name of the following compounds: • Na2O ___________________________ • Cu3N2 ___________________________ • PbO ___________________________ • SnO2 ___________________________ • Na2CO3 ___________________________ • Mg(ClO2)2 ___________________________ sodium oxide copper (II) nitride lead (II) oxide tin (IV) oxide sodium carbonate magnesium chlorite

28. Examples • Write the formula for the following compounds: sodium oxide _______________ tin (IV) chloride ________________ nickel (II) phosphide _____________ ammonium hydroxide _____________ magnesium acetate________________ Na2O SnCl4 Ni3P2 NH4OH Mg(C2H3O2)2