Chemical Bonding

Determined by difference in Electronegativity. Bonding types Ionic Covalent Metallic Determined by difference in Electronegativity.

- Ions + charged atoms (gained or lost e-) Formed from ve- only (group A #) Cations- formed when a metal atom loses e- forming a + ion Anion – formed when a nonmetal atom gains e- to form a - ion + -

Ionic compounds Crystalline solids (made of ions) High melting and boiling points Conduct electricity Many soluble in water but not nonpolar liquid

Positive and negative IONS Attraction between positive and negative.

Positive and negative IONS Becomes brittle when the like charges line up and repel.

Ionic

Writing Formulas and Naming Ionic Compounds RULES: Write the symbol and charge of the cation (+ charged metal or hydrogen) Write the symbol and charge of the anion (- charged nonmetal) Check the charges  they must = 0

Binary Ionic Compounds (2 atoms: metal & nonmetal) sodium + iodine Na +1 + I -1 calcium + oxygen Ca+2 + O-2 potassium + sulfur K+1 + S-2 (4) aluminum + oxygen Al+3 + O-2 (5) Chlorine + magnesium Mg+2 + Cl-1 NaI CaO K2S Al2O3 MgCl2

Binary Ionic Compounds (2 atoms: metal & nonmetal) sodium + iodine Na +1 + I -1 calcium + oxygen Ca+2 + O-2 potassium + sulfur K+1 + S-2 (4) aluminum + oxygen Al+3 + O-2 (5) magnesium + chlorine Mg+2 + Cl-1 Sodium iodide NaI calcium oxide CaO potassium sulfide K2S aluminum oxide Al2O3 magnesium chloride MgCl2

Binary Ionic Compounds Practice Write formula and name each 1. chlorine + hydrogen 6. lithium + oxygen 2. calcium + sulfur 7. bromine + sodium 3. selenium + aluminum 8. potassium + sulfur 4. barium + fluorine 9. iodine + lithium iodine + magnesium 10. strontium + chlorine

Covalent Bonds Sharing of ve- between 2 or more atoms molecule – smallest chemical unit of a substance capable of a stable independent existence

includes: types & #s of atoms Covalent molecules are represented with a molecular formula – representation of actual composition of a covalent molecule includes: types & #s of atoms ex: H20 (water); O2 (oxygen); C12H22O11 (table sugar)

Diatomic molecules Element Molecular formula Hydrogen H2 Nitrogen N2 2 atoms of the same element covalently bonded; there are only seven Element Molecular formula Hydrogen H2 Nitrogen N2 Oxygen O2 Fluorine F2 Chlorine Cl2 Bromine Br2 Iodine I2

Characteristics of Covalent Molecules Usually liquids or gases at room temperature Low melting and boiling points Nonelectrolytes – do not conduct electricity

Nonpolar covalent equal sharing of e-

Polar Covalent unequal sharing of e- 1 atom pulls e- stronger/harder Results in a molecule with partially positive and negative regions

Binary covalent Molecules 2 element share e- Naming Rules: 1st word – use name of element *use element with lowest electronegativity 2nd word – ALWAYS use prefix to indicate the # of 2nd element (use the ending –ide)

drop the “a” or “o” of the prefix if the root word begins with a vowel EX: penta-  pentoxide mono-  monoxide

Naming Hydrates Prefix Number mono- 1 di- 2 tri - 3 tetra- 4 penta- 5 hexa- 6 hepta- 7 octa- 8 nona- 9 deca - 10 Naming Hydrates

Binary Covalent Compounds SiO2 silicon dioxide S2O4 disulfur tetroxide CF4 carbon tetrafluoride PCl3 phosphorus trichloride

Writing formulas rules: Write the symbol of the 1st element and number for the prefix (use a subscript) Write the symbol of the 2nd element and number for the prefix (use a subscript)

Practice: Carbon dioxide CO2 Tetranitrogen difluoride N4F2 Diphosphorus trioxide P2O3 Dihydrogen monoxide H2O

Metallic Bonding

Metallic Bonds bonds between metals metallic atoms have loosely held electrons

electrons are more or less free to move from one atom to another. metal ions floating in a “sea of mobile electrons” around a positive nucleus

Metallic Bonds results in the formation of alloys not compounds metal atoms do not combine in fixed ratio

Properties of Metallic Bonds Good conductors Ductile Malleable Have luster (shiny) High melting point Solid (hard) at room temperature Alloys: homogeneous mixture of metals (ex. steel, bronze, brass, pewter)

Some common alloys

Intra vs inter Intramolecular forces. within a molecule Intra vs inter Intramolecular forces within a molecule “Atom to Atom” Intermolecular forces “Molecule to Molecule”

Without these forces there would be no liquids or solids Without these forces there would be no liquids or solids. Everything would be a gas.

Intermolecular Forces 1) London Dispersion forces Intermolecular Forces 1) London Dispersion forces very weak attraction between electron clusters in Noble gases and nonpolar molecules. There is nothing else holding them together.

London Dispersion forces

2) Dipole-Dipole forces Attraction between positive and negative areas of different molecules.

Like Dissolves Like sodium chloride (Polar) dissolved in Water (Polar)

3. Hydrogen Bonding. due to polarity. Positive Hydrogen end 3. Hydrogen Bonding due to polarity Positive Hydrogen end attracted to Negative area of another molecule

Hydrogen Bonding in DNA

4. Electrostatic bonding Ionic Bonding!!!!!