The Structure of Matter Chapter 5 The Structure of Matter

Electron Dot Diagrams Short-hand way to show valence electrons

Steps to drawing Electron Dot Diagrams Write out chemical symbol Find the number of valence electrons Draw the valence electrons in the configuration

Draw electron dot structures for elements 1-18

Compounds 2 or more elements that are chemically combined Examples: H20 NaCl C6H12O6 Held together by chemical bonds Have different properties that the elements that make them up Always has same chemical formula no matter which state of matter

Chemical Bonding

Chemical bonds Ionic Covalent Metallic

Ionic bonding Electrons are gained or lost. One atom gains what another atom has lost. Formed between opposite charged ions Positive metals (cations) and negative nonmetals (anions) Examples: CaCl2 NaCl MgO

Compounds that have ionic bonds: Conduct electricity when dissolved in water (b/c ions are then free to move) Have high melting points MgO

Naming ionic compounds Includes names of all elements that are in the compound Cations (+) uses same name Example: NaCl (sodium chloride) Anion (-) have altered names; drop ending and add “ide” Example: CaCl2 (calcium chloride)

Practice: Name the following ionic compounds. CaF2 KCl BeS K2S MgS CaI2

Writing ionic formulas Identify type of bond that has occurred Identify charges of ions Balance charges using subscripts

Practice: Write the formulas for the following compounds. Sodium flouride Calcium oxide Potassium sulfide Lithium oxide Beryllium chloride Barium phosphide

Covalent bonds Formed between nonmetal atoms Electrons are shared because nonmetals have like charges (both negative) Oxygen

Properties of covalent bonds Low melting points & Do NOT conduct electricity More energy is needed to break triple bond than double, thus it’s stronger.

When electrons are shared equally called nonpolar covalent bonds When atoms aren’t shared equally, they are attracted more to one nucleus than another, polar covalent bond

Naming Covalent compounds 1st element has no prefix, if there is only 1 atom If more than 1, use prefix to tell number of atoms 2nd element – Changes ending to ‘ide’ suffix Prefix tells number of atoms

Name these covalent compounds BF3 N2O4

Write the Formula for the following compounds. Sulfur dioxide Silicon tetriodide Tetraphophorus decoxide Phosphorus trichloride

Polyatomic ions Covalently bonded atoms that have lost or gained electrons They can bond with compounds Example: KNO3 They can bond with other polyatomic ions Example: NH4NO3 Parenthesis show that it acts as one compound Examples: (NH4)2SO4

Practice Writing the Formula Name NaNO3 NaHCO3 (NH4)2SO4

Write the Formulas from the compound name. Sodium nitrate Lithium hydroxide Ammonium chloride Sodium carbonate Potassium phosphate