Elements and Compounds

Pure substances Have only one type of particle Same composition throughout

2 groups: Elements Compounds

Elements Cannot be separated by physical or chemical means 92 elements (naturally occurring) Classified by properties

Unique Characteristic Properties of Elements Melting point, Boiling point Density, Conductivity (heat and electricity) Reactivity, etc

Look @ Fig.3 p83 Can you tell the 3 elements apart using… 1. density?

What about … 2. Conductivity? 3. Reactivity? 4. Melting Point?

A Substance is identified by A set of properties not any one single property

Three groups of elements have shared properties: Metals (most elements) Nonmetals Metalloids

Metals … Shiny Good conductors Malleable Ductile Have high melting & boiling points

Examples of metals Found on the left side of the Periodic Table Most are solids except for Hg

Nonmetals Dull Poor conductors Brittle, unmalleable, not ductile Lower Melting and Boiling points, Densities.

Metalloids Only 7 of them Show properties of both metals and nonmetals: some shiny, some dull; somewhat malleable, ductile, etc. Semi-conductors

The Metalloids Boron Germanium Silicon Arsenic Antimony Tellerium Polonium

Quiz Identify group(s) of elements that have following properties: metals, nonmetals or metalloids Good conductors of electricity Brittle and unmalleable

Shiny Poor conductors of thermal energy

Compare Metals and Non Metals

Review Do Review What is a pure substance?

Assignment: Use a Periodic Table pR12-13 to fill in this table in your notebook: Fill in the first 20 elements then add the ff 15 more … Atomic Number Element Name Chemical Symbol 1 Hydrogen H 2

Iron, Cobalt, Nickel, Copper, Zinc, Silver, Tin, Gold, Lead, Mercury, Iodine, Bromine, Lanthanum, Actinium, Uranuim

Symbols derived from Latin names of elements English name of the element Symbol Latin name of the element Copper Gold Iron Lead Mercury Potassium Silver Sodium Tin Tungsten Cu Au Fe Pb Hg K Ag Na Sn W Cuprum Aurum Ferrum Plumbsum Hydrargysum Kalium Argentum Natrium Stannum Wolfarm

Metal/Nonmetal/Metalloid? Mini-project Create Flashcards of each element Get a ring or Ziploc bag or Make a booklet http://periodictable.com/ Element Chemical symbol Atomic Number State at R.T. Metal/Nonmetal/Metalloid?

The 2nd type of pure substance Section 4-2 Compounds The 2nd type of pure substance

Two or more elements chemically combined Atoms combine in specific ratios They CAN be broken down by chemical means (Water into hydrogen and oxygen)

Compounds to know (out of nearly 4 million kinds) Table salt, water, carbon dioxide, glucose, baking soda (FORMULAS?)

A Chemical Formula Symbols used to identify elements present Tells ratio of element atoms present Is constant for a particular compound

Chemical Formulas: H2O H2O2 2 : 1 2 : 2 CO2 H2SO4 1 : 2 2 : 1 : 4

Mass Ratio is constant 2g : 16g 18g 1g : 8g Ratio: 1:8 Hydrogen + Oxygen Water 2g : 16g 18g 1g : 8g Ratio: 1:8

Mg + O MgO 12g : 8g Ratio- 3:2 CAN be broken down by chemical means e.g.(Water into hydrogen and oxygen)

Properties: Each compound has its own unique set Physical Properties … Chemical properties … Different from the elements that formed it e.g. O, H : colorless, odorless gases H2O : liquid. Na -metal, Cl -green gas, poisonous Sodium chloride- salt, colorless, essential for health.

Law of Conservation of Matter Matter is neither created nor destroyed; It only changes from one form to another

Compds are classified by: Their pH – How acidic or basic they are If Organic (Carbon-containing) or Inorganic The role they play - Proteins – enzymes, structural - Carbohydrates - Lipids – fats & oils - Nucleic acids

For more info… Visit this photogallery of the elements http://chemistry.about.com/od/periodictableelements/ig/Element-Photo-Gallery.--98/