Unit 3.3 “Elements & Compounds” Mr. Ivey

Substances are either: a) elements, or b) compounds

Elements Compounds -simplest kind of matter Can’t be broken down any simpler and still have properties of that element! all 1 kind of atom. substances can be broken down only by chemical methods when broken down, the pieces have ∆ properties than the original compound. made of 2 or > atoms, chemically combined (not just a physical blend!) Elements Compounds

e.g. of elements Sodium - Na solid, silver, play doughy element reacts violently w/water

e.g. of elements Chlorine - Cl Green gas Lethal if inhaled Kills bacteria 99%

e.g. of compounds Sodium Chloride - NaCl Solid, white crystalline powder Used for flavoring food

e.g. of elements Carbon - C Solid, Black (charcoal) not particularly harmful

e.g. of elements Oxygen – O (usually expressed O2) Odorless, clear, gas not harmful, but explosive around a flame

e.g. of compounds Carbon Dioxide – CO2 Odorless, clear gas deadly if inhaled in large quantities

e.g. of elements Hydrogen – H (usually expressed H2) Colorless, Odorless flammable gas Highly reactive, therefore harmful

e.g. of elements Fluorine – F (usually expressed F2) Pale Yellow, Odorless gas Highly toxic gas

e.g. of elements Fluoride – (usually expressed F- ion) Fluorite (rock) source of fluorine & fluoride Fluoridation of water to prevent tooth decay

e.g. of compounds Hydrogen Fluoride – HF Clear, irritating gas Creates HF acid causes blindness and death

Compound vs. Mixture Compound Mixture Made of one kind of material Made of more than one kind of material Made by a chemical change physical change Definite composition Variable

Which is it? Compound Mixture Element

Elements vs. Compounds cannot be broken down Compounds Elements Chemical Change can be broken down into simpler substances by chemical means, but ... cannot be broken down ∆ that produces matter with a different composition than the original matter.

Properties of Compounds Different properties than their component elements. Due to a CHEMICAL CHANGE, the resulting compound has new and different properties: Table sugar – carbon, hydrogen, oxygen Sodium chloride – sodium, chlorine Water – hydrogen, oxygen

Classification of Matter

Symbols & Formulas 117 elements Elements Compounds have a 1 or two letter symbol first letter always capitalized; if there is a second letter, it is written lowercase: B, Ba, C, Ca, H, He have a formula. Start learning the elements names and symbols listed in your Periodic Table