Compounds Chapter 3 Section 2

Compounds A pure substance created when two or more elements chemically combine(react) Ex: Magnesium + Oxygen  Magnesium Oxide The compounds are different from the elements that make them up

Mg + O

More Examples of Compounds Water: H and O  H 2 0 Salt: Na and Cl  NaCl Sugar: C and H and O  C 6 H 12 O 6 Carbon Dioxide: C and O  CO 2.

COMPOUNDS Elements combine in definite ratios – They are not random combinations – They combine based upon the elements masses

How they combine… In order for a compound to form, the elements must REACT and undergo a chemical change. Once they combine, they have different properties because they are a totally different substance. Examples: C + O 2 CO 2 2H 2 + O 2 2H 2 O

Unique Properties of Compounds Like elements, compounds have their own physical properties. – Ex: Melting points, boiling points, etc Compounds can also be identified by chemical properties. – Ex: React with acids, react with water, react with light, etc.

Breaking Down Compounds Compounds can be broken down. Some compounds can be broken into the elements that make them up. This can only be done by chemical means. – Ex: Heating, electricity Compounds can not be broken down by physical means. – Ex: You can not filter water to get H and O You can not ground salt to get Na and Cl

Bohr Model of Water Bohr Model of Water (H 2 O) Covalent

Bohr Models and Compounds Bohr Model of Water (H 2 O) 1 P 0 N 1 P 0 N 8 P 8 N

Bohr Model of Salt Sodium Chloride (NaCl) Ionic

Bohr Model of Salt (NaCl) Bohr Models and Compounds

Na + Cl  NaCl

Class Assignment Review over pages Demo Mg + 0 Try and draw the Bohr Model of CO 2