There are two allotropes of oxygen that exist in the atmosphere: oxygen (O2) and ozone (O3). Oxygen exists as colorless, odorless diatomic molecules and makes up 21% of the air. It is very reactive. Ozone exists as bent triatomic molecules and has different properties depending on its location - it is hazardous near the ground as part of smog but beneficial in the upper atmosphere as it absorbs harmful UV radiation and protects the Earth.

1. I. Oxygen and Ozone

2. Objectives:know the names and formulas of oxygen and ozone.define allotrope.know the structure, properties, and occurrence of oxygen and ozone.

3. I. Oxygen and OzoneThere are two types of oxygen molecules that exist in the earth’s atmosphere: 1. molecules of 2 oxygen atoms – O2 called oxygen 2. molecules of 3 oxygen atoms – O3 called ozone

4. I. Oxygen and OzoneO2 and O3 are allotropes of the element oxygen.allotrope – one of two ore more forms of an element that have the same physical state

5. I. Oxygen and OzoneStructure of oxygen – O2:Most oxygen exists in the form of diatomic molecules (two oxygen atoms double covalently bonded together).Diatomic oxygen molecules have a linear shape.

6. I. Oxygen and Ozone2. Properties of oxygen – O2:Colorless, odorless, and tasteless gas.Oxygen reacts with many metals to form oxides. oxide - ionic compound containing the O-2 ion

7. I. Oxygen and OzoneOccurrence of oxygen – O2:Oxygen makes up approximately 21 % by volume of the air we breathe.Oxygen is the most abundant element by mass in the earth’s crust, waters, and atmosphere. (*Hydrogen is the most abundant element by number of atoms.)

8. I. Oxygen and OzoneStructure of ozone – O3:Ozone molecules consist of 3 oxygen atoms covalently bonded together.Ozone molecules have a bent shape.

9. I. Oxygen and OzoneProperties of ozone – O3:O3 at ground level (bad) - poisonous blue gas with a pungent odor; constituent of smog; harmful to plant tissue and lungs

10. I. Oxygen and OzoneOccurrence of ozone – O3:O3 in the upper atmosphere (good) – ozone molecules absorb harmful uv radiation from the sun; ozone acts as the Earth’s natural sunscreenOver 90% of ozone naturally occurs in the upper atmosphere.The ozone in the upper atmosphere is referred to as the ozone layer.