In the Air , In the Crust,

In the Water.

Elements on Planet Earth

Background• Our understanding of the elements has

progressed from the Fire, Air, Earth, Water stage to the current theory that everything is composed of atoms.

Elements In the Atmosphere

• In the atmosphere there are a number of elements.

• These are – Nitrogen 78.03 %– Oxygen 20.99 %– Argon 0.94 %– CO2 0.04 %

Surprised?

Elements In the Atmosphere

• Oxygen is so reactive it cannot exist for more than a moment as an uncombined atom. It combines to form O2

• This is called a diatomic molecule• Nitrogen is essential to all life. It is also a

diatomic molecule.• Let’s look at Nitrogen…

Nitrogen In the Atmosphere• Nitrogen is an element• It’s symbol is N• The smallest particle of nitrogen is the

nitrogen atom - N• Nitrogen exists in the atmosphere as a diatomic

molecule - N2

• There are other elements in the atmosphere– H2O , H2S

CO2 In the Atmosphere• In the 17th century people began to burn coal

to heat houses and provide energy for commercial use.

• In the 19th century we began to burn petroleum fro cars and industry.

• The result has been an increase in the amount of CO2 in the atmosphere.

• Increased CO2 is predicted to cause global warming.– How will warming affect the earth?

The Hydrosphere

• Many elements are locked in compounds.

• One of the most important compounds is H20.

• Water is essential for life and is a solvent for many other substances.

• Most compounds are soluble in water.

• All of the water in the hydrosphere contains dissolved compounds.

The Hydrosphere

• Animals living in water depend on dissolved O2 to breathe

• Plants that live in water depend on dissolved CO2 to breathe

• Sea water contains NaCl , KCl and CaCl2

• These compounds come from rocks and soil that have been washed into solution by rain.

The Crust

• There are many elements in the Earth’s crust

• Some - Au, Ag, C - are found as elements. Others are found combined as compounds.

• Elements that are stable can be found as atoms of pure substance.

• Atoms that are very reactive are found as parts of compounds.

Cycling The Elements

• Elements and compounds cycle through the atmosphere, hydrosphere and crust.

• This prevents a buildup of elements in a particular part of the Earth.

• Life on Earth needs this cycling– CO2 to O2 + C– Nitrogen

• Photosynthesis and respiration make use of the elements hydrogen, oxygen and carbon, cycling them through the atmosphere.

Photosynthesis and Respiration

• Respiration: what animals doGlucose + oxygen --> carbon dioxide + water + energyOrC6H1206 + 6 O2 -----------> 6 CO + 6 H2O + ENERGY

• Photosynthesis: what plants doSunlight + carbon dioxide + water --> glucose + oxygenOr6 CO + 6 H2O + ENERGY -----> C6H1206 + 6 O2

Metals

Metals

• All elements can be classified as metals , non-metals or metalloids.

• Metals comprise the majority of the elements.

• Metals have a characteristic set of properties.

Metals

• Metals …– can be moulded into shapes (malleable)– can be formed into thin wires (ductile)– conductors or heat and electricity (conductivity)– have characteristic lustre or sheen– High melting and boiling point (except mercury)

Non-metals

• Non-metals …– Are usually brittle.– Are poor conductors of heat and electricity.– Have a dull surface (solids)– Have lower melting and boiling points - often gaseous

at room temperature.

Metalloids

• Metalloids have some metal and some non-metal properties. They are usually– Solid at room temperature with high boiling temps

– Good thermal insulators

– Brittle and non-ductile

– May or may not be good conductors of electricity.

In the Periodic Table• Metals are found on the left side of the table

with the most active metal in the lower left corner.

• Nonmetals are found on the right side with the most active nonmetal in the upper right hand corner of the chart.

• Since the most active metals react with water to form bases, the Group I metals are called alkali metals.

• Elements found along the dark line in the periodic table are called metalloids. They are the elements which have certain characteristics of metals and other characteristics of nonmetals.

• Some examples of metalloids are boron, silicon, arsenic, and tellurium.