8/25/2011

1

Living organisms are composed of

about 25 chemical elements

Most Common Elements

In the Human Body (96%)

Essential Trace Elements

In the Human Body (0.01%)

Trace elements are common additives

to food and water

8/25/2011

2

Elements can combine to form

compounds

Atoms consist of protons, neutrons,

and electrons

Isotopes

• Carbon-12: Protons-6 Neutrons-6 Electrons-6

• Carbon-13: Protons-6 Neutrons-7 Electrons-6

• Carbon-14: Protons-6 Neutrons-8 Electrons-6

Carbon Will

Always Have 6

Protons

Only The Number

Of Neutrons

Change in

Isotopes!

8/25/2011

3

Radioactive isotopes can help or harm

us

Electron arrangement determines the

chemical properties of an atom

Ionic bonds are attractions between

ions of opposite charge

8/25/2011

4

Covalent bonds join atoms into

molecules through electron sharing

Unequal electron sharing creates polar

molecules

Hydrogen bonds are weak bonds

important in the chemistry of life

Partial Positive End

Partial Negative End

8/25/2011

5

Hydrogen bonds make liquid water

cohesive

Waters hydrogen bonds moderate

temperature

Ice is less dense than liquid water

8/25/2011

6

Water is the solvent of life

The chemistry of life is sensitive to

acidic and basic solutions

Acidic Solutions

have A High

Concentration of

H+ Ions

Neutral Solutions

have equal

concentrations

of H+ and OH-

IonsBasic Solutions

have a low

concentration on

H+ Ions

The search for extraterrestrial life

centers on the search for water

8/25/2011

7

Chemical reactions make and break bonds,

changing the composition of matter