The Chemical Basis of Life

Objectives:

• Explain the relationship between elements, compounds, atoms, and molecules

• List the major elements and major minerals• Discuss atomic structure and explain how

an atom’s electron shells influence its ability to enter into chemical reactions

Objectives

• Compare and Contrast the three major types of chemical bonds

• List and describe the three basic types of chemical reactions that occur in living material

Terms

• Biochemistry- chemistry that deals with living organisms

• Matter- anything that occupies space and has mass

• Elements- can’t be broken down into tow or more different substances–EX: O2

Terms

• Compound- two or more elements together–EX: CO2 or NaCl

• Major elements- make up a large portion of our body

• Trace elements- are present in the body in small amounts

Chemical Symbols

• O- oxygen

• C- carbon

• H- Hydrogen

• N- Nitrogen

• Ca- Calcium

• P- Phosphorus

• K- Potassium

• S- Sulfur

• Na- Sodium

• Cl- Clorine

• Fe- Iron

• I- Iodine

Atoms

• basic building block of all things

• can be broken down into subatomic particles

Atomic Structure

• Protons

–positive

–found in the nucleus

• Neutrons

–neutral

–found in the nucleus

Atomic Structure

• Electrons

–negative

–found in the electron shell

Atomic Number and Weight

• Atomic number- the number of protons in a nucleus

• Atomic weight- mass of an atom

– only the nucleus has weight

– equals the number of protons and neutrons

Electron Shells

• The number of electrons equals the number of protons

• use the Bohr model to visualize electrons

Bohr Model

• Each ring is different energy level

• First shell holds two• Second shell holds 8• If outer shell is full,

the atom won’t form bonds

Bohr Model

• Rule of Octet- says the outer shell can hold eight electrons

Isotopes

• All atoms of the same element have the same number of protons

• They do not contain the same number of neutrons and these are called isotopes

• Ex: Most carbon has 6 electrons but carbon 14 has 8– atomic weight of 14

Chemical Bonds

• Molecule- any two or more atoms coming together– N2

• Compound- two or more different atoms come together– NaCl

Ionic or Electrovalent Bonds

• Forms by the transfer of electrons

• occurs as a result of electrically charged atoms called ions

Ionic Bonds

Na needs to lose one, Cl needs to gain one

Covalent Bonds

Shares Electrons

Hydrogen Bond

• Form due to unequal charge

• no electrons are shared or transferred

• Water is a hydrogen bond

• Are very weak

• Allows water to change states

Chemical Reactions

• Synthesis- putting things together

– A + B = AB

• Decomposition- take things apart

– AB= A + B

• Exchange

– AB + CD = AC + BD