Chapter 2

Remember…..

Organism

organ system

Organs

Tissues

Cells

Molecules

atoms

Matter = anything that

1. has mass

2. takes up space

3 Forms of Matter

Holds Shape

Fixed volume

Container shape

Free Surface

Fixed Volume

Container Shape

Volume of Container

Matter composed of basic substances

Elements1. Specific chemical & physical characteristics

2. Fundamental substances

3. 1 type of atom

92 naturally occurring elements

11+ Synthetic elements

Primary Elements of Living Things

1. Carbon

2. Hydrogen

3. Nitrogen

4. Oxygen

5. Phosphorus

6. Sulfur

98% 95%

Naming of Elements1. Latin or English

2. Atomic Symbol = 1 or 2 letter abbreviation

Carbon = C

Hydrogen = H

Oxygen = O

Sodium = Na

Iron = FePotassium = KNitrogen = N

Atom = smallest particle of an element

that displays properties of that element

John Dalton: Atomic Theory

Early 1800’s

“All Matter is composed of atoms”

Structure of an Atom: (Sub-atomical Particles)

Protons

Neutrons

Electrons

Sub-atomic Particles: Charges

Protons = Positive Charges

Neutrons - Neutral Charges

Nucleus

Electrons – Negative Charges

Atomic Number & Weight

Atomic number = number of protons

(# protons = # electrons)

Atomic weight (mass) = protons + neutrons in an atom.

Therefore, if…..Atomic number = number of protons

Atomic weight = protons + neutrons

Then………

atomic weight - atomic number = # of neutrons

(P + N) (# of P) (# of N)

IsotopesIsotopes = atoms of same element with:

same atomic number (# protons),

different atomic weight (# protons & neutrons)

What is different?

Isotopes1. Unstable…..

• break down

2. Give off radiation

3. Used in medicine

& dating fossils

Electron Configuration determines properties of an atom

• # of electrons = # of protons.• Electron = energy in an atom• Electrons have same weight & charge,

vary in energy content• Farthest from nucleus =

greatest “potential energy”

Atomic Energy Levels

Orbital: where electrons found.

Shells: in orbitals, found in shells

Octet RuleThe first shell: full = 2 electrons.Beyond first shell: full = 8 (or multiples) electrons

Molecule – smallest part of element or compound that has properties of that element or compound.

Compound - Two or more different types of atoms that react or bond together.

Chemical Formulas

1 Symbols for composition of substance.

ex: Hydrogen Cloride = HCl

2 More than 1 atom of same kind = subscript

ex: Water or H2O

Determining Reactivityouter (valence) shell not full = reactive

outer (valence) shell full = not reactive

(inert)

outer shell = valence shell

Atoms want a full outer shell.

To complete outer shell, an atom may:

1. Give up an electron

2. Accept an electron

3. Share an electron

chemical bond = transfer or sharing electrons with another

atom

Electrons possess energy

chemical bond = energy relationship

**Energy Relationship **

1. Energy required to form bond

2. Energy stored in chemical bonds.

3. Energy released when bond is broken.

This concept is a top priority for living organisms.

Types of Reactions

Endergonic reactions – small molecules bonded to form large molecules.

Energy is required.

Exergonic reactions – large molecules broken down into small molecules.

Energy is released.

Chemical reactions indicated by

chemical equations

2H2 + O2 2H2O reactants products

Equal # of atoms exist on both sides

Types of Reactions

• Synthesis A + B C

• Decomposition AB A + B

• Exchange AB + CD AD + CB

• Reversible A + B AB• Oxidation loss of electron (break down)

• Reduction gain of electron (synthesis)

Chemical Bonds

• Ionic

• Covalent

• Polar Covalent

• Hydrogen

Ionic Bonding =

transfer of electrons

Remember…

Atoms are electrically balanced

Electron transfer charge imbalance

creates ions (charged atom)

ionic bond = attraction of - & +

3 P +7 P +9 P +3 P + e-

e-e-

e- e-

e-

e-

e-

e-

e-e-

e-

3 P +7 P +9 P +3 P + e-

e-e-

e- e-

e-

e-

e-

e-

e-e-

e-e-e-

3 P +

3 + and 2 –NET = 1+

10 - and 9+ NET = 1-

Covalent Bonding =

sharing of electrons

1. Atoms linked like a chain.

2. Very strong bonds

(single, double, etc)

3. Found in organic molecules.

(Hydrogen, Oxygen & Carbon)

e-

e-

e-

e-

e-

e-

e-e-

e-

e-e-

e-

e-e-

e-e-

e-

e-

e-

e-

e-e-

e- e-

Polar Covalent Bonds=

Unequal sharing of electrons

• Molecule formed has both:

positive end

negative end

• “polar” molecule

• Water

hydrogen bond =

a slightly “+” hydrogen atom

attracted to

slightly “-”atom in other molecule

• Weak and easily broken

• Many together can be quite strong

• Usually the bond is with O or N

• NOT electron sharing or donating…. It is an ATTRACTION to neighboring molecule

• Illustrated by a broken dotted line.

• http://programs.northlandcollege.edu/biology/Biology1111/animations/hydrogenbonds.html

Chemical properties of water

are essential to life

Living things 70–90% water

Properties of Water• Resists changes in temperature

gains and loses heat slowly

Ocean circulation = Europe’s mild winters even though it is further north than Canada.

Properties of Water• Resists change in state tends to remain liquid high freezing point & high boiling point

Properties of Water

Universal SolventMost substances associate with water.

Facilitates chemical reactions.

solute + solvent = solution

Hydrophilic = “water” “loving”

(attracted to water molecules)

Hydrophobic = “water” “fearing”

(repelled by water molecules)

Properties of Water

• Cohesive and Adhesivemolecules stick together & to other molecules

(effective as a transport medium)

Properties of Water

• High Surface TensionSurface of water hard to break.

Basilisk Lizard

http://www.youtube.com/watch?v=KSLUwmJOo_M

Properties of Water

• Frozen water less dense than liquid water.Ice (solid water)

floats on liquid water.

Water has a slight tendency to

“fall apart” or

DISSOCIATE

OH- called hydroxide ion

H+  called hydrogen ion

(actually H30+)

Water dissociates into equal numbers of:

Others dissociate in water may release

unequal amounts of “+” or “-” ions

Acids = produces H+ ions taste sour

can be corrosive

Bases = can accept H+ ions taste bitter feel slippery

Acidity or Alkalinity

=

measure of relative amount of

H+ and OH- ions

dissolved in a solution

pH scale = indicate acidity and basicity of a solution

Scale ranges from 0 to 14 0-3 is very acidic

7 is neutral

11-14 is very basic or alkaline

Control of pH

is important to organisms!!

• Enzymes function only within a narrow pH range; usually neutral

• Buffers neutralize acids or bases in organisms to help control pH

(by taking up or releasing H+ ions)