Unit 2 Ecological Biochemistry

Unit 2A: Basic Chemistry

Atoms are incredibly small. Placed side by side, 100 million atoms would make a row only about 1 centimeter long—about the width of your little finger!

Atoms are the Basic Units of Matter

Atoms are made of particles called protons, neutrons, and electrons.

Protons have a positive (+) charge

Electrons have a negative (-) charge

Neutrons are neutral (no charge)

Atoms normally have equal numbers of electrons and protons, making them neutral

What are Atoms made of?

Elements

Elements are pure substances made of only one type of atom

Elements are listed in the periodic table of elements

They are arranged in order of their atomic numbers

An atom is the smallest unit of an element that has the properties of that element

The atomic number of an element is the number of protons (typically the same as the number of electrons)

The mass number of an element is the number of protons plus the number of neutrons

Atomic Number and Mass Number

Element Symbol

Atomic Numbe

r

Mass Numb

er

Number of

Protons

Numbers of

Neutrons

Number of

Electrons

 

Helium

 

He

 

2

 

4

   

2

 

 

Magnesium

 

Mg

 

12

     

12

 

 

Zinc

 

Zn

 

30

 

65

   

35

 

 

Bromine

 

Br

   

80

   

45

 

35 

Aluminum

 

Al

     

13

 

14

 

The five most abundant elements in living things are:

1.Hydrogen – 10%2.Oxygen – 65%3.Nitrogen – 4%4.Carbon – 19%5.Phosphorus – 1%

Important Elements for Biology

HH

A molecule is made when 2 or more of any atom are joined together (Ex: O2, H2O)

A compound is a substance formed by the combination of two or more different elements (Ex: H2O, C6H12O6)

All compounds are molecules, but not all molecules are compounds

Chemical Formula- written shorthand showing the composition of a compound

Molecules, Compounds, and Chemical Formulas

Coefficient: tells how many molecules of that substance (the large number BEFORE the formula)

Subscript: goes with the element symbol preceding the number; tells how many atoms of that element within one molecule of the substance (small number WITHIN the formula).

Chemical Formulas

6

Example 2: 6CO2

What is the coefficient? _______ What is carbon’s subscript? ________ What is oxygen’s subscript? ________ How many molecules of this compound are

represented by this formula? _________ How many atoms TOTAL are present in this molecule?

______

The atoms in compounds are held together by chemical bonds.

Making bonds involves the electrons that surround each nucleus.

The electrons that are available to form bonds are called valence electrons.

Chemical Bonds

The electrons of an atom are spread out in different layers around the nucleus to make an “electron cloud”

These layers are called energy levels

2 electrons go in the first energy level

8 electrons can go in the second energy level and beyond (octet rule)

Valence Electrons

This type of drawing is called a Bohr model

If there are not 8 electrons for the outer level, these empty spots are called vacancies and some electrons are thus unpaired

The unpaired electrons in the outer layer are the valence electrons

The valence electrons can pair with those from other atoms to “fill” the vacancy

This creates a molecule

Valence Electrons (cont.)

Bohr Model vs. Lewis Dot Structure

Bohr Model: shows all of the electrons in their energy levels

Lewis Dot Structure: shows just the valence electrons in the outer energy level

The reactivity of an atom is determined by the number of vacancies in its outer energy level

If there are vacancies, the atom is reactive/unstable

If there are no vacancies, the atom is nonreactive/stable

If the vacancies are filled due to bonding, the molecule is stable

Reactive vs. Stable

1. ionic bonds 2. covalent bonds There are other types of bonds and

interactions but they are not as strong as these two types

The main types of chemical bonds are

1. Ionic Bonds

An ionic bond is formed when one or more electrons are transferred from one atom to another.

An atom that loses electrons becomes positively charged.

An atom that gains electrons has a negative charge.

These positively and negatively charged atoms are known as ions.

These oppositely charged ions have a strong attraction for each other, forming an ionic bond.

2. Covalent Bonds

When electrons are shared by atoms instead of transferred.

The moving electrons travel about the nuclei of both atoms, forming a covalent bond.

A covalent bond can be a…

Single Covalent Bond: atoms share 2 electrons (1 pair)

Double Covalent Bond: atoms share 4 electrons (2 pairs)

Triple Covalent Bond: atoms share 6 electrons (3 pairs)

Bonds between the most important biological atoms will be covalent

The number of bonds each can make is important for the compounds that will be created using these atoms

HONC

H O N C1 2 3 4

 

Hydrogen -can form 1 single bondOxygen- can form 2 single bonds or one double bondNitrogen- can form 3 single bonds or 1 double bond and 1 single bondCarbon- can form 4 single bonds or 2 double bonds, or 1 double bond and 2 single bonds (no quadruple bond!)

This is the number of bonds each of these can form!

Show you the types of elements in the

molecule the number of atoms of each

element AND the arrangement of atoms and

location of covalent bonds. Shows the two dimensional shape of the molecule.

Structural formulas

Chemical Reactions: process that changes or transforms one set of chemicals into another set of chemicals. Involves changes to the chemical bonds that join atoms in compounds.

Reactants: elements or compounds that enter into a chemical reaction

Products: elements or compounds produced by a chemical reaction

HINT: Reactants react to produce products!

Bonds of the reactants are broken and new bonds form in the products

Chemical Reactions

Chemical Equations

Chemical Equation: a mathematical representation of a chemical reaction. It shows the numbers and types of compounds involved. 6O2 + C6H12O6 6CO2 + 6H2O + ___

What process is this equation for?

The Law of Conservation of Matter: matter (atoms and elements) in a chemical reaction cannot be created or destroyed. Only the arrangement of the atoms is changed, NOT the number or types.

Therefore both sides of a chemical equation must be “balanced” (have the same number of atoms).

Balancing Chemical Equations

 C + 2H2 --> CH4

  

Na2SO4 + CaCl2 --> CaSO4 + NaCl

 

C2H6 + O2 --> CO2 + H2O   

2Al2O3 --> 4Al + 3O2

 

 

Are these equations balanced?