unit 2 ecological biochemistry unit 2a: basic chemistry
TRANSCRIPT
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?