1. Activity #4: Chemical Bonds

2. Vocabulary Covalent bond Chemical bond Reactants Stable/unreactive
Products
Unstable/reactive
Valence level
Charge
Octet rule
Chemical equation
HONC
Law of conservation of matter
Reactivity

3. Chemical Bonds Atoms in compounds are held together by chemical bonds
Making bonds involves the electrons that surround each nucleus
Electrons that are available to form bonds are called valence electrons

4. Valence Electrons
Electrons of an atom are spread out in different layers around the nucleus to make an “electron cloud”
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)

5. Valence Electrons
If there are not 8 electrons for the outer level, these empty spots are called vacancies and some electrons are unpaired
Unpaired electrons in the outer layer are the valence electrons
Valence electrons can pair with those from other atoms to “fill” the vacancy
Creates a molecule

6. Bohr Model vs. Lewis Dot Structure
Lewis Dot Structure: shows just the valence electrons in the outer energy level
Bohr Model: shows all of the electrons in their energy levels

7. Practice
Element
Bohr
Lewis Dot
Carbon
Nitrogen

8. Reactive vs. Stable
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

9. Types of Chemical Bonds
1. ionic bonds
2. covalent bonds
There are other types of bonds and interactions but they are not as strong

10. Ionic Bonds
Formed when one or more electrons are transferred from one atom to another
Atom that loses electrons becomes positively charged
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

11. Covalent Bonds Electrons are shared by atoms instead of transferred
Moving electrons travel about the nuclei of both atoms, forming a covalent bond.

12. 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)

13. HONC
This is the number of bonds each of these can form!
H O N C
Bonds between the most important biological atoms will be covalent
Number of bonds each can make is important for the compounds that will be created using these atoms
Hydrogen -can form 1 bond
Oxygen- can form 2 bonds
Nitrogen- can form 3 bonds
Carbon- can form 4 bonds

14. Ionic vs. Covalent Video Quiz

15. Chemical Reactions
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

16. Chemical Equations
What process is this equation for?
Cellular Respiration
Chemical Equation: a mathematical representation of a chemical reaction
Shows the numbers and types of compounds involved
6O C6H12O  CO H2O ___
ATP
Reactants
Products

17. Balancing Chemical Equations
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
Both sides of a chemical equation must be “balanced” (have the same number of atoms)

18. Practice Are these equations balanced? C + 2H2 --> CH4
C + 2H2 --> CH4
Na2SO4 + CaCl2 --> CaSO4 + NaCl
C2H6 + O2 --> CO2 + H2O
2Al2O3 --> 4Al + 3O2
Yes No No
Yes