Conductivity of Solutions CER

​Introduction to Chemical Bonding

By Robert Johnson

Claim

All liquids make electricity more dangerous.

Background information

Valence Electrons
Bohr models
Ions
Octet Rule
oxidation number
Lewis Dot Structures

conductor
insulator
ionic compound
electrolyte
molecular compound
molecular acid

Valence Electrons

The group number = number of valence electrons (1-18, ignore the 1, so Group 17 elements have 7

Exceptions: Transition Metals and Lanthanide and Actinide Series.

Located in the energy level farthest from the nucleus of an atom.

Multiple Choice

Elements in the same column of the periodic table always have the same # of _______ as one another.

• Protons
• Neutrons
• Electrons
• Valence Electrons

Multiple Choice

How many valence electrons does Hydrogen Have?

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Multiple Choice

How many valence electrons does Helium Have?

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Multiple Choice

How many valence electrons does Nitrogen Have?

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Multiple Choice

How many valence electrons does Silicon Have?

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Multiple Choice

How many valence electrons does Lithium Have?

• 1 Valence electron

• 2 Valence electron

• 3 Valence electron

• 4 Valence electron

• 5 Valence electron

Model that helps determine the number of valence electrons for an atom, along with how many energy levels the atom uses.

​

​Bohr Model

Multiple Choice

What is a valence electron?

• Electrons in the first energy shell

• Electrons in the second energy shell

• Electrons in the outer shell

• Total number of electrons

Multiple Choice

How many valence electrons?

• 2

• 3

• 4

• 5

Multiple Choice

How many valence electrons?

• 2

• 3

• 4

• 5

Ions

​Cations (+) and Anion (-)

1. Atoms that gain or lose electrons are called ions.

2. They are involved in chemical bonds.

Multiple Choice

Ions are: 

• atoms with a positive or negative charge
• atoms with no charge
• atoms with ONLY a positive charge
• atoms with ONLY a negative charge

Multiple Choice

What is a positive ion called?

• anion

• cation

• isotope

• covalent

Multiple Choice

What is the charge of an atom that has lost one electron?

• -1
• -2
• +1
• +2

Multiple Choice

Na has 1 valence electron. It will have a charge of _______

• +1

• +2

• -1

• -2

Octet Rule

​Atoms will exchange valence electrons in an attempts to have a full outer energy level.

• 8 valence electrons produce stable atoms.

• The exchange of valence electrons results in bonding, and the creation of compounds.

• Examples Nitrogen (N^3-) =5 valence electrons, Group 15 or 5A

  Needs 3 more valence electrons to get to 8.

  The superscript is negative because electrons are negatively charged.

Multiple Choice

How many electrons would a Nitrogen ion gain/lose? If it has 5 valence electrons.

• lose 5

• gain 5

• lose 3

• gain 3

Multiple Choice

What is the ion formed from Sulfur? If it has 6 valence electrons.

• S⁺²

• S^-2

• S⁺⁶

• S^-6

Multiple Choice

How many electrons would a Calcium ion gain/lose? If it has 2 valence electrons.

• lose 1

• gain 1

• lose 2

• gain 2

Multiple Choice

A Bromine ion gains 1 electron, which of the following is the correct symbol for a Bromine ion?

• Br^-1

• Br⁺¹

• Br⁺⁷

• Br^-7

Multiple Choice

If an element has 3 valence electrons, what charge will likely form on its ion ?

• +3

• +5

• -3

• -5

Oxidation Number

Key Takeaways:

1. Metals tend to form cations, Nonmetals tend to form anions.

2. Metals: oxidation number is the number of valence electrons with a + written after.

3. Nonmetals: oxidation number is 8- number of valence electrons with a - written after.

Na⁺ = Na ¹⁺

Cl^- = Cl ^1-

Ca ²⁺

O ^2-

N ^3-

Al ³⁺

Multiple Choice

What is the oxidation number for elements in Group 2?

• +1

• +2

• -1

• -2

Multiple Choice

What is the oxidation number of elements in Group 18?

• -1

• -2

• 0

• +1

Multiple Choice

What is the oxidation number of elements in the Halogen family (Group 17)?

• +1

• +2

• -1

• -2

Lewis Dot Structure

The element symbol and dots are used to represent valence electrons for an atom.

​This is a useful tool to model chemical bonding

​Don't double up the electrons until you have at least 1 dot in the top, bottom, right , and left. Check out C!

Conductors and Insulators

Metals act as conductors of heat and electricity
Nonmetals act as insulators of heat and electricity

Metals tend to give up valence electrons to form ionic bonds.
Nonmetals tend to give up valence electrons to form ionic bonds.
Nonmetals will "share" electrons with other nonmetals to form covalent or molecular bonds.

Multiple Choice

What is the main difference between conductors and insulators?

• Conductors allow the flow of electricity, while insulators do not.

• Conductors are always solid, while insulators can be liquid or gas.

• Conductors are always transparent, while insulators are always opaque.

• Conductors allow the flow of water, while insulators do not.

Multiple Choice

Give an example of a good conductor of electricity.

• Copper

• Glass

• Wood

• Plastic

Multiple Choice

Explain why metals are good conductors of electricity.

• Metals have no free electrons to conduct electricity.

• Metals are good conductors because they are insulators.

• Metals have a high resistance to the flow of electricity.

• Metals have free electrons that can move easily through the material, allowing electricity to flow.

Multiple Choice

What is the role of electrons in conducting materials?

• They facilitate the flow of electric current.

• They repel electric current

• They have no effect on electric current

• They absorb electric current

Multiple Choice

Why do insulators not conduct electricity?

• Tightly bound electrons

• Low resistance

• Loose electrons

• High conductivity

Multiple Choice

How does the structure of conductors differ from insulators?

• Conductors have a structure that blocks the flow of electrons.

• Insulators have a structure that allows the flow of electrons.

• Conductors have a structure that allows the flow of electrons.

• Conductors and insulators have the same structure.

Multiple Choice

What are some common uses of conductors in everyday life?

• Electrical wiring, metal utensils, metal pipes

• Glassware, ceramic plates, cardboard boxes

• Plastic utensils, rubber pipes, wooden furniture

• Paper clips, rubber bands, plastic bags

Multiple Choice

Explain the concept of resistance in conductors and insulators.

• Resistance is the measure of temperature in conductors and insulators.

• Resistance is the measure of opposition to the flow of electric current in conductors and insulators.

• Resistance is the measure of attraction to the flow of electric current in conductors and insulators.

• Resistance is the measure of speed of electric current in conductors and insulators.

Ionic Compound

Metals transfer valence electrons to nonmetals

Octet Rule comes into play here.
The transfer of valence electrons create a chemical bonds

Multiple Choice

A chemical bond resulting from the electrostatic attraction between positive and negative ions is called a(n)

• covalent bond.
• ionic bond.
• charged bond.
• dipole bond.

Multiple Choice

When metals bond with non-metals they form what type of bonds

• covalent
• ionic
• cooperative
• lewis

Multiple Choice

If I gain electrons I become

• Positive because I've added to my atom
• negative because I've added electrons
• same because i'm balanced
• equal because now I have electrons

Multiple Choice

Metals tend to 

• gain electrons
• lose electrons

Electrolytes

Free moving ions that carry electric charges

• Ionic compounds dissociate when dropped in solution (NaCl) -> Na+ Cl-

• Acids and bases go through ionization with the solvent they are place in.

Multiple Choice

A substance that conducts an electrical current when dissolved in water is called

• catalyst

• metalloid

• electrolyte

• nonelectrolyte

Multiple Choice

Which of the following is not an electrolyte?

• KBr

• LiOH

• RbNO₃

• CH₄

Molecular Compound

​aka Covalent Compound

• Share valence electrons to create strong bonds.

• Can be single, double, or triple bonds

• Single bond = sigma bond ( stronger than ionic)

• Double bond = 1 sigma bond + 1 pi bond (mid)

• Triple bond = 1 sigma + 2 pi bonds (Very strong)
  

Multiple Choice

True or False: a molecular compound is the same thing as a covalent compound.

• False
• True

Multiple Choice

Covalent or molecular compounds involve the sharing of _______ to be considered chemical bonds.

• protons
• electrons

• ions
• valence electrons

Match

Match the following:

• single bond

• double bond

• triple bond

sigma bond

1 sigma bond + 1 pi bond

1 sigma bond + 2 pi bonds

• sigma bond

• 1 sigma bond + 1 pi bond

• 1 sigma bond + 2 pi bonds

Reorder

Reorder the following based on bond strong weakest to highest

• Ionic bond

• single covalent bond

• double bond

• triple bond

1

2

3

4

• 1
• 2
• 3
• 4

Molecular Acid

The strength of an acid determines the amount of ionization that occurs

• Due to the high concentration of mobile ions, solutions of strong acids are strong electrolytes and are excellent conductors of electricity. 

• The low concentration of charge-carrying ions means that weak acid solutions are weak electrolytes and are poor conductors of electricity compared to strong acids.

Multiple Choice

Why are strong acids good conductors?

• Strong acids conduct electricity due to their low molecular weight.
• Strong acids are good conductors because they produce a high concentration of free-moving ions in solution.
• Strong acids are good conductors because they have a high pH level.
• Strong acids are good conductors because they are always in solid form.

Multiple Choice

Why are weak acids poor conductors of electricity?

• Weak acids are strong conductors due to high ion concentration.
• Weak acids completely dissociate into ions in solution.
• Weak acids are good conductors because they contain more electrons.
• Weak acids are poor conductors of electricity because they do not fully dissociate into ions in solution.

Multiple Choice

Compare and Contrast dissociation with ionization.

• Dissociation is the separation of ions in a compound, while ionization is the formation of ions from neutral molecules.
• Dissociation involves the formation of neutral molecules, while ionization separates ions.
• Ionization is the breaking of ionic bonds, whereas dissociation creates covalent bonds.
• Dissociation and ionization are identical processes that both produce neutral compounds.

Experimental Design

Experimental Design Cont.

Evidence

1. Ionic Compounds have measure and often high conductivity

2. Some acids have very high conductivity, some have zero.

3. The true molecular compounds have zero conductivity

Reasoning

• Little to no ions in solution are generated when the conductivity is zero.

• Weak acids generate few ions in solution.

• Molecular compounds have zero conductivity.

• Ionic compounds have high conductivity.

• Small to large amounts of ions are generated in solution when conductivity is high.

• conductive solution allow electricity to pass through making it more dangerous for us than if it were a pure ionic compound.

In theory, a pure molecular solution with 0 conductivity would not conduct electricity .
WARNING: this is beyond dangerous to attempt because a pure ionic solution is difficult to make, and the dangers of electricity are real.