Bell Work:Bell Work:Draw the Lewis dot diagram for the Draw the Lewis dot diagram for the

following elements:following elements:1.1. PotassiumPotassium

2.2. PhosphorousPhosphorous

3.3. CalciumCalcium

4.4. CarbonCarbon

5.5. ChlorineChlorine

Let’s Review Yesterday’s Lesson!Let’s Review Yesterday’s Lesson!

Answer the following questions to the Answer the following questions to the best of your ability.best of your ability.

Use your notes if you get stuck.Use your notes if you get stuck.

Check your answers as we go!Check your answers as we go!

11Section CheckSection Check

Question 1

Electrons are now known to swarm around the nucleus of an atom in a structure known as the _______.

A. electron circleB. electron cloudC. electron configurationD. electron swarm

11Section CheckSection Check

Answer

The answer is B. The “cloud” includes all the regions where an electron might be found.

11Section CheckSection Check

Question 2What information can you learn from this diagram?

11Section CheckSection Check

Answer

This image is an example of an Lewis dot diagram. It tells you that nitrogen contains five electrons in its outer energy level.

11Section CheckSection Check

Question 3

The _______ an energy level is from the nucleus, the _______ electrons it can hold.

A. closer, moreB. closer, lessC. farther, lessD. farther, more

11Section CheckSection Check

Answer

The answer is D. The farthest shells contain the greatest number of electrons.

Chemical Formulas:Chemical Formulas:

Atoms combine (or bond) in predictable Atoms combine (or bond) in predictable numbers.numbers.

We will use our periodic table to figure out We will use our periodic table to figure out what these numbers are.what these numbers are.

Each compound has a specific ratioEach compound has a specific ratio..The ratio compares how many atoms of each The ratio compares how many atoms of each element are in the compound.element are in the compound.

Example: Ammonia’s element ratio is 3 Example: Ammonia’s element ratio is 3 hydrogen atoms to one nitrogen atom.hydrogen atoms to one nitrogen atom.– 3 H : 1 N3 H : 1 N

Example: Water’s element ratio is two Example: Water’s element ratio is two hydrogens to one oxygen.hydrogens to one oxygen.– 2 H : 1 O2 H : 1 O

Example: Salt’s element ratio is one sodium to Example: Salt’s element ratio is one sodium to one chlorine.one chlorine.– 1 Na : 1 Cl1 Na : 1 Cl

Knowing the ratio helps us write the chemical Knowing the ratio helps us write the chemical formula:formula:

A chemical formula uses the chemical symbols to A chemical formula uses the chemical symbols to represent the atoms of the elements and their ratios in a represent the atoms of the elements and their ratios in a chemical compound.chemical compound.

The ratio numbers become a subscript behind its element.The ratio numbers become a subscript behind its element.– A subscript is a number written to the right of a chemical A subscript is a number written to the right of a chemical

symbol and slightly belowsymbol and slightly below..– The subscripts tell you how many atoms of each element The subscripts tell you how many atoms of each element

are present in the compound.are present in the compound.

Example: Carbon dioxide is the gas that we exhale. It’s ratio Example: Carbon dioxide is the gas that we exhale. It’s ratio is 1 carbon atom to 2 oxygen atoms or 1 C : 2 O.is 1 carbon atom to 2 oxygen atoms or 1 C : 2 O.– The chemical formula for Carbon dioxide is COThe chemical formula for Carbon dioxide is CO22..

Examples of writing the chemical Examples of writing the chemical formula:formula:

Compound Compound NameName

Element Element PresentPresent

Atom RatioAtom Ratio Chemical Chemical FormulaFormula

Hydrogen Hydrogen chloridechloride

Hydrogen and Hydrogen and ChlorineChlorine

1 H : 1 Cl1 H : 1 Cl

WaterWater Hydrogen and Hydrogen and OxygenOxygen

2 H : 1 O2 H : 1 O

AmmoniaAmmonia Nitrogen and Nitrogen and HydrogenHydrogen

1 N : 3 H1 N : 3 H

MethaneMethane Carbon and Carbon and HydrogenHydrogen

1 C : 4 H1 C : 4 H

PropanePropane Carbon and Carbon and HydrogenHydrogen

3 C : 8 H3 C : 8 H

How do you find the atom ratio of How do you find the atom ratio of elements in a compound???elements in a compound???

We use the ionization # from the periodic table!We use the ionization # from the periodic table!

4- 3- 2- 1-

0 1+

2+ These are the ionization #’s for each group.

How does this give us the chemical How does this give us the chemical formula?formula?

The ionization # of one element in a The ionization # of one element in a compound crosses over to the other compound crosses over to the other element in the compound.element in the compound.

Example: AmmoniaExample: Ammonia

NN3-3- H H1+1+

NN11 H H33

The ionization # for H is 1+. The ionization # for nitrogen is 3-. When you write the formula, you cross them over. The element ratio is 3 H : 1 N. The chemical formula is NH3.

Find the element ratio and write the Find the element ratio and write the chemical formula for the following:chemical formula for the following:

Water (Hydrogen & Oxygen)Water (Hydrogen & Oxygen)

Salt (Sodium Chloride)Salt (Sodium Chloride)

Calcium chlorideCalcium chloride

Magnesium oxideMagnesium oxide