You have 6 minutes left!!

2Cu + O2 2 CuO• When 127 g of copper

reacts with 32 g of oxygen gas to form copper (II) oxide, not oxygen is left over. How much copper (II) oxide is produced?– A. 32 g– B. 95 g– C. 127 g– D. 159 g

• Elements that are chemically similar to calcium can interfere with the function of neurons. Which of the following is most likely to imitate calcium’s role in the function of neurons?– A. Sodium– B. Potassium– C. Strontium– D. Rubidium

You have 5 minutes left!!

2Cu + O2 2 CuO• When 127 g of copper

reacts with 32 g of oxygen gas to form copper (II) oxide, not oxygen is left over. How much copper (II) oxide is produced?– A. 32 g– B. 95 g– C. 127 g– D. 159 g

• Elements that are chemically similar to calcium can interfere with the function of neurons. Which of the following is most likely to imitate calcium’s role in the function of neurons?– A. Sodium– B. Potassium– C. Strontium– D. Rubidium

You have 4 minutes left!!

2Cu + O2 2 CuO• When 127 g of copper

reacts with 32 g of oxygen gas to form copper (II) oxide, not oxygen is left over. How much copper (II) oxide is produced?– A. 32 g– B. 95 g– C. 127 g– D. 159 g

• Elements that are chemically similar to calcium can interfere with the function of neurons. Which of the following is most likely to imitate calcium’s role in the function of neurons?– A. Sodium– B. Potassium– C. Strontium– D. Rubidium

You have 3 minutes left!!

2Cu + O2 2 CuO• When 127 g of copper

reacts with 32 g of oxygen gas to form copper (II) oxide, not oxygen is left over. How much copper (II) oxide is produced?– A. 32 g– B. 95 g– C. 127 g– D. 159 g

• Elements that are chemically similar to calcium can interfere with the function of neurons. Which of the following is most likely to imitate calcium’s role in the function of neurons?– A. Sodium– B. Potassium– C. Strontium– D. Rubidium

You have 2 minutes left!!

2Cu + O2 2 CuO• When 127 g of copper

reacts with 32 g of oxygen gas to form copper (II) oxide, not oxygen is left over. How much copper (II) oxide is produced?– A. 32 g– B. 95 g– C. 127 g– D. 159 g

• Elements that are chemically similar to calcium can interfere with the function of neurons. Which of the following is most likely to imitate calcium’s role in the function of neurons?– A. Sodium– B. Potassium– C. Strontium– D. Rubidium

You have 1 minute left!!

2Cu + O2 2 CuO• When 127 g of copper

reacts with 32 g of oxygen gas to form copper (II) oxide, not oxygen is left over. How much copper (II) oxide is produced?– A. 32 g– B. 95 g– C. 127 g– D. 159 g

• Elements that are chemically similar to calcium can interfere with the function of neurons. Which of the following is most likely to imitate calcium’s role in the function of neurons?– A. Sodium– B. Potassium– C. Strontium– D. Rubidium

Writing Chemical Formulas

PAGE 27

Chemical Formulas

It is the ratio of atoms bonded together in a compound, for example, X:Y

Where x and y are called the subscripts.

What is a chemical formula?

AxBy

Chemical Formulas

The chemical formula shows that sodium and chlorine atoms combine in a 1:1 ratio:

Every molecule of sodium chloride contains 1 atom of Na and 1 atom of Cl, in a 1:1 ratio.

Remember NaCl?

NaCl=Na1Cl1

Chemical Formulas

In order to be stablestable, a

compound must have net net electrical charge of electrical charge of ZEROZERO.

Net charge

Oxidation Numbers

Tells how many valence electrons are gained, lost or shared when bonding.

A (+) or a (-) is written after the number of electrons, ex: 1+, 1-, 2+, 2-, 3+, 3-ex: 1+, 1-, 2+, 2-, 3+, 3-

For example, a sodium atom always ionizes to Na+ when it combines with other atoms to form a compound. Therefore, we say that Na has an oxidation number of 1+.

Oxidation Numbers

Oxidation Numbers

2+

1+

3+ 3- 2- 1-

Transition Metals

Copy onto your periodic table

Oxidation Numbers

Transition metals (between group IIA and IIIA) have more than one oxidation number.

Roman numerals show the oxidation number.

What about transition metals?

Chemical Formulas

1. Find the oxidation number of the ions.

2. Criss-cross the oxidation numbers to subscripts so that the sum of the oxidation numbers is zero.

So how to write a chemical formula?

Chemical Formulas

1. Find oxidation numbers: iron (III) = Fe3+ (it loses three electrons) oxygen = O2- (it gains two electrons)

2. To determine the ratios of

ions, use the criss-cross method:

Write the formula for compound made of iron (III) and oxygen

Chemical Formulas

Polyatomic ions contain more than one type of ion.

Each polyatomic ion is treated like a single ion!

What about polyatomic ions?

Chemical Formulas

Write a parenthesis around the polyatomic ion and treat it like any other ion...For example, write the formula for aluminum sulfate1. Find the oxidation numbers: Aluminum = Al3+

Sulfate = SO42-

2. Use the criss-cross method: Al3+ SO4

2-

2 3So the formula will be:

Al2(SO4)3

Writing formulas with polyatomic ions