April 30 Day 6April 30 Day 6

DRQ: What is an ion?DRQ: What is an ion?

Activities:Activities: DRQ/Review DRQDRQ/Review DRQ Review TestReview Test Chapter 11 IntroductionChapter 11 Introduction

Homework: Complete Why Atoms Homework: Complete Why Atoms Combine Cornell Notes pages 298 -302Combine Cornell Notes pages 298 -302

Chapter 11Chapter 11

Chemical BondsChemical Bonds

Pages 296-321Pages 296-321

Introduction to Chemical Bonds pg 297• Chemical Bonds

• The explosion of fireworks are chemical changes in which chemical bonds are broken

• When a chemical bond is broken, energy is usually released

• The explosion happens when substances in fireworks combine (bond) with oxygen in the atmosphere

• These combinations happen because the electrons in atoms can be given away or borrowed.

• Remember, chemistry is all about electrons, the nucleus of an atom will rarely change – that is called radioactivity.

Fireworks!

• Today's fireworks rely on black powder for two critical functions.• Gas released when the powder combusts first propels the

firework skyward (Newton’s third law of motion)• Later the black powder inside blasts its contents outward

into the patterns that spectators come to see.

• However, other chemical ingredients are also needed; without them fireworks would produce little more than yellowish-orange sparks and white smoke.

• Here is how they make those great colors…

Chapter 11 Chemical Chapter 11 Chemical BondsBondsSection 1: Why Atoms Section 1: Why Atoms CombineCombinePages 298-302Pages 298-302

Words to know:Words to know:– Chemical FormulaChemical Formula– Chemically StableChemically Stable– Chemical BondChemical Bond

Objectives/Study QuestionsObjectives/Study Questions1.1. Describe how a compound differs from the Describe how a compound differs from the

elements that compose it.elements that compose it.

2.2. Explain what a chemical formula represents.Explain what a chemical formula represents.

3.3. State a reason why chemical bonding State a reason why chemical bonding occurs.occurs.

11.1 Summary11.1 Summary1. Compounds have different properties than their

elements. When a bond forms, the properties change.

1. Remember Na (highly reactive metal) and Cl (poisonous green gas) combine to NaCl (edible crystalline solid, dissolves in H2O)

2. H is a light flammable gas, O is also a flammable gas, add two H to an O and you get a clear, colorless liquid.

2. A chemical formula tells you what elements make up the compound and in what ratio.

1. H2O has two atoms of H for every one atom of O2. NaCl has one atom of Na for every one atom of Cl

3. A Chemical bond is how atoms share, lose or gain electrons that will help them become more stable. It joins two atoms together.

1. Na is highly reactive, so is Cl, when they bond with each other, they are less reactive.

Some bonding Some bonding background info…background info… Atoms with a full outer energy level Atoms with a full outer energy level

are are chemically stablechemically stable – they will not – they will not react with another atom to form a react with another atom to form a new substancenew substance

Which elements are these?Which elements are these?

For most atoms, this means it has 8 For most atoms, this means it has 8 outer electrons.outer electrons.– This is called the octet ruleThis is called the octet rule

For H and He what should this rule be For H and He what should this rule be called?called?

More bonding More bonding background…background… Most metals have 3 or fewer outer Most metals have 3 or fewer outer

electrons and tend to lose electrons to electrons and tend to lose electrons to form positive ions.form positive ions.– These will react with negative ions to form These will react with negative ions to form

new compoundsnew compounds

Most non metals have 5 or more outer Most non metals have 5 or more outer electrons and tend to gain electrons to electrons and tend to gain electrons to form negative ions.form negative ions.– These will react with positive ions to form These will react with positive ions to form

new compounds.new compounds.

Cornell NotesCornell Notes pages 298-302 pages 298-302 Take notes on:Take notes on:

– CompoundsCompounds– FormulasFormulas

See examples of these on page 300See examples of these on page 300

– Chemically stable atomsChemically stable atoms Make sure you draw some examples of Make sure you draw some examples of

Dot diagramsDot diagrams

May 1 Day 1May 1 Day 1

DRQ: Why do atoms combine?DRQ: Why do atoms combine?

Activities:Activities: DRQ/Review DRQ (check homework DRQ/Review DRQ (check homework

completion)completion) Review Notes for 11.1Review Notes for 11.1 Section Wrap up page 302Section Wrap up page 302

Homework: Complete Section Wrap upHomework: Complete Section Wrap up

CompoundsCompounds

Most matter is a compound or a mixture of Most matter is a compound or a mixture of compoundscompounds

– A compound has different physical properties than A compound has different physical properties than the elements that combined to form the compound.the elements that combined to form the compound.

The physical properties of the elements are The physical properties of the elements are gone, they are replaced by the physical gone, they are replaced by the physical properties of the new compound.properties of the new compound.

1. Na (highly reactive metal) and Cl (poisonous green gas) combine to NaCl (edible crystalline solid that dissolves in H2O)

2. H is a light flammable gas, O is also a flammable gas, add two H to an O and you get a clear, colorless liquid.

Check out this clip…Check out this clip…

FormulasFormulas

Formulas are made up of chemical symbols.– This is a shorthand way of naming the atoms

in a compound What is the formula for Water? What does the formula mean?

– A subscript is a number “written below” and after the chemical symbol.

– The subscript tells how many atoms of that element are in the compound

Fe2O3 has two Iron atoms chemically combined with three Oxygen atoms

Chemical FormulaChemical Formula

The chemical formula for any The chemical formula for any compound tells compound tells

1.1. What elements it contains What elements it contains 2.2. The ratio of the atoms of those The ratio of the atoms of those

elements.elements.

Look at table 11-1 on page 300.Look at table 11-1 on page 300.– What elements are in each What elements are in each

compound? What is the ratio of compound? What is the ratio of atoms in each compound?atoms in each compound?

Chemically Stable Chemically Stable AtomsAtoms Most elements form compounds Most elements form compounds

because it makes them because it makes them chemically chemically stable.stable.– An atom is chemically stable if its outer An atom is chemically stable if its outer

energy level is filled with electronsenergy level is filled with electrons– A dot diagram is used to quickly show how A dot diagram is used to quickly show how

many outer level electrons an atom has.many outer level electrons an atom has. In this video you’ll see how two Cl In this video you’ll see how two Cl

atoms SHARE two valence electrons.atoms SHARE two valence electrons.– It also shows the use of dot diagrams to It also shows the use of dot diagrams to

indicate the electrons in the outer energy indicate the electrons in the outer energy level and how they are shared in a bond.level and how they are shared in a bond.

– This type of bond is called This type of bond is called covalentcovalent..

Chemical BondsChemical Bonds

A A chemical bondchemical bond is a force that holds the atoms in a is a force that holds the atoms in a substance together.substance together.

You just saw how two Cl atoms can share electrons You just saw how two Cl atoms can share electrons to create a bond.to create a bond.

Here is how a chemical bond forms between Mg and Here is how a chemical bond forms between Mg and OO– When Mg and O become bonded, each Mg loses two When Mg and O become bonded, each Mg loses two

electrons and each O gains two electrons.electrons and each O gains two electrons.– The bond forms because Mg has 2 extra + charges and the The bond forms because Mg has 2 extra + charges and the

O has 2 extra – charges and they are attracted to each O has 2 extra – charges and they are attracted to each other. other.

This video segment should help you visualize this This video segment should help you visualize this process.process.

Valence ElectronsValence Electrons

As you saw in the videos, for most As you saw in the videos, for most elements the outer energy level elements the outer energy level (valence) is most stable when it (valence) is most stable when it contains eight electrons.contains eight electrons.– Why would Krypton be considered Why would Krypton be considered

chemically stable?chemically stable?– Why is H so unstable?Why is H so unstable?

Outer Levels:Outer Levels:Giving, Stealing and Giving, Stealing and SharingSharing Atoms that do not have eight outer level Atoms that do not have eight outer level

electrons will bond with atoms of other electrons will bond with atoms of other elements to fill an octet (eight electrons)elements to fill an octet (eight electrons)

– They do this by gaining, losing or sharing They do this by gaining, losing or sharing electronselectrons

What happens to an atom if it loses an electron?What happens to an atom if it loses an electron? What happens to an atom if it gains an electron?What happens to an atom if it gains an electron? When atoms SHARE electrons they have to be close When atoms SHARE electrons they have to be close

enough that their electron clouds intermingle.enough that their electron clouds intermingle.

Complete the Section Wrap-up Page Complete the Section Wrap-up Page 302302

Questions 1-4 and the Skill BuilderQuestions 1-4 and the Skill Builder ANSWER 1 and 3 IN FULL SENTENCES!ANSWER 1 and 3 IN FULL SENTENCES!

1.1. What happens to the properties of elements What happens to the properties of elements when atoms form compounds? when atoms form compounds? The property of The property of elements…elements…

2.2. Write formulas for Write formulas for a.a. A compound with one calcium atom and two fluorine A compound with one calcium atom and two fluorine

atomsatomsb.b. A compound with two aluminum atoms and three sulfur A compound with two aluminum atoms and three sulfur

atomsatoms

3.3. Why do most elements tend to form compounds? Why do most elements tend to form compounds? Most elements tend to form compounds Most elements tend to form compounds to/becauseto/because

4.4. The label on a box of washing soda states that it The label on a box of washing soda states that it contains Nacontains Na22COCO33. .

a.a. Name the elements in the compound.Name the elements in the compound.b.b. In what ratio are the elements present?In what ratio are the elements present?

Skill BuilderSkill Builder

Look at Table 11-1 on page 300.Look at Table 11-1 on page 300.There are two kinds of chemicals in this There are two kinds of chemicals in this

table, organic and inorganic.table, organic and inorganic.

Chemicals with Carbon in them are Chemicals with Carbon in them are considered organic.considered organic.

Carbon is an amazing element.Carbon is an amazing element.It can form one, two, three and even four It can form one, two, three and even four

bonds.bonds.Check out this video. See if notice anything Check out this video. See if notice anything

about the bonds they show…about the bonds they show…

Re-create this tableRe-create this table

Organize it by the type of Organize it by the type of compound, Organic or Inorganic.compound, Organic or Inorganic.

Hint (there are three organic Hint (there are three organic compounds and six inorganic compounds and six inorganic compounds)compounds)

Not Done?Not Done?

Finish these questions for Finish these questions for homework.homework.

You will find them on page 302 of You will find them on page 302 of your textbook.your textbook.