THE STRUCTURE OF MATTER Physical Science - Chapter 5 Jones.

THE STRUCTURE OF MATTER

Physical Science - Chapter 5

Jones

What will we be learning?

Section 1: Compounds and Molecules Distinguish between compounds and

mixtures (review from Ch 2!). Relate the chemical formula of a compound

to the relative numbers of atoms or ions present in the compound (ALSO review from Ch 2!).

Describe how the chemical structure of a compound affects its properties.

“Compound”

What does this word mean? Something that involves more than one

thing

Examples: Compound fracture Compound sentence Chemical compound

Examples of Chemical Compounds H2O C6H12O6

CO2

Pop Quiz! Are CO and CO2 the same compound? CO

= carbon monoxide, and CO2 = carbon dioxide

Examples of Chemical Compounds H2O C6H12O6

CO2

Pop Quiz! Are CO and CO2 the same compound? CO

= carbon monoxide, and CO2 = carbon dioxide

NO! They have different numbers of oxygen atoms. This makes them different compounds.

How are these atoms put together? Chemical bonds – the attractive forces

that hold different atoms or ions together

Chemical bonds can form between atoms and can also be broken

Na + Cl Na-Cl (written as NaCl, bond formed)

NaCl Na + Cl (bond broken)

Chemical formulas

Chemical formulas represent the numbers and types of atoms in a compound

A compound will always have the same chemical formula

Example: H2O will always be water NaCl will always be sodium chloride

Chemical Structure

The structure will differ between compounds based on the types of bonds between atoms.

1. Strong solids have network structures

1. All molecules in the structure are the same shape, including the angles of the atoms.

2. This arrangement holds the atoms together in a strong rigid structure.

Chemical Structure


2. Some compounds are networks made of bonded ions (ionic compounds)

1. Sodium chloride – Na+1 and Cl-1 ions are attracted to each other and form crystal-shaped structures

2. VERY strong bonds

Chemical Structure


3. Some compounds made of molecules (molecular compounds, also called covalent bonds)

3. Glucose - C6H12O6, not ions, but whole molecules attracted to each other to form crystals

4. Weaker bonds

How does bond strength affect a compound’s properties?

Network Structures

Ionic Compounds

Molecular Compounds/Cov

alent Bonds• VERY STRONG BONDS

•High melting points (in the thousands)

•High boiling points (in the thousands)

•Strong bonds

•High melting points (high hundreds to low thousands)

•High boiling points (high hundreds to low thousands)

•Weaker bonds

•Lower melting and boiling points (usually less than 100)

Therefore, we can conclude that the stronger the bond, the more energy (high melting and boiling points) it takes to break the bonds.

The weaker the bond, the less energy it takes to break the bonds.

Hydrogen Bonds

Another force of attraction in compounds

Forms between adjacent hydrogen atoms of molecules

Strong bonds

Gives water special characteristics Surface tension – the force between water

molecules that gives it a droplet shape

Ch 5 Sec 1 Quiz

Choose the term that best completes each sentence.

1. The atoms in a compound are held together by (chemical bonds/chemical structure).

2. A compound’s (chemical formula/bond angle) shows which atoms or ions it is made up of.

3. Network solids usually have (high/low) melting and boiling points.


Section 2: Ionic and Covalent Bonding Explain why atoms sometimes join to form

bonds. Explain why some atoms transfer their

valence electrons to form ionic bonds, while other atoms share valence electrons to form covalent bonds.

Differentiate between ionic, covalent, and metallic bonds.

Compare the properties of substances with different types of bonds.

Why do atoms bond together? Valence electrons - which atoms have a

full set of 8 electrons and do not need to lose or gain electrons?

Why do atoms bond together? Valence electrons - which atoms have a

full set of 8 electrons and do not need to lose or gain electrons? Noble gases – they are stable

**Atoms form bonds to become stable**

The type of element and how many valence electrons it has determines what it can bond with.

Ionic Bonds

Formed between oppositely charged ions Example: Na+1 + Cl-1 NaCl

Characteristics of ionic bonds & compounds Electrons are transferred (the chlorine atom

GAINED the electron that the sodium atom LOST). Usually between a metal and a nonmetal Stronger than covalent bonds High melting points and boiling points Conduct electricity when dissolved in water Can include polyatomic ions

Ionic Bonds

Polyatomic ions – a charged molecule that contains one or more types of atoms

Always put parentheses around a polyatomic ion and write the charge on the outside

The charge will never change The types of atoms and subscripts will

never change Examples: P 158 Table 3

Formulas of Ionic Compounds In order to write the formula for a

compound, the charges must be determined. Magnesium fluoride

Mg+2 + F-1

Formulas of Ionic Compounds In order to write the formula for a

compound, the charges must be determined. Magnesium fluoride:

Mg+2 + F-1 MgF2

“Switch and drop” the charges to make them subscripts, ignore the + or – signs.

If a Mg atom gives away 2 e-, a fluorine atom can only take 1 e- at a time, so Mg needs to bond to 2 F atoms.

Formulas for Ionic Compounds Try it!

Sodium and Oxygen Potassium and Chlorine Magnesium and oxygen Aluminum and oxygen

Remember: assign charges first, then switch and drop!


Sodium and Oxygen: Na+1 + O-2 Potassium and Chlorine: K+1 + Cl-1 Magnesium and oxygen: Mg+2 + O-2 Aluminum and oxygen: Al+3 + O-2



Sodium and Oxygen: Na+1 + O-2 Na2O Potassium and Chlorine: K+1 + Cl-1 KCl Magnesium and oxygen: Mg+2 + O-2

MgO (reduce!)

Aluminum and oxygen: Al+3 + O-2 Al2O3


Covalent Bonds

Also called molecular bonds Formed between atoms that are sharing electrons

Example: CH4

Characteristics of Covalent bonds & compounds Electrons are shared Usually between two nonmetals Weaker than ionic bonds Lower melting and boiling points Can have double bonds (sharing 2 e-) or triple bonds

(sharing 3 e-) Can be polar or nonpolar

Sometimes covalent compounds share electrons equally, and sometimes they do not.

Polar covalent – a covalent molecule that has an unequal sharing of electrons Example: H2O

Nonpolar covalent – a covalent molecule that has an equal sharing of electrons Example: CH4

Covalent Bonds

All the negativity (electrons) are toward one end of the molecule

The electrons are equally spread out around the atom

Metallic Bonds

Metallic bonds - A bond formed by the attraction between positively charged metal ions and the electrons around them

Characteristics of metallic bonds Neighboring atoms in a sample of a metal

packed together Electrons are free to move from atom to

atom and the atoms can slide past each other easily This explains why metals conduct electricity

and are able flexible

Ch 5 Sec 2 Quiz

Matching: ____ bond formed between positively charged

metal ions and the surrounding electrons ____ bond formed between oppositely

charged ions ____ bond formed between atoms that share

electrons

A) Ionic B) Covalent C) Metallic

Ch 5 Sec 2 Quiz

Matching: _C_ bond formed between positively charged

metal ions and the surrounding electrons _A_ bond formed between oppositely

charged ions _B_ bond formed between atoms that share

electrons

A) Ionic B) Covalent C) Metallic

Bellwork

Get yourselves into exactly SIX groups. Each of you will have your own

worksheet with your own responses. I will assign which column your group

will be doing. After the allowed time period, you will share with us your information!


Section 3: Compound Names and Formulas Name simple ionic and covalent

compounds. Predict the charge of a transition metal

cation in an ionic compound. Write chemical formulas for simple ionic

compounds. Distinguish a covalent compound’s

empirical formula from its molecular formula.

Ionic Compounds

Name Formula Assign the charges to the atoms, “switch

and drop” Magnesium Fluoride Mg+2 + F-1 MgF2

Formula Name Name the metal first, then change the

ending of the nonmetal to –ide Al2O3 Aluminum Oxide

Ionic Compounds w/Polyatomic Ions Name Formula

Assign the charges to the atoms, switch and drop

Use parentheses around the polyatomic ion Aluminum hydroxide Al+3 + (OH)-1 Al(OH)3

Formula Name Name the metal first, and the polyatomic

ion second Do NOT change any endings! Mg(SO4) Magnesium Sulfate

Ionic Compounds w/Transition Metals

The charges of transition metals can change You can determine the charge of the transition

metal by looking at its formula and what it is bonded with

REVERSE “switch and drop”!

Fe2O3 Fe+3 + O-2

FeO Fe+2 + O-2

Predict! What is the charge of the Cu if the formula is CuCl2?


The charges of transition metals can change You can determine the charge of the transition

metal by looking at its formula and what it is bonded with

REVERSE “switch and drop”!

Fe2O3 Fe+3 + O-2

FeO Fe+2 + O-2

Predict! What is the charge of the Cu if the formula is CuCl2?

+2: Cu+2 + Cl-1 CuCl2


The charge of a transition cation can also be told to you using Roman numerals

Copper(II) Sulfate Cu+2 + SO4-2 CuSO4

Iron(III) Oxide Fe+3 + O-2 Fe2O3

Covalent Compounds

Prefix system is used to tell how many of each type of atom there are in the compound

Change the ending to the second element to –ide

N2O4 Dinitrogen tetroxide CO2 Carbon dioxide Boron trifluoride BF3

# of atoms

Prefix

1 Mono-

2 Di-

3 Tri-

4 Tetra-

5 Penta-

6 Hexa-

7 Hepta-

8 Octa-

9 Nona-

10 Deca-

Covalent Compounds

Some compounds have a reduced formula and a non-reduced formula

Empirical formula – simplest or reduced formula

CH2O = Empirical formula Formaldehyde: CH2O Acetic Acid: C2H4O2

Glucose: C6H12O6

Ch 5 Sec 3 Quiz

Which part of an ionic compound should be written first?

How can you tell what the charge is of a transition metal?

What kind of formula gives the numbers of atoms of each element in a compound in the simplest form?

Ch 5 Sec 3 Quiz

Which part of an ionic compound should be written first? Cation, or the metal

How can you tell what the charge is of a transition metal? Look at the molecular formula and what it is

bonded with What kind of formula gives the numbers

of atoms of each element in a compound in the simplest form? Empirical formula

Let’s Review!

P 150 #1-5 (Section 1 Review) P 158 #1-7 (Section 2 Review) P 161 #1-4 (Practice) P 164 #1-6 (Section 3 Review)

THE STRUCTURE OF MATTER Physical Science - Chapter 5 Jones.

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