chapter 4 the structure of matter i. 4.1 compounds and molecules ii. 4.2 ionic and covalent bonding...

Chapter 4 The Structure of Matter

• I. 4.1 Compounds and Molecules• II. 4.2 Ionic and Covalent Bonding• III. 4.3 Compound Names and

Formulas• IV. 4.4 Organic Chemistry

I. 4.1 Compounds and Molecules• A. What are Compounds?

• 1. Chemical bonds are the attractive force that holds atoms or ions together in compounds.

• 2. Compounds always have the same chemical formula• a. com - with, together, jointly• b. pound - put, position

• c. water H20

• d. table sugar C12H22O11

• e. salt NaCl

• B. A chemical formula shows the types and numbers of atoms or ions making up the simplest unit of the compound.• 1. There is a difference between CO

and CO2

• a. each is made up of C and O but one has 2 O atoms

• 2. The same for H2O and H2O2 (hydrogen peroxide)

• 3. Compounds are always made up of the same elements in the same proportion.

• 4. The formula can tell us what atoms a compound is made of but does not reveal how they are connected.

• 5. The chemical structure show the arrangement of bonded atoms or ions within a substance.• a. Two terms are used to specify the

relative positions of atoms to each other in a compound.− (1) Bond length - gives the distance between

the two nuclei of the atoms− (2) Bond angles tell how these atoms are

oriented when you have three or more atoms in the compound.

• C. Models of compounds can help us to see a compounds structure.• 1. Ball and stick

• a. the ball represents the atom• b. the stick represents the bonds.• c. hard to see the relative size of the

atoms

• 2. Structural formula use the chemical symbol to represent the atoms• a. hard to see the relative size of the

atoms

• 3. Space filled models• a. shows the relative size of the atoms

• b. H2O - hydrogen atoms taking up less space than the oxygen atoms

• c. hard to see the bond angle and lengths

• D. Structure effects properties• 1. Some compounds form crystals

when the chemical bonding is repeated over and over again to form very strong structures.

• a. Quartz SiO2

− (1) bond angle 109.5o

− (2) makes a very strong, rigid structure− (3) rocks made of quartz are very hard and

inflexible− (4) the reason why the melting and boiling

points of quartz is so high – (a) melting point 1700oC– (b) boiling point 2230oC

• 2. Some networks are made of bonded ions• a. NaCl crystal is made of tightly packed

Na+ ions and Cl+ ions• b. this strong attraction produced a high

melting and boiling point− (1) melting point 801oC− (2) boiling point 1413oC

3. Many other compounds due to their structure have very weak attractions between their molecules• a. sugar C12H22O11

• b. melts around 185-186oC

• 4. Comparing strengths of attraction between molecules• a. solids - strongest• b. liquids - medium• c. gases - weakest

Work• 1. p 114• 1-7

write questions and answers

II. 4.2 Ionic and Covalent Bonding

• A. Ionic Bonds• 1. defined - a bond formed between

oppositely charged ions.• 2. There is an electron transfer

• a. one gains electron(s)• b. one loses electron(s)

• 3. mostly between metals and nonmetals

• 4. These form polar molecules which will form a network of ions• a. the positive side attracts the negative

side− (1) how salt crystals are formed

• 5. Formula unit is the smallest ratio of ions in ionic compounds• a. Na+1Cl-1 or Ca+2F2

-1

• b. When melted or dissolved in H2O ionic compounds will conduct electricity because the ions are free to move.

• c. As solids the ions are locked so tightly that they do not conduct electricity.

• B. Metallic Bonds• 1. defined - a bond formed by the

attraction between positively charged ions and the electrons around them.

• 2. Metal to metal • a. example: Cu

• 3. This allows the atoms to• a. conduct electricity

− (1) electrons are free to move from one atom to another atom

− (2) be more flexible to bend and stretch without breaking.– (a) atoms can slide past each other

without breaking their bonds

• C. Covalent Bonds• 1. defined - a bond formed when

atoms share one or more pairs of electrons.

• 2. often formed between nonmetal atoms• a. can be solids, liquids, or gases• b. usually low melting points except for

compounds that form network structures like SiO2

• 3. Do not conduct electricity because the molecules remain intact when melted or dissolved in H2O.

• 4. Electrons are shared not transferred with the nucleus of each atom equally attracting the electrons.

• a. This results in two types of molecules− (1) polar - NH3

− (2) nonpolar - CO2

• b. Atoms may share more than one pair of electrons− (1) O=O− (2) N=N

• c. polar covalent bonds are formed between two different atoms where the shared electrons are attracted to one nucleus more than the other

• D. Poly atomic Ion• 1. defined - an ion made up of two or

more atoms that are covalently bonded and that act like a single ion.

• 2. most names end in -ite and -ate.• a. -ide = the anion named only

− (1) CN-1 - cyanide− (2) OH-1 - hydroxide

• b. -ite = the anion with one less oxygen− (1) SO3

-2 - sulfite

• c. -ate = the anion with one more oxygen− (1) SO4

-2 - sulfate

• 3. Use parentheses around them when more than one is needed in the formula.• a. (NH4)2SO4 - ammonium sulfate

• b. NH4NO3 - ammonium nitrate

• 4. Learn the poly atomic ions with there name, symbol, and charge on page 122 as follows:

acetate C2H3O2-1, carbonate CO3

-2, chlorate ClO3

-1, hydroxide OH-1,

nitrate NO3-1, nitrite NO2

-1,

cyanide CN-1, phosphate PO4-3,

sulfate SO4-2, sulfite SO3

-2,

and ammonium NH4+1

• Page 122• Questions 1-7• Write question and answers• Due at end of class

III. 4.3 Compound Names and Formulas

• A. Compounds have names that distinguish them from other compounds and elements.• 1. BaF2 - barium fluoride vs. BF3 -

boron trifluoride

• B. Ionic Compounds• 1. Include the name of the ions of

which they are composed• a. The cation (positive) is usually the

name of the element− (1) K+ - potassium− (2) Ba+2 - barium

• b. The transition elements we use the element name plus a roman numeral for the oxidation number

in that compound.− (1) Fe+3 - iron III− (2) Fe+2 - iron II− (3) Ti+4 - titanium IV

• c. For the anion (negative) we use the root of the element name and attach an ending− (1) -ide - only the root element makes up the anion− (2) iron II oxide FeO− (3) fluoride - F-1; chloride - Cl-1; bromide – Br -1;

sulfide - S-2

− (4) remember the -ites and -ates have oxygen with the root element

– (a) sulfate - SO4-2; phosphate - PO4

-3

• 2. Writing formulas• a. List the symbols for each ion.

− (1) example: for aluminum fluoride Al F

• b. Write the symbols for the ions and their oxidation number with the cation first.− (1) Al+3 F-1

• c. Find the least common multiple of the ions charges.− (1) for 3 and 1 it is 3− (2) you will need 3 positive charges and 3 negative

charges

• d. Write the chemical formula, indicating with subscripts how many of each ion is needed to make a neutral compound.− (1) +3 -3 = 0

− Al+3 F3-1

• 3. Practice p. 125 1-4

• 4. Some covalent compounds will form more than one compound with the same two elements• a. We use a numeral prefix to indicate

the number of ions in that compound.− Page 126

• b. example: CO - carbon monoxide and CO2 carbon dioxide

• C. Empirical formula• 1. defined - the simplest chemical

formula of a compound that tells the smallest whole number ratio of atoms in the compound.

• D. Molecular formula • 1. defined - a chemical formula that

reports the actual numbers of atoms in molecule of a compound.• a. in some cases the molecular formula is

the same as the empirical formula

− (1) formaldehyde - the empirical formula is CH2O and a molecular formula of CH2O

− (2) acetic acid - the empirical formula is CH2O and a molecular formula of C2H4O2

− (3) glucose - the empirical formula is CH2O and a molecular formula of C6H12O6

• E. Gram molecular mass of a compound

• 1. Ba(OH)2

• Element atoms molar mass/atom molar mass all atoms Ba 1 x 137.33 g/mole = 137.33 g/mole O 2 x 16.0 g/mole = 32.0 g/mole H 2 x 1.0 g/mole = 2.0 g/mole 171.33 g/mole

Ba(OH)2

• Ni3(PO4)4 • Element atoms molar mass/atom molar mass all atoms

Ni 3 x 58.69 g/mole = 176.07 g/moleP 4 x 30.97 g/mole = 123.88 g/moleO 16 x 16.0 g/mole = 256.0 g/mole 555.95 g/mol

Ni3(PO4)4

• 3. class work• a. FeI2• b. MnF3

• c. CrCl2

IV. Organic Chemistry

• A. Polymers• 1. defined - a large organic molecule

made of many smaller bonded units• a. poly - many

• 2. properties are determined by its structure• a. some long thin chains• b. some tangled like a bowl of spaghetti

• 3. most of your plastic and rubber products are polymers• a. elastic - return to original shape

− (1) rubber bands

• b. non elastic - will not return to original shape− (1) plastic soft drink bottles

• Home work• F. page 128

• 1-4; 6-7