South Pasadena • Chemistry



AP Chemistry Name ________________________________

Period ___ Date ___/___/___

2 – Atoms to Molecules

Notes: Atomic Structure

Parts of Atoms:

Most people already know that the atom is made up of three main parts, the _______________ and ______________ in the nucleus and the ______________ somewhere outside of the nucleus.

Let’s summarize:

| |proton |neutron |electron |

|symbol | | | |

|charge | | | |

|location | | | |

|mass | | | |

|size (see below) | | | |

Let’s make this more visual using information from the Chart of Fundamental Particles.

If the proton were 10 cm in diameter… the size of an orange, how big would everything be?

|object |actual size |model size |model |

|proton |10-15 m |10 cm |orange |

|neutron |10-15 m | | |

|electron |10-18 m | | |

|atom |10-10 m | | |

The atom is often represented as a miniature ___________ _____________. Draw it:

The mass of the atom is due to the _____________________________

The size of the atom is due to the __________________

How Many Particles in Each Atom?

The particle that defines the identity of an atom is the _____________. (shown on the periodic table)

Every hydrogen atom has ___ proton.

Every magnesium atom has ___ protons.

Any atom that has 23 protons is _________________.

Any atom that has 92 protons is _________________.

The mass of an atom is mostly from the ___________ and ____________.

Find O on the periodic table. Its mass is ______ amu.

It has ___ protons. It must have ___ neutrons.

Electrically neutral atoms (as opposed to ions) have one electron for every proton.

Fill in this chart for these neutral atoms:

|Atom |Mass |protons |neutrons |electrons |

|He | | | | |

|Si | | | | |

|Be | | | | |

|H | | | | |

|Rn | | | | |

|Ar | | | | |

|F | | | | |

|Pb | | | | |

If the mass is not close to a whole number, it is because the atom has several _____________. These are atoms with the same number of ___________ but different numbers of _____________.

Chlorine has two isotopes: Cl-35 ( ___ p+ & ___ n() and Cl-37 ( ___ p+ & ___ n().

WS#1: Isotopes

1. Give the mass number of each of the following atoms:

(a) an iron atom with 30 neutrons

(b) an americium atom with 148 neutrons

(c) a tungsten atom with 110 neutrons

2. Give the complete symbol ([pic]) for each of the following atoms:

(a) nitrogen with 8 neutrons

(b) zinc with 34 neutrons

(c) xenon with 75 neutrons

3. How many electrons, protons, and neutrons are there in an atom of:

(a) carbon-13,[pic]

(b) copper-63,[pic]

(c) bismuth-205,[pic]

4. Fill in the blanks in the table (one column per element).

|Symbol |[pic] |[pic] | | |

|Number of protons | | |78 | |

|Number of neutrons | | |117 |46 |

|Number of electrons | | | |36 |

|in the neutral atom | | | | |

|Name of element | | | | |

5. Radioactive americium-241 is used in household smoke detectors and in bone mineral analysis. Give the number of electrons, protons, and neutrons in an atom of americium-241.

6. Which of the following are isotopes of element X, with atomic number of 9: [pic],[pic],[pic], and [pic].

7. Verify that the atomic mass of magnesium is 24.31 amu, given the following information:

[pic], mass = 23.985042 amu; percent abundance = 78.99%

[pic], mass = 24.985837 amu; percent abundance = 10.00%

[pic], mass = 25.982593 amu; percent abundance = 11.01%

8. Copper has two stable isotopes,[pic]and [pic], with masses of 62.939598 amu and 64.927793 amu, respectively. Calculate the percent abundances of these isotopes of copper.

9. Strontium has four stable isotopes, Strontium-84 has a very low natural abundance, but [pic],[pic], and [pic]are all reasonably abundant. Which of these more abundant isotopes predominates?

WS#2: The Nuclear Atom (ChemActivity #1)

[pic]

ALL of the answers to this worksheet can be logically figured out by looking at the Schematic Diagrams for Various Atoms , the Periodic Table, and discussing with your partners. All of the information you need is here somewhere. Determine each answer and be able to give convincing reasons for each answer. Good luck.

1. How many protons are found in 12C? 13C? 13C−?

2. How many neutrons are found in 12C? 13C? 13C−?

3. How many electrons are found in 12C? 13C? 13C−?

4. Based on the model,

a) what do all carbon atoms (and ions) have in common?

b) what do all hydrogen atoms (and ions) have in common?

5. What is the significance of the atomic number, Z, above each atomic symbol in the periodic chart?

6. What do all nickel (Ni) atoms have in common?

7. How is the mass number, A, (left-hand superscript next to the atomic symbol) determined?

8. What structural feature is different in isotopes of a particular element?

9. a) What feature distinguishes a neutral atom from an ion?

b) How is the charge on an ion determined?

10. Where is most of the mass of an atom, within the nucleus or outside of the nucleus?

Explain your reasoning.

11. Complete the following table:

|Isotope |Atomic |Mass |Number of |

| |Number |Number |electrons |

| |Z |A | |

|31P |15 | | |

|18O | | |8 |

| |19 |39 |18 |

|58Ni2+ | |58 | |

WS#3: Notes About Scientists

Using the Internet, fill in information about each scientist. Some are our “signpost” scientists who made major contributions toward our understanding of the atom. Others contributed smaller important ideas that help with the overall story.

|Scientist |Their “Experiment” |What they added to the atomic theory |Name of their model |

|Democritus | | | |

|John Dalton | | | |

|J.J. Thomson | | | |

|Ernest Rutherford | | | |

|Scientist |Notes: (What did they do that helped develop the atomic theory?) Refer to Question 8 in the Ch 2 Study Questions. |

|Michael Faraday | |

|Joseph Proust | |

|Antoine Lavoisier | |

|Robert Millikan | |

|Benjamin Franklin | |

|Henri Becquerel | |

|Marie Curie | |

|James Chadwick | |

|Henry Moseley | |

|Dmitri Mendeleev | |

WS#4: Study Questions

“The one quality which sets one man apart from another — the key which lifts one to every aspiration while others are caught up in the mire of mediocrity — is not talent, formal education, nor brightness — it is self-discipline. With self-discipline, all things are possible. Without it, even the simplest goal can seem like the impossible dream.” Theodore Roosevelt (1858-1919)

1. Explain, at an atomic or molecular level, what happens when

a. water freezes to form ice

b. copper and tin combine to form bronze

c. rainwater evaporates from the pavement

2. Which of the following atoms are isotopes of the same element? Identify the elements of these isotopes and describe the number of protons and neutrons in the nucleus of them all.

[pic]X [pic]X [pic]X [pic]X [pic]X [pic]X [pic]X [pic]X [pic]X

3. There are three naturally occurring isotopes of neon:

neon-20 mass 19.9924 amu abundance 90.84%

neon-21 mass 20.9940 amu abundance 0.260%

neon-22 mass 21.9914 amu abundance 8.90%

a. Without calculation, what is the approximate atomic mass of neon?

b. Calculate the actual atomic mass.

4. Uranium has an atomic mass equal to 238.0289. It consists of two isotopes: uranium-235 with an isotopic mass of 235.044 amu and uranium-238 with an isotopic mass of 238.051. Calculate the % abundance of the uranium-235 isotope.

5. From amongst the elements sodium, chlorine, nickel, argon, calcium, uranium, and oxygen, select the alkali metal, the alkaline earth metal, the transition metal, the actinide, the halogen, the noble gas, and the chalcogen (Group 6A).

6. To illustrate Robert Millikan’s determination of the charge on an electron, suppose that you were given the task of determining the mass of a single jelly bean given the following experimental data:

Various scoops of jelly beans were weighed and the following masses determined. The number of jelly beans in each scoop was not known.

Masses (in grams) of ten different scoops:

|4.96 |8.68 |13.64 |7.44 |

| | | | |

|CO2 |N2O |NaOCl |Al2S3 |

| | | | |

II. Fraction and Percent Composition

It is useful to determine how much of a compound’s mass is made up of each element. Water, H2O, for example has a molar mass of 18.02 g. The H’s mass is 2(1.0079) = 2.02 g. The O’s mass is 16.00 g.

We can set up fractions for each element: H = [pic]= 0.112 = 11.2%. O = [pic]= 0.888 = 88.8%.

This is called the percent composition. The fraction composition is a good in-between step.

Determine the fraction and percent composition of each element below (answer to one decimal place):

|1. H2SO4 | | | |

|2. Ca(OH)2 | | | |

|3. HC2H3O2 | | | |

|4. CO2 | | |

|5. N2O | | |

|6. NaOCl | | | |

|7. Al2S3 | | | |

WS#6: Mole Calculations

Level 1

1 mole = 6.02 x 1023 molecules = 22.4 L (@ STP)

1. Calculate the mass of 1.58 moles CH4. [molar mass CH4 = 16.0 g/mol]

G: 1.58 moles CH4

D: ? g CH4

[pic]

2. What volume will 7.29 moles of CO2 gas occupy at STP?

G: 7.29 moles CO2

D: ? L CO2

[pic]

3. How many molecules are there in a 0.00583 mole sample of H2O?

G: 0.00583 moles H2O

D: ? molecules H2O

[pic]

4. What mass of CO2 gas occupies a volume of 100. Liters at STP? [molar mass CO2 = 44.0 g/mol]

G: 100. Liters CO2

D: ? g CO2

[pic]

5. How many molecules are in a 35.0 gram sample of H2O? [molar mass H2O = 18.0 g/mol]

G: 35.0 g H2O

D: ? molecules H2O

[pic]

6. What volume will 5.25 x 1022 molecules of CH4 occupy at STP?

G: 5.25 x 1022 molecules CH4

D: ? L

[pic]

Level 2

1 mole = 6.02 x 1023 molecules = 22.4 L (@ STP)

1. Calculate the mass of 2.19 moles CH4. [molar mass CH4 = 16.0 g/mol]

G:

D:

[pic]

2. What volume will 2.22 moles of CO2 gas occupy at STP?

G:

D:

[pic]

3. How many molecules are there in a 0.127 mole sample of H2O?

G:

D:

[pic]

4. What mass of CO2 gas occupies a volume of 395 Liters at STP? [molar mass CO2 = 44.0 g/mol]

G:

D:

[pic]

5. How many molecules are in a 0.250 gram sample of H2O? [molar mass H2O = 18.0 g/mol]

G:

D:

[pic]

6. What volume will 3.01 x 1022 molecules of CH4 occupy at STP?

G:

D:

[pic]

Level 3

1 mole = 6.02 x 1023 molecules = 22.4 L (@ STP)

1. Calculate the mass of 7.23 moles CH4. [molar mass CH4 = 16.0 g/mol]

G:

D:

2. What volume will 9.35 moles of CO2 gas occupy at STP?

G:

D:

3. How many molecules are there in a 0.0752 mole sample of H2O?

G:

D:

4. What mass of CO2 gas occupies a volume of 10.8 Liters at STP? [molar mass CO2 = 44.0 g/mol]

G:

D:

5. How many molecules are in a 1.44 gram sample of H2O? [molar mass H2O = 18.0 g/mol]

G:

D:

6. What volume will 1.21 x 1024 molecules of CH4 occupy at STP?

G:

D:

WS#7: Writing Formulas and Naming Compounds

Introduction

Writing formulas and naming compounds can be confusing because there are different types of compounds that follow different rules. Additionally, some compounds (H2O, NH3, CH4, etc.) simply have common names that must be memorized.

The two types of compounds we will focus on first are ionic compounds (formed from positive and negative ions) and binary nonmetal compounds (molecular compounds). Later we will add acids. So… you must recognize the type of compound before you try to name it. [Note: + ion = “cation” and – ion = “anion”.]

| |Ionic |Binary Nonmetal |

|Formula |+ ion before – ion |usually the less electronegative atom is first |

| |ex: NaCl (NH4)2SO4 Al2S3 |ex: CO CO2 N2O |

|Naming |Name of cation + name of anion |Indicate the number (mono, di, tri, and kind of atoms. First element is |

| | |simply name of element. Second element name ends with “ide” |

| |sodium chloride | |

| |ammonium sulfate |carbon monoxide |

| |aluminum sulfide |carbon dioxide |

| | |dinitrogen monoxide |

I. Writing Ionic Formulas

| |Cl− |NO3− |S2− |

|Cu2+ |OH− | | |

|Ba2+ |SO42− | | |

|NH4+ |Cr2O72− | | |

|Ag+ |C2H3O2− | | |

|Fe3+ |S2− | | |

|mono |di |tri |tetra |

|nitrogen trifluoride | |phosphorus trichloride | |

|nitrogen monoxide | |phosphorus pentachloride | |

|nitrogen dioxide | |sulfur hexafluoride | |

|dinitrogen tetroxide | |disulfur decafluoride | |

|dinitrogen monoxide | |xenon tetrafluoride | |

IV. Naming Binary Nonmetal Compounds

|Name |Formula |Name |Formula |

| |CCl4 | |HBr |

| |P4O10 | |N2F4 |

| |ClF3 | |XeF3 |

| |BCl3 | |PI3 |

| |SF4 | |SCl2 |

V. Practice for Both Types of Compounds

|Formula |Name | |Formula |Name |

|HCl | | | |carbon dioxide |

|PCl5 | | | |ammonium carbonate |

|K2S | | | |sulfur dichloride |

|NiSO4 | | | |calcium iodide |

|ClF3 | | | |boron trifluoride |

|OF2 | | | |phosphorus triiodide |

|Al(OH)3 | | | |magnesium perchlorate |

|NCl3 | | | |potassium permanganate |

|(NH4)3PO4 | | | |aluminum phosphate |

|S2Cl2 | | | |dioxygen difluoride |

WS#8: Hydrate and Composition Problems

1. Cupric chloride, CuCl2, when heated to 100(C is dehydrated. If 0.235 g of CuCl2 · x H2O gives 0.185 g of CuCl2 on heating, what is the value of x?

2. The “alum” used in cooking is potassium aluminum sulfate hydrate, KAl(SO4)2 · x H2O . To find the value of x, you can heat a sample of the compound to drive off all of the water and leave only KAl(SO4)2. Assume you heat 4.74 g of the hydrated compound and that the sample loses 2.16 g of water. What is the value of x?

3. If “Epsom salt,” MgSO4 · x H2O is heated to 250(C, all the water of hydration is lost. On heating a 1.687-g sample of the hydrate, 0.824 g of MgSO4 remains. What is the formula of Epsom salt?

4. When CaSO4 · x H2O is heated, all of the water is driven off. If 34.0 g of CaSO4 (molar mass = 136) is formed from 43.0 g of CaSO4 · x H2O, what is the value of x?

WS#9: Study Questions

1. a. The structural formula for acetic acid is CH3CO2H. What is its empirical formula; what is its molecular

formula?

b. The molecular formula of acrylonitrile is C3H3N. Look up in the text, and draw, its structural formula.

c. The molecular formula of aspartame (nutrasweet) is C14H18O5N2. Look up in the text, and draw, its

structural formula.

2. The formulas for ethanol and ammonium nitrate are C2H5OH and NH4NO3. In what respects are these formulas and compounds different?

3. The molecular formula for both butanol and diethylether is C4H10O. Write structural formulas for both and show how they are different. Are any other structures possible?

4. Name the polyatomic ions:

CH3CO2-

H2PO4-

SO32-

HCO3-

Cr2O72-

ClO4-

5. What are the formulas of the polyatomic ions:

phosphate nitrite

sulfate cyanide

bisulfite chlorite

6. Write the ions present in the following salts and predict their formulas:

potassium bromide

calcium carbonate

magnesium iodide

lithium oxide

aluminum sulfate

ammonium chlorate

beryllium phosphate

7. Name the following ionic salts:

| (NH4)2SO4 | Co2(SO4)3 |

|KHCO3 |NiSO4 |

|Ca(NO3)2 |AlPO4 |

8. Name the following binary compounds of the nonmetals:

CS2

SF6

IF5

N2H4

PCl5

Cl2O7

SiCl4

GeH4

P4O10

S4N4

OF2

IF7

9. What are the formulas for the following binary compounds?

| silicon dioxide | phosphine |

|boron trifluoride |silicon carbide |

|xenon tetroxide |phosphorus tribromide |

|dinitrogen pentoxide |disulfur dichloride |

|bromine trifluroide |hydrogen selenide |

|carbon tetrachloride | |

10. a. How many moles are present in 128 grams of sulfur dioxide?

b. What is the mass of 3 moles of oxygen molecules?

c. If 5 moles of a metallic element have a mass of 200 grams, which element is it?

d. What is the molar mass of methane CH4?

e. What is the mass of 9 moles of fluorine molecules?

f. 102 grams of a gas contains 6 moles. What is its molar mass?

g. How many grams are there in one mole of benzene C6H6?

h. How many moles of nitrogen atoms are there in 6 moles of TNT (trinitrotoluene CH3C6H2(NO2)3)?

i. What is the molar mass of TNT?

11. What is the percent by mass of nitrogen in ammonium nitrate?

12. The hydrocarbons ethylene (molar mass 28 g/mol), cyclobutane (molar mass 56 g/mol), pentene (molar mass 70 g/mol), and cyclohexane (molar mass 84 g/mol), all have the same empirical formula. What is it? Write the molecular formulas for these four compounds.

13. A compound was analyzed and found to contain 76.57% carbon, 6.43% hydrogen, and 17.00% oxygen by mass. Calculate the empirical formula of the compound. If the molar mass of the compound is 94.11g/mol, what is the molecular formula of the compound?

14. A compound was analyzed and found to contain 53.30% carbon, 11.19% hydrogen, and 35.51% oxygen by mass. Calculate the empirical formula of the compound. If the molar mass of the compound is 90.12 g/mol, what is the molecular formula of the compound?

15. A 15.67 g sample of a hydrate of magnesium carbonate was carefully heated, without decomposing the carbonate, to drive off the water. The mass was reduced to 7.58 g. What is the formula of the hydrate?

16. Anhydrous lithium perchlorate (4.78 g) was dissolved in water and re-crystallized. Care was taken to isolate all the lithium perchlorate as its hydrate. The mass of the hydrated salt obtained was 7.21 g. What hydrate is it?

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