20 ATOMS: THE BUILDING BLOCKS OF MATTER MODERN CHEMISTRY Copyright by Holt, Rinehart and Winston. All rights reserved.

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1 Name Date Class SECTION 2 continued Section 3.2 (this page only) 9. Below are illustrations of two scientists conceptions of the atom. Label the electrons in both illustrations with a sign and the nucleus in the illustration to the right with a sign. On the lines below the figures, identify which illustration was believed to be correct before Rutherford s goldfoil experiment and which was believed to be correct after Rutherford s gold-foil experiment. a. b. a. b. 10. In the space provided, describe the locations of the subatomic particles in the labeled model of an atom of nitrogen below, and give the charge and relative mass of each particle. a. b. c. a. proton b. neutron c. electron (a possible location of this particle) 20 ATOMS: THE BUILDING BLOCKS OF MATTER MODERN CHEMISTRY Copyright by Holt, Rinehart and Winston. All rights reserved.

2 Isotope Notation Chem Worksheet 4-2 Section 3.3a Name Any given element can have more than one isotope. To distinguish between the different isotopes of an atom, the element is named with its mass number, for example lithium-7. Remember that the mass number is the number of protons and neutrons. When symbols are used to represent an isotope the mass number is written next to the symbol on the top left. The atomic number is written on the bottom left. Recall that the atomic number is the number of protons. EXAMPLES Mass number Atomic number Answer the following questions about atoms. A Z X 1. The identity of an atom is determined by the number of. 2. The particle(s) found inside the nucleus are called:. 3. The number of protons and neutrons combined is called the. 4. In large atoms the number of protons is than the number of neutrons. 5. The number of protons is also called the. 6. Isotopes have the same number of, but different numbers of. 7. The number of protons found in a sulfur atom is. 8. The number of neutrons found in an aluminum-27 atom is. 9. The number of electrons found in a zinc atom is. 10. What is the name of the element with 82 protons?. Give the symbols for the nuclides described by the following particles. Include the atomic number and the mass number protons, 145 neutrons protons, 20 neutrons protons, 10 neutrons protons, 23 neutrons protons, 125 neutrons protons, 22 neutrons protons, 119 neutrons protons, 32 neutrons Determine the number of protons and neutrons from the following symbols. 7 3 Li Lithium-7 3 protons 4 neutrons B N Se Sn Dy Fe Sm Pt Te Cl Ag ? John Erickson, 2004 WS4-2IsotopeNotation

3 Abundance of Isotopes Chem Worksheet 4-3 Section 3.3b Name The atomic mass for each element is reported on the periodic table. This number is a weighted average of the masses of each of the isotopes of an element. For example, the atomic mass of carbon is reported as amu. Carbon is composed primarily of two isotopes: carbon-12 and carbon-13. The atomic mass is calculated from the relative abundance and the masses for these two isotopes. Using the equation below we can calculate the atomic mass for carbon. Atomic Mass = % isotope 1 mass isotope 1 + % isotope 2 mass isotope Atomic mass Carbon-12 makes up 98.93% of all of the carbon atoms, while carbon-13 is about 1.07% abundant. Since the carbon-12 isotope is more abundant, its Isotope % Abundance Mass mass is weighted more in the calculation of Carbon % amu carbon s atomic mass. An example calculation is Carbon % amu done below. Example What is the atomic mass (the weighted average mass) for carbon? - substitute values in equation: atomic mass = (0.9893) (12.000amu) + (0.0107) (13.003amu) (convert % to decimals) - calculate: atomic mass = amu Use the equation for atomic mass to answer the following questions. 1. Argon has three naturally occurring isotopes: argon-36, argon-38, and argon-40. Based on argon s reported atomic mass, which isotope do you think is the most abundant in nature? Explain. 2. Copper is made of two isotopes. Copper-63 is 69.17% abundant and it has a mass of amu. Copper-65 is 30.83% abundant and it has a mass of amu. What is the weighted average mass of these two isotopes? 3. Calculate the atomic mass of silicon. The three silicon isotopes have atomic masses and relative abundances of amu ( %), amu (4.6832%) and amu (3.0872%). 4. Gallium has two naturally occurring isotopes. The mass of gallium-69 is amu and it is % abundant. The mass of gallium-71 is amu and it is % abundant. Find the atomic mass of gallium. 5. Bromine has two naturally occurring isotopes. Bromine-79 has a mass of amu and is 50.69% abundant. Using the atomic mass reported on the periodic table, determine the mass of bromine-81, the other isotope of bromine. 6. Calculate the atomic mass of lead. The four lead isotopes have atomic masses and relative abundances of amu (1.4%), amu (24.1%), amu (22.1%) and amu (52.4%). 7. Antimony has two naturally occurring isotopes. The mass of antimony-121 is amu and the mass of antimony-123 is amu. Using the average mass from the periodic table, find the abundance of each isotope. (Remember that the sum of the two abundances must be 100). John Erickson, 2005 WS4-3AbundanceOfIsotopes

4 WS 3.1 Protons, Neutrons, Electrons 1. Fill in the table below with the correct numbers (first one is done as an example) atomic mass # of particles # of # of # of symbol name number number charge in nucleus protons neutrons electrons 23 11Na sodium Cu gold K K K C 1+ Section 3.3c How many n's are there in an atom of P-33? How many p's in an Fe ion? 3. How many total particles (p, n & e's) are in an O-16 atom? In a F ion? 4. All chromium particles must have the same number of (p, n or e?) 5. (p, n, or e?) The # of determines what element a particle is, the # of determines what isotope of that element, and the # of determines the particle's overall charge. 6. An atom has a mass # of 62 and has 33 neutrons; what element is this atom? 7. A particle has 13 p, 14 n, and 10 e; what is its mass #? What is the particle's charge? What element is it? 8. A particle has 35 p, 45 n, and 36 e; what is its mass #? What is the particle's charge? What element is it? 9. If a mercury-198 atom were to lose a proton, it would become a. 10. If two lithium-6 atoms fused (joined together), it would create a. 11. If a thorium-234 atom absorbed a neutron, it would become a. 12. If a uranium-238 atom were split into two equal halves, it would make two. Ans (IRO+2; no names for #1): p p n e 1 H C 14 N 3-25 Mg Al 35 Cl 1- Cu 78 Kr 119 Pd Br 197 Au 198 Au 235 Th 238 U

5 Section 3.3d (2 pages, may use "bar = bar" WS 5.2 The Mole SHOW ALL WORK using DIMENSIONAL ANALYSIS Circle the leftover answer & units in answer bank when done 1. Please convert these measurements into moles: a) 9.03 x C atoms b) 6.02 x Li atoms c) 9.03 x CO 2 molecules d) 2.44 x H 2 O molecules 2. Please convert these measurements into atoms / molecules: ('cules = unofficial abbrev. for molecules) a) 3.50 moles K b) moles NF 3 c) 62.5 moles CO 2 d) 7.90 x 10 4 moles H 2 O 3. Please convert these measurements into moles: a) 56.7 g C b) 5.67 g NF 3 c) 44.0 g CO 2 d) 8.43 x 10 5 g Ag 4. Please convert these measurements into mass (grams): a) 3.50 moles K b) moles NF 3 c) 62.5 moles CO 2 d) 7.9 x 10 9 moles H 2 0 Circle leftover answer and unit Ans: (IRO+1) E E E E E28 Units: (IRO+1) mol mol mol mol mol mol mol mol mol g g g g atom 'cules 'cules 'cules

6 WS 5.2 continued Please convert these measurements into atoms / molecules: a) 17.4 g K b) g NF 3 c) 34.3 kg CO 2 d) 3.90 x 10 4 g H 2 O 6. Please convert these measurements into mass (grams): a) x C atoms b) 7.54 x Na atoms c) 6.98 x CO 2 molecules d) 1 H 2 O molecule 7. How many molecules are present in 15.4 g of CO2? 8. a) What would be the mass of a 16.9 mole sample of propane (C 3 H 8 )? b) How many propane molecules would it contain? c) How many C atoms would it contain? (hint- multiply ans. in 'b' by # of C atoms in formula) a: b: c: 9. How many Au atoms are there in a 2.3 cm x 5.6 cm x 12.7 cm block of gold? (D = 19.3 g/ml) (hint- use density formula to find mass. Then convert mass into atoms) 10. a) How much would 3.45 x C 12 H 22 O 11 molecules weigh? b) How many total atoms (C, H & O combined) would it contain? (hint- multiply 3.45 E 21 by total # of atoms in formula) a: b: moles of O 2 gas has a volume of 44.8 L at standard conditions. What would be oxygen's density under those conditions? (D=m/V) (hint- change moles to grams. Then use density equation) Ans 5-11 (IRO+1): 3E E E E E E23 9.6E E E E E27 Units 5-11 (IRO+1): g g g g g g g g/l atom atom atom atom atom 'cules 'cules 'cules 'cules 'cules

7 Name Date Class MR3 (2 pages) CHAPTER 3 REVIEW Atoms: The Building Blocks of Matter MIXED REVIEW SHORT ANSWER Answer the following questions in the space provided. 1. The element boron, B, has an atomic mass of amu according to the periodic table. However, no single atom of boron has a mass of exactly amu. How can you explain this difference? 2. How did the outcome of Rutherford s gold-foil experiment indicate the existence of a nucleus? 3. Ibuprofen, C 13 H 18 O 2, that is manufactured in Michigan contains 75.69% by mass carbon, 8.80% hydrogen, and 15.51% oxygen. If you buy some ibuprofen for a headache while you are on vacation in Germany, how do you know that it has the same percentage composition as the ibuprofen you buy at home? 4. Complete the following chart, using the atomic mass values from the periodic table: Compound Mass of Fe (g) Mass of O (g) Ratio of O:Fe FeO Fe 2 O 3 Fe 3 O 4 MODERN CHEMISTRY ATOMS: THE BUILDING BLOCKS OF MATTER 23 Copyright by Holt, Rinehart and Winston. All rights reserved.

8 Name Date Class MIXED REVIEW continued 5. Complete the following table: Atomic Mass Number Number Number Element Symbol number number of protons of neutrons of electrons Sodium 22 F PROBLEMS provided. Write the answer on the line to the left. Show all your work in the space 6. a. How many atoms are there in 2.50 mol of hydrogen? b. How many atoms are there in 2.50 mol of uranium? c. How many moles are present in 107 g of sodium? 7. A certain element exists as three natural isotopes, as shown in the table below. Percent natural Isotope Mass (amu) abundance Mass number Calculate the average atomic mass of this element. 24 ATOMS: THE BUILDING BLOCKS OF MATTER MODERN CHEMISTRY Copyright by Holt, Rinehart and Winston. All rights reserved.