CSM Grade 10 Chemistry 2014-2015 HW 3.3 Pg 89 CH3R #7-23 odd, #34 7. a. What are isotopes? Atoms of the same element with different number of neutrons b. How are the isotopes of a particular element alike? They have the same number of protons and usually electrons depending on their charges. Also, their reaction behaviors or other properties are not significantly different than others. c. How are they different? They are different by the number of neutrons meaning their masses are different. Because the number of neutron really determine the stability of an atom, the abudance of each isotopes differ. 8. Copy and complete the following table concerning the three isotopes of silicon, Si. Isotope Number of protons Number of electrons Number of neutrons Si-28 14 14 14 Si-29 14 14 15 Si-30 14 14 16 9. a. What is the atomic number of an element? Atomic Number (Z) = number of protons b. What is the mass number of an isotope? Mass Number = number of protons + number of neutrons c. In the nuclear symbol for deuterium, , identify the atomic number and the mass number. 2 is the mass number and 1 is the atomic number. In general we have 11. Use the periodic table and the information that follows to write the hyphen notation for each isotope described. a. atomic number =2, mass number = 4; He-4 b. atomic number = 8, mass number = 16; O-16 CSM Grade 10 Chemistry 2014-2015 c. atomic number =19, mass number = 39; K-39 13. What is the atomic mass of an atom if its mass is approximately equal to the following? a. that of carbon-12. 4 atomic mass b. 4.5 times as much as carbon-12; 54 atomic mass 15. a. what is the molar mass of an element? Mass present in a mole of pure substance b. to two decimal places, write the molar masses of carbon, neon, iron, and uranium. ; ; ; Practice Problems 17. What is the mass in grams of each of the following? a. 1.00 mol Li; b. 1.00 mol Al; c. 1.00 molar mass Ca; 40.08g Ca d. 1.00 molar mass Fe; 55.84g Fe e. atoms C; that is equal to 1 mol C, so 12.01g C f. atoms Ag; that is equal to 1 mol Ag, so 107.87g Ag 19. Three isotopes of argon occur in nature -- , , and . Calculate the average atomic mass of argon to two decimal places, given the following relative atomic masses and abundances of each of the isotopes: argon-36 (35.97 amu; 0.337%), argon-38 (37.96 amu; 0.063%), and argon-40 (39.96 amu; 99.600%) Isotope amu Abundance Weighted AMU Average amu Ar-36 35.97 0.337% 0.121 Ar-38 37.96 0.063% 0.024 39.94 Ar-40 39.96 99.600% 39.80 CSM Grade 10 Chemistry 2014-2015 21. How many atoms are there in each of the following? a. 1.50 mol Na ( ) ( ) b. 6.755 mol Pb ( ) ( ) c. 7.02 g Si ( ) ( ) ( ) 23. Determine the number of atoms in each of the following: a. 5.40g B ( ) ( ) ( ) b. 0.250 mol S ( ) ( ) c. 0.0384 mol K ( ) ( ) d. 0.02550 g Pt ( ) ( ) ( ) e. g Au ( ) ( ) ( ) .