1. Chapter 4: Atomic Structure Distinguishing Among Atoms

2. Learning Targets You will determine You will determine the parts of the atom and the function of each subatomic particle. You will identify isotopes, how to write them and how to determine average atomic mass.

3. Funnies Funnies Two molecules are walking down the street; one bumps into the other and says: "Oh, my fault, you okay?” The Second Molecule says: "No, I'm not ok, I've lost an electron!" So the first molecule says: "Are you sure" the second molecule answers, "I'm positive!" You will determine the parts of the atom and the function of each subatomic particle. You will identify isotopes, how to write them and how to determine average atomic mass.

4. The atom Symbols to be familiar with: Protons = p + Neutrons = n 0 Electrons = e - Atoms are always neutral Neutral = Same number of protons and electrons You will determine the parts of the atom and the function of each subatomic particle.

5. The symbol for an atom AXZ A = the mass number (# p + + n 0 ) X = symbol of element Z = the atomic number (number of protons) You will identify isotopes, how to write them and how to determine average atomic mass.

6. Isotopes Isotopes are atoms that have the same number of protons, different number of neutrons Often represented as: element name – mass #. (Example: lithium – 6) You will identify isotopes, how to write them and how to determine average atomic mass.

7. Practice Give the number of protons, neutrons and electrons in the atom symbolized by 201Hg80 Give the symbol to represent the following information: –The cesium atom with a mass number of 132 You will identify isotopes, how to write them and how to determine average atomic mass.

8. Try on your own Give the number of protons, neutrons and electrons in the atom symbolized by 90Sr38 Strontium-90 occurs in fallout from nuclear testing. It can accumulate in bone marrow and may cause leukemia and bone cancer. Give the symbol to represent the following information: –The iron atom with a mass number of 56 You will identify isotopes, how to write them and how to determine average atomic mass.

9. Ions Ions are atoms with a charge –cations (positively charged ion) –anions (negatively charged ion) Ions have a charge because they are gaining or losing electrons from their neutral atom Symbol is element symbol with the ion charge as a superscript (Example: Ca 2+ ) Usually formed when metals combine with nonmetals You will identify isotopes, how to write them and how to determine average atomic mass.

10. Ions that certain groups form on the periodic table You will identify isotopes, how to write them and how to determine average atomic mass.

11. Ions that certain groups form on the periodic table Groups have similar characteristics – one being how many electrons are lost or gained from the neutral atom Ions have unequal numbers of protons and electrons. Different from atoms because numbers are equal. Group 1: 1 + Group 2: 2 + Group 3 or 13: 3 + (there are exceptions) Group 4 or 14: gives or takes electrons Group 5 or 15: 3 - (there are exceptions) Group 6 or 16: 2 - Group 7 or 17: 1 - **know these charges and put on periodic table You will identify isotopes, how to write them and how to determine average atomic mass.

12. Examples For each of the following ions, indicate the total number of protons and electrons in the ion. A. Co 2+ E. S 2- B. Co 3+ F. Sr 2+ C. Cl - G. Al 3+ D. K + H. P 3- You will identify isotopes, how to write them and how to determine average atomic mass.

13. Examples-Answers A. 27 p, 25 eB. 27 p, 24 e C. 17 p, 18 eD. 19 p, 18, e E. 16 p, 18 eF. 38 p, 36 e G. 13 p, 10 eH. 15 p, 18 e You will identify isotopes, how to write them and how to determine average atomic mass.

14. Calculating average atomic mass Isotopes exist in different abundances. For example, an element may have 3 isotopes but one exists over 90%, another less than one % and another less than 10% To continue with that example, each isotope has a respective mass with each percent it represents. You will identify isotopes, how to write them and how to determine average atomic mass.

15. How to calculate average atomic mass 1.Change each percent to decimal. 2.Multiply each decimal and its respective mass for each pair of numbers they give. 3.Add the multiplied values together and round off based on significant digits (match up the mass you calculated to an element on the periodic table to be sure). You will identify isotopes, how to write them and how to determine average atomic mass.

16. Example An element consists of 90.51% of an isotope with a mass of 19.922 amu, 0.27% of an isotope with a mass of 20.994 amu and 9.22% of an isotope with a mass of 21.990 amu. Calculate the average atomic mass and identify the element. You will identify isotopes, how to write them and how to determine average atomic mass.

17. Example cont. 1. Change each percent to decimal form 90.51% .9051 0.27% .0027 9.22% .0922 2. Multiply each decimal number and its respective mass for each pair of numbers given. 90.51% .9051 x 19.922 amu 0.27% .0027 x 20.994 amu 9.22% .0922 x 21.990 amu You will identify isotopes, how to write them and how to determine average atomic mass.

18. Example cont. 3. Add the multiplied numbers together, round off to significant digits (.9051 x 19.922 amu = ) +(.0027 x 20.994 amu = ) +(.0922 x 21.990 amu = ) ELEMENT? You will identify isotopes, how to write them and how to determine average atomic mass.

19. Try on your own The element magnesium has three stable isotopes with the following masses and abundances: IsotopesMass (amu)Abundance Mg-2423.985078.99% Mg-2524.985810.00% Mg-2625.982611.01% Calculate the average atomic mass of Mg. You will identify isotopes, how to write them and how to determine average atomic mass.

20. Answer 24.30501576 rounds to 24.31 Can compare with mass on periodic table to make sure correct. You will identify isotopes, how to write them and how to determine average atomic mass.

21. Homework Page 122-123 42, 45, 47-53, 54-57, 60, 63-64, 67, 70-71 You will determine the parts of the atom and the function of each subatomic particle. You will identify isotopes, how to write them and how to determine average atomic mass.