1. Enrichment! LecturePLUS Timberlake 1

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3. How to read the Periodic Table Pick one of the boxes from the Periodic Table of Elements, and re-draw it here. LecturePLUS Timberlake 3

4. Did I Get It? Circle the number of protons for atoms of each of the following: A. Nitrogen 1) 5 protons 2) 7 protons 3) 14 protons B. Sulfur 1) 32 protons 2) 16 protons 3) 6 protons C. Barium 1) 137 protons 2) 81 protons 3) 56 protons LecturePLUS Timberlake 4 Answers: Nitrogen has 7 protons, Sulfur has 16 protons, Barium has 56 protons

5. Number of Electrons An atom is neutral (has no charge) Number of protons = Number of electrons Atomic number = Number of electrons LecturePLUS Timberlake 5

6. Did I Get It? 1) How many electrons does Nitrogen have? 7 electrons 2) How many electrons does Sulfur have? 16 electrons 3) How many electrons does Barium have? 56 electrons LecturePLUS Timberlake 6

7. Neutrons An atom’s nucleus has protons and neutrons Neutrons have NO charge. Atomic mass = protons + neutrons Atomic mass is sometimes called atomic weight or mass number. LecturePLUS Timberlake 7

8. Atomic Mass on the Periodic Table 11Na22.99 LecturePLUS Timberlake 8 Atomic Number Symbol Atomic Mass

9. Atomic mass is the weighted AVERAGE of all the atomic masses of the isotopes of that atom. Atomic mass is calculated by adding the mass of protons + neutrons. Why do we ignore the mass of electrons when calculating the atomic mass of an element? LecturePLUS Timberlake 9 ISOTOPES of lithium

10. Learning Check An atom of zinc has a mass number of 65. A.Number of protons in the zinc atom 1) 302) 353) 65 B.Number of neutrons in the zinc atom 1) 302) 353) 65 A zinc atom has 30 protons and 35 neutrons. LecturePLUS Timberlake 10

11. An easy way to remember how to read boxes on the periodic table! A tomic number = P rotons and E lectrons M ass number (or atomic Mass) - A tomic number = N eutrons LecturePLUS Timberlake 11

12. Learning Check Write the atomic symbols for atoms with the following: A. 8 p +, 8 n, 8 e - Oxygen B.17p +, 20n, 17e - Chlorine C. 47p +, 60 n, 47 e - Silver LecturePLUS Timberlake 12

13. Learning Check Find the numbers of protons, neutrons, and electrons for the following atoms: A. Magnesium 12 p, 12 e, 12 n B. Phosphorus 15 p, 15 e, 16 n C. Sodium 11 p, 11 e, 12 n LecturePLUS Timberlake 13