This document discusses key concepts in atomic structure including: 1) Atoms are made of subatomic particles including protons, neutrons, and electrons. The atomic number is the number of protons in an atom, which defines the element. 2) Isotopes are atoms of the same element that have different numbers of neutrons, giving them different mass numbers. 3) The mass number counts both protons and neutrons in an atom. Atomic symbols indicate the mass number and atomic number.

1. The Atom: Atomic Number , Mass Number and Isotopes LecturePLUS Timberlake

2. Atomic Theory Atoms are building blocks of elements Similar atoms in each element Different from atoms of other elements Two or more different atoms bond in simple ratios to form compounds LecturePLUS Timberlake

3. Subatomic Particles Particle Symbol Charge Relative Mass Electron e - 1- 0 Proton p + 1+ 1amu Neutron n 0 1amu LecturePLUS Timberlake

4. Location of Subatomic Particles 10 -13 cm electrons protons neutrons 10 -8 cm LecturePLUS Timberlake nucleus

5. Atomic Number (Z) Counts the number of protons in an atom LecturePLUS Timberlake

6. Atomic Number on the Periodic Table 11 Na LecturePLUS Timberlake Atomic Number Symbol

7. All atoms of an element have the same number of protons 11 Na LecturePLUS Timberlake 11 protons Sodium

8. Learning Check AT 1 State 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

9. Solution AT 1 State the number of protons for atoms of each of the following: A. Nitrogen 2) 7 protons B. Sulfur 2) 16 protons C. Barium 3) 56 protons LecturePLUS Timberlake

10. Number of Electrons An atom is neutral The net charge is zero Number of protons = Number of electrons Atomic number = Number of electrons LecturePLUS Timberlake

11. Mass Number (A) Counts the number of protons and neutrons in an atom LecturePLUS Timberlake

12. Atomic Symbols Show the mass number and atomic number Give the symbol of the element mass number 23 Na sodium-23 atomic number 11 LecturePLUS Timberlake

13. More Atomic Symbols 16 31 65 O P Zn 8 15 30 8 p + 15 p + 30 p + 8 n 16 n 35 n 8 e - 15 e - 30 e - LecturePLUS Timberlake

14. Isotopes Atoms with the same number of protons, but different numbers of neutrons. Atoms of the same element (same atomic number) with different mass numbers Isotopes of chlorine 35 Cl 37 Cl 17 17 chlorine - 35 chlorine - 37 LecturePLUS Timberlake

15. Learning Check AT 2 Naturally occurring carbon consists of three isotopes, 12 C, 13 C, and 14 C. State the number of protons, neutrons, and electrons in each of these carbon atoms . 12 C 13 C 14 C 6 6 6 #P _______ _______ _______ #N _______ _______ _______ #E _______ _______ _______ LecturePLUS Timberlake

16. Solution AT 2 12 C 13 C 14 C 6 6 6 #P __6___ _ 6___ ___ 6 ___ #N __ 6 ___ _ _ 7 ___ ___ 8 ___ #E __6___ _ 6___ ___ 6 ___ LecturePLUS Timberlake

17. Learning Check AT 3 An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 2) 35 3) 65 B. Number of neutrons in the zinc atom 1) 30 2) 35 3) 65 C. What is the mass number of a zinc isotope with 37 neutrons? 1) 37 2) 65 3) 67 LecturePLUS Timberlake

18. Solution AT 3 An atom of zinc has a mass number of 65. A. Number of protons in the zinc atom 1) 30 B. Number of neutrons in the zinc atom 2) 35 C. What is the mass number of a zinc isotope with 37 neutrons? 3) 67 LecturePLUS Timberlake

19. Learning Check AT 4 Write the atomic symbols for atoms with the following: A. 8 p + , 8 n, 8 e - ___________ B. 17p + , 20n, 17e - ___________ C. 47p + , 60 n, 47 e - ___________ LecturePLUS Timberlake

20. Solution AT 4 16 O A. 8 p + , 8 n, 8 e - 8 B. 17p + , 20n, 17e - 37 Cl 17 C. 47p + , 60 n, 47 e - 107 Ag 47 LecturePLUS Timberlake

21. Learning Check AT 5 An atom has 14 protons and 20 neutrons. A. Its atomic number is 1) 14 2) 16 3) 34 B. Its mass number is 1) 14 2) 16 3) 34 C. The element is 1) Si 2) Ca 3) Se D. Another isotope of this element is 1) 34 X 2) 34 X 3) 36 X 16 14 14 LecturePLUS Timberlake

22. Solution AT 5 An atom has 14 protons and 20 neutrons. A. It has atomic number 1) 14 B. It has a mass number of 3) 34 C. The element is 1) Si D. Another isotope of this element would be 3) 36 X 14 LecturePLUS Timberlake

23. Masses of Atoms A scale designed for atoms gives their small atomic masses in atomic mass units (amu) An atom of 12 C was assigned an exact mass of 12.00 amu Relative masses of all other atoms was determined by comparing each to the mass of 12 C An atom twice as heavy has a mass of 24.00 amu. An atom half as heavy is 6.00 amu. LecturePLUS Timberlake

24. Atomic Mass Listed on the periodic table Gives the mass of “average” atom of each element compared to 12 C Average atom based on all the isotopes and their abundance % Atomic mass is not a whole number LecturePLUS Timberlake Na 22.99

25. Learning Check AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium __________ B. aluminum __________ C. lead __________ D. barium __________ E. iron __________ LecturePLUS Timberlake

26. Solution AT6 Using the periodic table, specify the atomic mass of each element (round to the tenths place): A. calcium _40.1 amu _ B. aluminum _27.0 amu _ C. lead _ 207.2 amu _ D. barium _137.3 amu_ E. iron _55.8 amu__ LecturePLUS Timberlake

27. Atomic Mass of Magnesium Isotopes Mass of Isotope Abundance 24 Mg = 24.0 amu 78.70% 25 Mg = 25.0 amu 10.13% 26 Mg = 26.0 amu 11.17% Atomic mass (average mass) Mg = 24.3 amu LecturePLUS Timberlake Mg 24.3