UNIT 3 NOTES – Atomic Structure and the Periodic Table

1. UNIT 3 NOTES – Atomic Structure and the Periodic Table

2. UNIT 3 OBJECTIVES: 1) Describe the structure of the atom including: protons, electrons, and neutrons. 2) What are ISOTOPES? Explain why isotopes differ. 3) Diagram the Bohr Model of an atom. 4) Identify the position of groups, periods, and different chemical families on the periodic table.

3. OBJECTIVE 2: ● OBJECTIVE 2: What are ISOTOPES? Explain how ISOTOPES differ.

4. ISOTOPES: ● Atoms with the same number of protons, but different numbers of neutrons ● Isotopes of an element have the same atomic number, but different mass numbers

5. ISOTOPES: ● Nuclear Symbol or isotopic symbol – shows number of protons, neutrons and electrons in an atom

6. Diagram the nuclear symbol for: (A) lithium-7

7. Diagram the nuclear symbol for: (A) lithium-7

8. Diagram the nuclear symbol for: (A) lithium-7

9. Diagram the nuclear symbol for: (B) helium-4

10. Diagram the nuclear symbol for: (B) helium-4

11. Diagram the nuclear symbol for: (B) helium-4

12. Diagram the nuclear symbol for: (C) titanium-48

13. Diagram the nuclear symbol for: (C) titanium-48 Ti

14. Diagram the nuclear symbol for: (C) titanium-48 Ti 48 22

15. Atomic Mass ● Weighted average mass of the atoms in naturally occurring sample of an element ● Masses are based off of the atomic mass unit (amu) defined as one twelfth the mass of a carbon-12 atom

16. Atomic Mass Example #1 ● In nature carbon is composed of 98.89% 12C atoms and 1.11% 13C atoms. 12C has a mass of 12 amu and 13C has a mass of 13 amu. What is the average atomic mass of carbon?

17. Atomic Mass Example #1 ● In nature carbon is composed of 98.89% 12C atoms and 1.11% 13C atoms. 12C has a mass of 12 amu and 13C has a mass of 13 amu. What is the average atomic mass of carbon? Ave. atomic mass = (.9889)(12 amu) + (0.0111)(13 amu)

18. Atomic Mass Example #1 ● In nature carbon is composed of 98.89% 12C atoms and 1.11% 13C atoms. 12C has a mass of 12 amu and 13C has a mass of 13 amu. What is the average atomic mass of carbon? Ave. atomic mass = (.9889)(12 amu) + (0.0111)(13 amu) = 11.8668 amu + 0.1443 amu

19. Atomic Mass Example #1 ● In nature carbon is composed of 98.89% 12C atoms and 1.11% 13C atoms. 12C has a mass of 12 amu and 13C has a mass of 13 amu. What is the average atomic mass of carbon? Ave. atomic mass = (.9889)(12 amu) + (0.0111)(13 amu) = 11.8668 amu + 0.1443 amu = 12.0111 amu

20. Atomic Mass Example #2 ● In nature neon is composed of 90.5% 20Ne atoms, 0.2% 21Ne, and 9.3% 22Ne atoms. 20Ne has a mass of 20 amu, 21Ne has a mass of 21 amu, and 22Ne has a mass of 22 amu. What is the average atomic mass of neon?

21. Atomic Mass Example #2 ● In nature neon is composed of 90.5% 20Ne atoms, 0.2% 21Ne, and 9.3% 22Ne atoms. 20Ne has a mass of 20 amu, 21Ne has a mass of 21 amu, and 22Ne has a mass of 22 amu. What is the average atomic mass of neon? Ave. atomic mass =(.905)(21amu) + (.002)(21amu) + (.093)(22amu)

22. Atomic Mass Example #2 ● In nature neon is composed of 90.5% 20Ne atoms, 0.2% 21Ne, and 9.3% 22Ne atoms. 20Ne has a mass of 20 amu, 21Ne has a mass of 21 amu, and 22Ne has a mass of 22 amu. What is the average atomic mass of neon? Ave. atomic mass =(.905)(21amu) + (.002)(21amu) + (.093)(22amu) = 19.005 amu + .042 amu + 2.046 amu

23. Atomic Mass Example #2 ● In nature neon is composed of 90.5% 20Ne atoms, 0.2% 21Ne, and 9.3% 22Ne atoms. 20Ne has a mass of 20 amu, 21Ne has a mass of 21 amu, and 22Ne has a mass of 22 amu. What is the average atomic mass of neon? Ave. atomic mass =(.905)(21amu) + (.002)(21amu) + (.093)(22amu) = 19.005 amu + .042 amu + 2.046 amu = 21.093 amu

24. OBJECTIVES 1 & 2 REVIEW ● John Dalton – Dalton’s Atomic Theory stating atoms are solid, indivisible spheres ● J. J. Thomson – Thomson Model or “Plum Pudding Model” stating electrons are dispersed through a sphere of positive charge ● Ernest Rutherford – Rutherford Model stating atoms have a small, dense, positively charged nucleus surrounded by electrons