1) Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. 2) Electrons are arranged in shells around the nucleus numbered 1, 2, 3, etc. The first shell can hold up to 2 electrons and subsequent shells can hold up to 8 electrons. 3) To find an element's electronic configuration, electrons are filled into the lowest available energy shell first.

1. A t o m i c S t r u c t u r e Part 2

3. Recap

10. Overview of topic Structure of Atoms Isotopes Electronic Arrangement Electronic Structure and the Periodic Table Ions Atomic Structure

12. What are isotopes?

19. What are isotopes 1 2 1 1 1 1 1 0 1 Electrons Neutrons Protons Number of Isotopes

21. Why does chlorine has a nucleon number of 35.5

22. Why does chlorine has a nucleon number of 35.5 In the periodic table, chlorine is denoted as

24. Practice Time Part 3 Worksheet 2

25. Electrons Arrangement In Atoms

27. Electronic Structure

30. Electronic Structure 1 st shell 2 electrons 3 rd shell 8 electrons (proton number 20) Nucleus 2 nd shell 8 electrons

35. Summary

39. Any Questions

40. Practice Time Part 3 Worksheet 2