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

4. Recap Atom is a particle which is electrically neutral No. of protons = No. of electrons An atom consists of 3 subatomic particles: 1) Protons 2) Neutrons 3) Electrons

5. Recap Structure of an atom Relative charges and approximate relative masses of protons, neutrons and electrons + Electrons Nucleus Protons and Neutrons

6. One hydrogen atom weighs as much as 1836 electrons Found around the nucleus. 1/1836 -1 Electron Mass is the same as that of a hydrogen atom Found in the nucleus of the atom 1 0 Neutron Mass is the same as that of a hydrogen atom Found in the nucleus of the atom 1 +1 Proton Remarks Relative Mass Charge Particle

7. Recap Symbol of an atom Chemical Symbol Nucleon Number Proton Number

8. Recap Proton number (atomic number) The number of protons in an atom For an atom, no. of protons = no. electrons

9. Recap Nucleon number (mass number) = no. of protons + no. neutrons No. of Neutrons = Nucleon number – Proton number

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

11. Today’s Menu What are isotopes Electrons arrangement in atoms Electronic structure Outermost electrons The Periodic table

12. What are isotopes?

13. What are isotopes Isotopes: Atoms of the same element having the same number of protons but different number of neutrons

14. What are isotopes Isotopes: Same number of protons (atomic number) Different number of neutrons Different number nucleon number Same number of electrons

15. Examples of isotopes Three isotopes of hydrogen 1) Hydrogen Number of proton: 1 Number of neutrons: 0 Nucleon number: 1 Number of electron: 1 Hydrogen-1

16. Examples of isotopes Three isotopes of hydrogen 2) Deuterium Number of proton: 1 Number of neutrons: 1 Nucleon number: 2 Number of electron: 1 Hydrogen-2

17. Examples of isotopes Three isotopes of hydrogen 3) Tritium Number of proton: 1 Number of neutrons: 2 Nucleon number: 3 Number of electron: 1 Hydrogen-3

18. Examples of isotopes Two isotopes of Chlorine Number of proton: 17 Number of neutrons: 18 Nucleon number: 35 Number of electron: 17 Number of proton: 17 Number of neutrons: 20 Nucleon number: 37 Number of electron: 17 Chlorine-37 Chlorine-35

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

20. What are isotopes Isotopes: All isotopes of the same element have the same chemical properties but small differences in physical properties There are two types of isotopes (i) Radioactive (ii) Non-radioactive

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

23. Why does chlorine has a nucleon number of 35.5 75% of all chlorine atoms have a mass of 35 25% of all chlorine atoms have a mass of 37 Average mass of one chlorine atom = = 35.5

24. Practice Time Part 3 Worksheet 2

25. Electrons Arrangement In Atoms

26. Electrons Arrangement in Atoms Electrons move around the nucleus of the atom The electrons are held in shells since it is of opposite charge The attractive force between the positive charge on the nucleus and the negative charge on the electrons is called electrostatic force.

27. Electronic Structure

28. Electronic Structure The way the electrons are arranged is called its electronic structure Electrons are arranged in shells which are numbered from the nucleus onwards Each shell is capable of holding up to a certain number of electrons

29. Electronic Structure Electrons are arranged in shells which are numbered: 1, 2, 3, 4 from the nucleus onwards Octet 8 (for atoms with proton number 20) 3 Octet 8 2 Duplet 2 1 Name Maximum no. of electrons Shell no.

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

31. Electronic Structure To find the electronic configuration of an atom, we should Fill the electrons into the shell nearest to the nucleus first. This shell can take a maximum of 2 electrons Once this shell is filled, the electrons go to the next available shell which has a maximum capacity of 8 electrons, and so on

32. Electronic Structure Sodium, Electronic Configuration 2, 8, 1 1 st shell 2 nd shell 3 rd shell Na

33. Electronic Structure Carbon, Electronic Configuration 2, 4 1 st shell 2 nd shell C

34. Electronic Structure Its important to know the electronic structure and electronic configuration of the first 20 elements of the Periodic Table

35. Summary

36. Summary 1) Isotopes are atoms of the same element having the same number of protons but different number of neutrons 2) E lectrostatic force is the force between the positive charge on the nucleus and the negative charge on the electrons.

37. Summary Electrons are arranged in shells which are numbered: 1, 2, 3, 4 from the nucleus onwards Octet 8 (for atoms with proton number 20) 3 Octet 8 2 Duplet 2 1 Name Maximum no. of electrons Shell no.

38. Summary To find the electronic configuration of an atom, we should Fill the electrons into the shell nearest to the nucleus first. This shell can take a maximum of 2 electrons Once this shell is filled, the electrons go to the next available shell which has a maximum capacity of 8 electrons, and so on

39. Any Questions

40. Practice Time Part 3 Worksheet 2