1. Atomic Structure
Part 2

2. 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

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

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

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

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

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

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

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

10. What are isotopes?

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

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

13. 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

14. 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

15. 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

16. 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-35
Chlorine-37

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

18. 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

19. Why does chlorine has a nucleon number of 35.5

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

21. 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

22. Practice Time
Part 3 Worksheet 2

23. Electrons Arrangement In Atoms

24. 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.

25. Electronic Structure

26. 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

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

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

29. 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

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

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

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

33. Summary

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

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

36. 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

37. Any Questions

38. Practice Time
Part 3 Worksheet 2