1. Topic 2 Atomic Structure

2. subatomic particles [40]
99.9% of mass of atom is located in nucleus, volume of electron cloud is 10,000 times greater than nucleus
particle
proton
neutron
electron
Relative mass 1
Relative charge +1 -1
Location
nucleus
Shells around nucleus

3. Mass number, atomic number, isotope [41]
Mass number (A) = sum of number of protons + neutrons
Atomic number (Z) = number of protons (equals number of electrons in atoms, not ions), gives identification of atom
Isotope = atoms with the same atomic number, different mass numbers (different number of neutrons)

4. Symbols for isotopes [41]
C-12
Carbon-12
126C
Exercises 2-4 page 46

5. Isotopes [42] Same chemical properties Different physical properties
Mass
Density
Rate of diffusion
Boiling and melting points

6. Radioisotopes [42-44] Unstable isotopes Uses Carbon dating (C-14)
Medical tracers (I-125 and I-131)
Radiation therapy (Co-60)

7. Mass spectrometer [47-49]
Instrument which separates particles according to their masses and records the relative proportions
Used in atomic mass determination

8. Mass Spectrometer [47]

9. Mass spectra [48] X- axis is relative mass relative mass = m/z
where m= mass and
z=charge

10. Atomic mass [48]
Defined as the weighted average of all the isotopes of each element.
Exercises 5-8 page 49

11. Knowledge of electron arrangements came about when studying the electromagnetic spectrum

12. Bohr model [52-53]

13. Bohr model [52-53]

14. Continuous vs. line spectrum [51]

15. Line spectra of hydrogen [52-53]
Evidence of Bohr model of atom
Spectrum of hydrogen is simplest – Why?
Divided into distinct series
Lyman
UV region
Balmer
Visible region
Paschen
Infrared region

16. Line spectra of hydrogen [52-53]

17. Ionization energy and electron arrangement [54-57]
Up to this point only main energy levels
Ionization energies prove existence of main energy levels and sublevels
Define ionization energy -
Successive ionization energies -

18. Ionization energy and electron arrangement [54-57]
main energy levels !

19. Ionization energy and electron arrangement [54-57]
energy sublevels !!

20. Atomic Orbitals [59-61]

21. Atomic Orbitals [59-61]

22. Atomic Orbitals [59-61]

23. Atomic Orbitals [59-61]

24. Electron arrangement [56-64]
Energy levels

25. Electron arrangement [56-64]
Energy sublevels –
Aufbau principle

26. Electron arrangement [56-64]
orbitals–
Hund’s rule
Pauli exclusion principle

27. Electron arrangement [56-64]
Electron configuration –

28. Electron arrangement [56-64]

29. Topic 2 practice
Starting with worked example page 56 then continue with exercises 9-26