2. Three fundamental particles in an atom Proton Electron Neutron

3. Proton Actual mass Relative mass (compare with proton) 1 Relative Charge (compare with proton ) +1 Position in atom Inside the nucleus Symbolp

4. Neutron Symbol Position in atom Relative charge Relative mass Actual mass n Inside the nucleus 0 1

5. Electron Symbol Position in atom Relative charge Relative mass Actual mass moving around the nucleus

6. Atomic structure e e e e e - - - - - - - - electron n (s) p (s) - - - - - - - - - - - - - - - nucleus

7. Atomic content of an atom no. of protons = 11 no. of electrons =11 no. of neutrons = 12 12n 11p Symbol

8. Atomic Content of  no. of protons = 6  no. of neutrons = 12 - 6 = 6  no. of electrons = 6  (An atom is neutral in charge)

9. Atomic Content of :  no. of protons = 7  no. of electrons = 7  no. of neutrons = 14 – 7 = 7

10. Atomic Content of  no. of protons = 6  no. of neutrons = 14 – 6 = 8  no. of electrons = 6

11. mass number atomic number Mass number = no. of p + no. of n atomic number = no. of protons

12. Isotopes Name of element : carbon carbon No. of protons : 6 6 No. of neutrons : 8 6 No. of electrons : 6 6 Isotopes are atoms of same elements which have the same atomic number but different mass number

13. Isotopes Burn in airCarbon dioxide Mass14 units12 units RadioactivityGive radiationDoes not give radiation (stable )

14. Extension : Isotopes ( For reference only ) 8n 6p nucleus 7n 7p nucleus A neutron in a nucleus of breaks into Electrons and energy are emitted to the surroundings Carbon -14 dating

15. Properties of isotopes  Same chemical properties  Different physical properties  e.g. mass b.p. and m.p. radioactivity

16. Actual mass VS relative mass Mass of 1atom Or 12 Which one is more convenience? Standard reference : 1 is equivalent to Relative mass

17. Simplified rule : We regard Relative mass of 1p = 1 Relative mass of 1n = 1 Relative mass of 1e = very small = 0

18. Relative mass of isotopes Relative mass 28 29 30 % abundance 92%4.7% 3.1% Do the three isotopes have the same chemical properties? Yes

19. It is difficult and not necessary to separate the isotopes in most of the reactions. Average relative mass of silicon is used to denote the mass of a silicon atom. Relative atomic mass of isotopes

20. Relative atomic mass of silicon ( P.5 e.g.1 ) Relative mass % abundance 282930 92% 4.7% 3.1% ( Relative ) Atomic Mass of silicon = 28 x 92% + 29 x 4.7% + 30 x 3.1% = 28.053 = 28.05

21. Ex1. Relative atomic mass of Chlorine Relative mass % abundance 3537 75.5%24.5% Atomic mass of Chlorine = 35 x 75.5% + 37 x 24.5% = 35.5