1. Atomic Particles Proton p + Neutron n Electron e - Mass /kg1.672x10 -27 1.674x10 -27 9.109x10 -31 Charge/C1.602x10 -19 0 Relative mass 111/1800 negligible Relative charge +10

2. Atomic Structure

3. Important Numbers Mass number (A) is the total number of protons + neutrons in the nucleus 23 Na 11 Atomic number (Z) is the number of protons in the nucleus

4. Numbers of particles No. of p + = Atomic Number (Z) No. of e - = No. of p + (atom is uncharged) No. of n = Mass Number – Atomic Number (A)(Z) No. of n = No. of p + + n – No. of p +

5. 23 Na 11 11 p + (Atomic number Z) 11 e - (No. p + = No. e - ) 12 n (mass number – atomic number) A – Z 23 – 11 = 12 Numbers of particles

6. Isotopes 8 neutrons (14-6 = 8) 6 neutrons (12-6 = 6) 6 protons Isotopes are atoms of the same element with the same atomic number but different mass numbers

7. Isotopes of an element have the same chemical properties because they have the same Atomic Number, Z (same no. p+ & e - ) Isotopes have different Mass Number, A, so they have slightly different physical properties –Masses - more/less neutrons –Melting & boiling points – forces of attraction different strengths –Densities – atoms are the same size but different mass –Rate of diffusion Isotopes

8. Uses of Isotopes Some isotopes are radioactive Iodine-131 injected into bloodstream to detect tumors Iron-59 used to monitor redblood cell production in bone marrow Sodium-24 used to detect blood clots Ratio of carbon-12 to carbon-14 used to date objects – Carbon dating