1. Mass Spectrometer

2. Atomic Number Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element. Element# of protonsAtomic # (Z) Carbon66 Phosphorus15 Gold79

3. Mass Number Mass number (A) is the number of protons and neutrons in the nucleus of an isotope. Mass # = p + + n 0 Nuclidep+p+ n0n0 e-e- Mass # Oxygen -10 -3342 - 3115 8818 Arsenic753375 Phosphorus153116

4. Isotopes Isotopes are atoms of the same element having different masses due to varying numbers of neutrons. IsotopeProtonsElectronsNeutronsNucleus Hydrogen–1 (protium) 110 Hydrogen-2 (deuterium) 111 Hydrogen-3 (tritium) 112

5. E Mass Number Atomic Number Charge (if ion) A Z ISOTOPE NOTATION Symbol of Element

6. EXAMPLE How many protons, neutrons and electrons are found in an atom of 133 55 Cs Atomic number = protons and electrons There are 55 protons and 55 electrons Mass number = sum of protons and neutrons 133 – 55 = 78 There are 78 neutrons

7. HHydrogen 1 1 H-1 or “hydrogen one atom”

8. Na Sodium 23 11 1+ Na-23 ion or “Sodium 23 ion”

9. Oxygen O 15 8 2- O-15 ion or “oxygen 15 ion”