2. Isotopic Abundance

3. Reminder: bring a calculator to class

4. Isotopes & Radioisotopes Isotopes have same number of protons (atomic #) and different numbers of neutrons and therefore different masses Isotopic abundance is the percentage of a given isotope in a sample of an element. Mass spectrometer is used to determine the mass and abundance of isotopes

5. Radioisotopes are isotopes that have unstable nucleus and undergo radioactive decay. Radioactive decay is the spontaneous disintegration of unstable isotopes to emit nuclear radiation such as alpha particle, beta particle and gamma ray

6. Nuclear radiation Particles emitted from nucleus of radioisotopes Alpha particle – a positively charged particle with the same structure as the nucleus of a helium atom Beta particle – a negatively charged particle identical to an electron Gamma ray – a high-energy electromagnetic radiation

7. Let’s consider the following question: if 12 C makes up 98.89% of C, and 13 C is 1.11%, calculate the average atomic mass of C: Mass from 12 C atoms 12 x 0.9889 Mass from 13 C atoms + 13 x 0.0111 + 11.8668 0.1443+= 12.01 Isotopic abundance

8. Mass from 35 ClMass from 37 Cl+ 35 x 0.755337 x 0.2447 + 26.43559.0539+ = 35.49 Mass from 39 KMass from 41 K+ 39 x 0.931041 x 0.0690 + 36.3092.829+= 39.14 = 39.99 Mass from 40 ArMass from 36 Ar+ Mass from 38 Ar+ 40 x 0.996036 x 0.0034 + 38 x 0.0006 +39.840.1224+ 0.0228+