## 17.1 Analysis of Isotopes using Mass Spectrometry This section explains how a mass spectrum can be used to determine the number of isotopes for a given element and their relative abundances. ### Interpreting a Mass Spectrum A mass spectrometer separates ions based on their mass-to-charge ratio ($m/z$). The resulting graph, a mass spectrum, provides two crucial pieces of information about the isotopic composition of an element. **1. Number of Isotopes** The number of distinct peaks that appear on the mass spectrum directly corresponds to the **number of isotopes** present in the sample. Each peak represents a different isotope with a unique mass. *Example:* - **Chlorine (Cl):** The mass spectrum of chlorine shows two peaks, indicating that there are two naturally occurring isotopes of chlorine ($^{35}\mathrm{Cl}$ and $^{37}\mathrm{Cl}$). - **Hydrogen (H):** The mass spectrum of hydrogen shows three peaks, corresponding to its three isotopes: protium ($^{1}\mathrm{H}$), deuterium ($^{2}\mathrm{H}$), and tritium ($^{3}\mathrm{H}$). **2. Relative Abundance of Isotopes** The height (or intensity) of each peak is proportional to the relative abundance of that specific isotope. A taller peak signifies a more abundant isotope, while a shorter peak indicates a less abundant one. This information is often expressed as a percentage. *Example:* - For chlorine, the peak for $^{35}\mathrm{Cl}$ is significantly taller than the peak for $^{37}\mathrm{Cl}$, indicating that $^{35}\mathrm{Cl}$ is the more abundant isotope (approximately 75.77%) compared to $^{37}\mathrm{Cl}$ (approximately 24.23%). The x-axis of the spectrum represents the **mass-to-charge ratio ($m/z$)**, and the y-axis represents the **relative intensity or abundance**. ### Basis of Separation in Mass Spectrometer The fundamental basis of separation in a mass spectrometer is the **mass-to-charge ratio ($m/z$)** of the ions. Ions are separated as they pass through magnetic and electric fields based on this ratio. The process involves several stages: 1. **Vaporization:** The sample is converted into gas. 2. **Ionization:** High-energy electrons knock off electrons from the atoms to form positive ions. 3. **Acceleration:** Ions are accelerated through an electric field. 4. **Deflection:** Ions are deflected by a magnetic field based on their $m/z$. 5. **Detection:** The detector records the ions hitting it. For more advanced analytical techniques, you can also explore .

17.1 How To Analyse A Number Of Isotopes And Their Relative Abundances Of Isotopes | Qualitative Analysis | Chemistry 12