Atomic Structure

• What are the three subatomic particles that make up an atom?

  Protons, neutrons, electrons
• Protons have a relative mass of 1 and a relative charge of +1
• Neutrons have a relative charge of 0 and are located in the nucleus.
• What is the relative mass of an electron?

  1/1840
• The atomic number of an atom is the number of protons
• What is the mass number of an atom?

  Protons + neutrons
• Match the term with its definition:

  Atomic number ↔️ Number of protons

  Mass number ↔️ Protons + neutrons

  Isotopes ↔️ Same protons, different neutrons
• Why do isotopes have the same chemical properties?

  Same electron configuration
• In a chemical symbol, the atomic number (Z) is the bottom number and the mass number (A) is the top number.
• The number of protons in an atom equals its atomic number.
• How is the number of neutrons in an atom calculated?

  Mass number - atomic number
• In an ion, the number of electrons is the atomic number minus the charge.
• Stages in a Time of Flight (TOF) mass spectrometer

  1️⃣ Ionisation

  2️⃣ Acceleration

  3️⃣ Separation of ions

  4️⃣ Detection
• What is electron impact ionisation used for in TOF mass spectrometry?

  Forming 1+ ions
• In electrospray ionisation, particles gain a proton as they leave the needle
• What does the acceleration stage in TOF mass spectrometry ensure?

  Same kinetic energy
• In the separation stage, lighter ions travel faster than heavier ions.
• At the detector in a TOF mass spectrometer, positive ions gain an electron
• What is the size of the current at the detector proportional to?

  Abundance of the ion
• The entire TOF mass spectrometer is kept under vacuum to prevent ions from colliding with air molecules.
• What is the formula for kinetic energy (KE) in terms of mass (m) and velocity (v)?

  $KE =$$\frac{1}{2}mv^{2}$
• Velocity (v) can be calculated using the formula v = d / t where d is distance and t is time.
• The Avogadro constant (L) is the number of ions in a sample with the same mass in grams as the relative isotopic mass.
• Match the ion with its mass in kg:

  ⁴⁰K⁺ ↔️ 6.642 x 10⁻²⁶ kg

  ¹⁰⁸Ag⁺ ↔️ 1.793 x 10⁻²⁵ kg

  ¹⁹F⁻ ↔️ 3.155 x 10⁻²⁶ kg
• What does the length of the flight tube in a TOF mass spectrometer represent?

  Distance ions travel
• When calculating the time of flight ratio, relative isotopic masses can be used because the conversion factor cancels out.conversion
• What is displayed in a mass spectrum?

  Relative abundance vs m/z
• In a mass spectrum of magnesium, ²⁴Mg generates the largest peak because it is the most abundant isotope.
• The relative atomic mass of magnesium is 24.3
• What is the time of flight of a ⁸¹Br⁺ ion if a ⁷⁹Br⁺ ion has a time of flight of 2.055 x 10⁻⁵ s?

  2.081 x 10⁻⁵ s
• The equation relating mass and time of flight in a time of flight mass spectrometer is m₁/t₁²
• What does a mass spectrum plot against relative abundance?

  m/z ratio
• The peaks in a mass spectrum correspond to different isotopes of an element.
• Which isotope of magnesium is the most abundant in its mass spectrum?

  ²⁴Mg
• The sample in a mass spectrometer must be ionised
• Match the term with its definition:

  Isotopic mass ↔️ Mass of an isotope relative to ¹²/₁ the mass of ¹²C

  Relative atomic mass ↔️ Weighted average mass of all isotopes relative to ¹²/₁ the mass of ¹²C
• Where in the periodic table is the relative atomic mass of an element found?

  Top number
• What is the equation for calculating relative atomic mass using isotopic masses and abundances?

  A_r = \frac{\sum (\text{mass} \times \text{abundance})}{\text{total abundance}}</latex>
• The relative atomic mass of sulfur calculated from its isotopes is 32.09.
• How is the denominator in the relative atomic mass calculation determined when using percentage abundances?

  100