Atomic Structure

• What is an isotope

  Elements with same number of protons, different number of neutrons
• What is an ion?

  When an atom loses/gains an electron.
• Ar/ Relative Atomic Mass

  average mass of an atom of an element in comparison to

  1/12th of an atom of carbon-12
• Mr/ relative molecular mass

  sum of all atomic masses of each element in the molecule
• TOF ionisation

  •Electrospray ionisation: Sample is dissolved and pushed through a nozzle at a high pressur. High voltage is added to it, causing particles to gain a H+ charge.

  •Electron Impact ioninsation: Sample is vaporised. An electron gun is fired at it, high energy electrons knock of the particles electrons, making them a +1 ion.
• TOF mass spectrometer

  •Acceleration: Positively charged ions are accelerated by an electric field. Lighter ions accelerate faster than heavier ions.

  •Ion drift: ions enter a region with no electric field and drift through it.

  •Detection: Lighter ions reach the negative detection plate before heavier ions. As they hit the plate, theres a flow of charg.
• Electron configuration

  
• First Ionisation Energy

  Minimum energy needed to remove 1 mole of electrons from 1 mole of atoms in a gaseous state. High ionisation means high attraction between electrons and nucleus.
• Factors affecting first ionisation energy

  •nuclear charge: more protons means stronger attraction for electrons

  •shielding: increase in electrons between nucleus and outer electrons means weaker attraction

  •distance from nucleus: distance weakens attraction
• Second ionisation energy

  Energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions.
• Trends in first ionisation energy

  •ionisation increases along a period: atomic radius decreases, number of protons increases, there’s a greater attraction to electrons

  •ionisation decreases down a group: atomic radius decreases and so does shielding, reducing electrostatic attraction