Topic 1

Topic 1

1. Definitions

   • ION- An atom or group of atoms with a charge due to a gain or loss of electrons
   • ISOTOPE- Atoms with the same amount of protons but different amount of neutrons, hence a different mass number
   • RELATIVE ATOMIC MASS- Average mass of an atom of an element relative to the mass of 1/12th of a Carbon-12 atoms
   • MASS NUMBER- The amount of protons and neutrons in the nucleus
   • ATOMIC NUMBER- The amount of protons in the nucleus
   • ORBITAL- A regions where electrons are likely to be found
   • IONISATION- The removal of an electron to gain a positively charged ion
   • FIRST IONISATION ENERGY- The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of positively charged ions
     • Mg(g) --> Mg+(g) + e-
   • PERIODICITY- Repeated patterns in physical and chemical properties across different periods

2. Mass Spectrometry

   • Mass spectrometry is used to create positively charged ions from a gaseous sample injected into it
   • 1) ATOMISATION- The element is turned into its gaseous form. The gas enters the mass spectrometer and is bombarded with high energy electrons.
     • 2) IONISATION- A filament current ionises the gas. The gas gains a positive charge since it loses an electron
       • 3) The positive ion accelerates, due to the electric field, towards a charged slit.
         • 4) The ion gets bent due to a magnetic field causing the ion to move in a circular path, whose radius depends on the mass of the ion.
           • 5) DETECTION- The detector enables the number of ions per particle mass to be determined
   • USES
     • Determine relative atomic mass of a compound
     • Structure of compounds
     • Measurement of 14C:12C radioactive dating of organic materials
     • Isotopic composition
     • Determine molecules in blood and urine

3. Electron Configuration

   • ENERGY LEVELS:
     • 1) Atoms are heated hence the electrons are given thermal energy
       • 2) The electrons move up to a higher energy level since they become excited.
         • 3) Due to the instability of a higher energy level the electron moves back down to ground state
           • 4) Whilst moving back down to ground state the electron releases electromagnetic radiation
   • Cr- 1s2 2s2 2p6 3s2 3p6 3d5 4s1
   • Cu- 1s2 2s2 2p6 3s2 3p6 3d10 4s1
   • This is due to the extra stability of a fully/half filled set of d-orbbitals

4. Trends in Ionisation Energies

   • Down a group
     • N- Despite nuclear charge increasing
       • A- Atomic radius increases in size
         • S- Shielding also increases meaning the outermost electron is further away from the nucleus
           • A- Overall attraction decreases down the group therefore less energy is required to remove the electron
   • Across a Period
     • N- Nuclear charge increases
       • A- Atomic radius decreases so the outermost electron is closer to the nucleus
         • S- Despite shielding staying the same
           • A- Overall attraction increases across a period therefore more energy is required to remove the electron
   • DIP 1- The s-sub shell is of lower energy than the p-sub shell. Therefore less energy is needed to remove the outer electron for group 3 atoms
   • DIP 2- Group 6 have a pair of electrons in its outermost shell, hence the electrons would repel so less energy is required to remove the electrons