Summary Concept Map

Summary Concept Map

1. Atomic Structure

   • Atomic number is the number of protons in an atom
   • Atomic mass is the number of protons and neutrons in an atom combined
   • In a neutral/stable atom, the number of electrons is always the same as the number of protons

2. Nuclear Notation

   • A = the atomic mass (#p+n)
   • Z = the atomic number (p)
   • X = chemical symbol for element
   • Therefore, #neutrons can be found by subracting the atomic number (Z) from the atomic mass (A)

3. Charges

   • In nuclear notation, if an element has 1+, 2+ etc., written in the right hand corner, that means they are a cation and have lost one or two electrons
   • Comparatively, if the element displays a 1-, 2- etc., in the upper right hand corner, that means they are an anion and have gained 1 or 2 electrons

4. What are isotopes?

   • Isotopes are forms of an element that have the same number of protons but different numbers of neutrons.
   • Same: #protons, #electrons, atomic #, and chemical properties
   • Different: #neutrons, mass #, physical properties such as mass and density

5. Average Atomic Mass

   • A weighted average mass of the atoms across all the different isotopes
   • E.g., on average, chlorine's atom is 35.45 amu. This also takes into account the abundance of the different isotopes

6. Atomic Mass Units (amu)

   • The mass of a proton is approximately the mass of a neutron, which is approximately the mass of 2000 electrons.
   • 1 amu = 1.6605 x 10 ^24 g.

7. Relative Energies

   • F -orbital contains 14 electrons (7 sub orbitals)
   • D-orbital contains 10 electrons (5 sub orbitals)
   • P-orbital contains 6 electrons (3 sub orbitals
   • S-orbital contains 2 electrons

8. Rules for populating orbitals with electrons

   • Aufbau Principle: "Electrons enter the lowest available energy level."
   • Pauli's Exclusion Principle: "No two electrons can have the same four quantum numbers." Every orbital can hold a maximum of 2 electrons with opposite spins.
   • Hund's Rule: "When in orbitals of equal energy, electrons will try to remain unpaired."
     • • Each electron is in a seperate 2p orbital with the same spin. This is because more energy is required to pair up because like charges repel.

9. 3 ways to represent relative energies of electrons

   • SPDF electron configuration: shows number of electrons in shells and subshells
   • Condensed Spdf electron configuration: only the energy sublevels of valence electrons are shown
   • Orbital diagrams: show configurations of electrons in the orbitals

10. Steps for writing electron configuration

    • 1. Determine no. electrons present in the atom or ion.
    • 2. Add required no. electrons to each subshell in order of increasing energy (Aufbau Principle) until all have been allocated.
    • Remember the max. no. of electrons per subshell (Relative Energies)

11. Exceptions to the Aufbau Principle

    • Chromium - 24
    • Copper - 29
    • This is because half-filled and filled orbitals are more stable

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