Chapter 5

• What are electron shells made up of?

  Sub-shells & orbitals;

  
  

  Shells are divided into sub-shells;

  
  

  These sub-shells have diff numbers of orbitals

  
  

  Learn table

  
• What is the shell or energy level number called?

  The principal quantum number;

  
  

  Shells further from nucleus have a higher energy level

  
  

  Learn table

  
• What is meant by an orbital?

  A region within an atom that can hold up to two electrons, with opposite spins;

  
  

  An orbital can hold one or two electrons, but no more
• s-orbitals

  Spherical shape;

  
  

  (In an s-orbital the electron cloud is within the shape of a sphere)

  
  

  There's one s-orbital.

  
  

  Can hold up two electrons
• p-orbitals

  Dumb-bell shape;

  
  

  (In a p-orbital, the electron cloud is within the shape of a dumb-bell)

  
  

  As with an s-orbital, one orbital can contain one or two electrons.

  
  

  There are three separate p-orbitals at right angles to one another. These orbitals are referred to as Px, Py and Pz.

  
  

  There are three p-orbitals.
• How many electrons are in each shell?

  Shell 1 - 2 electrons;

  
  

  Shell 2 - 8 electrons

  
  

  Shell 3 - 18 electrons

  
  

  Shell 4 - 32 electrons
• Electrons pair with opposite spins.

  Electrons are negatively charged and repel one another.

  
  

  Electrons have a property called spin - either up or down;

  
  

  An electron is shown as an arrow indicating its spin, either up or down;

  
  

  The two electrons in an orbital must have opposite spins;

  
  

  The opposite spins help to counteract the repulsion between the negative charges of the two electrons.

  
  

  Electrons fill up orbitals with the same energy singly before they start pairing up (up arrows first)
• How can you represent electrons in orbitals?

  Using arrows and boxes;

  
  

  Each box represents an orbital;

  
  

  Each arrow represents an electron

  
• Electronic configuration


  The number of electrons an atom or ion has and how they are arranged
• What is the order of sub-shell filling?

  1s 2s 2p 3s 3p 3d 4s 4p

  
  

  The 4s sub-shell fills before the 3d sub-shell because 4s has a lower energy level but its still written after the 3d

  
• Sub-shell notation?

  E.g. 1s² 2s² 2p⁶

  
• Electronic configuration for ions?

  Just add or remove electrons from the highest energy sub-shell;

  
  

  4s electrons are first in and first out
• Shorthand electron configuration.

  Electron configurations can be expressed more simply in terms of the previous noble gas in the periodic table plus the outer electron sub-shells;

  
  

  MUST USE previous NOBLE GASES that the element is after

  
• What are the blocks of the periodic table?

  s-block, d-block, p-block, f-block.

  
• 4s sub-shell

  The 4s sub-shell fills before the 3d sub-shell.

  
  

  The 4s sub-shell also empties before the 3d sub-shell.
• What is ionic bonding?

  Ionic bonding is the electrostatic attraction between positive and negative ions (oppositely charged ions)

  
  

  It holds together cations and anions in ionic compounds;
• Ionic bond

  An electrostatic attraction between two oppositely charged ions
• Each ion attracts oppositely charged ions in all directions. What is the result of this?

  A giant ionic lattice
• A dot a cross diagram for ionic compounds?

  Shows the arrangement of electrons in an atom or ion;

  
  

  The square brackets show that the charge is spread over each ion and the ions are seperate entities;

  
  

  Only outer electrons are shown

  
• Define Giant ionic lattice?

  Repeating pattern of oppositely charged ions;

  
  

  Compounds of metals & non-metals
• Giant ionic lattice: examples?

  NaCl;

  
  

  CaO;

  
  

  MgBr₂

  
• Giant ionic lattice: particles it contains?

  Ions
• Giant ionic lattice: how particles are bonded together?


  Strong ionic bonds;

  
  

  Attraction between oppositely charged ions
• Giant ionic lattice: Mpt & Bpt?

  High;

  
  

  Giant ionic lattices are held together by strong electrostatic forces;

  
  

  Strong electrostatic attraction between oppositely charged ions;

  
  

  High temp needed to provide sufficient energy to overcome the attraction

  
  

  Almost all ionic compounds are solids at room temperature.
• Giant ionic lattice: Solubility?

  Ionic compounds tend to dissolve in water;

  
  

  Polar water molecules are attracted to the charged ions;

  
  

  Water molecules bond to the ions, weakening ionic bonding;

  
  

  Ionic bonds broken;

  
  

  Ions become surrounded by water molecules and break free from the lattice

  
  

  Solubility decreases as ionic charge increases;

  
  

  Solubility requires two main processes:

  The ionic lattice must be broken down.

  Water molecules must attract and surround the ions.
• Giant ionic lattice: electrical conductivity?

  Doesn't conduct electricity in the solid state: no mobile ions, ions not free to move

  
  

  Conduct electricity when molten or dissolved in water: mobile ions, ions are free to move
• What is covalent bonding?.

  Covalent bonding is the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms;

  
  

  Between non-metals
• What does covalent bonding occur in?

  Non-metallic elements like H2 and O2;

  
  

  Compounds of non-metallic elements like H2O and CO2;

  
  

  Polyatomic ions like NH4+
• Covalent bonding: Dot and cross diagrams

  There are single double and triple covalent bonds

  
• Covalent bonding: Dot and cross diagrams (special cases)

  
• What does the average bond enthalpy show?

  Measures the energy required to break a covalent bond;

  
  

  The stronger the bond is, the more energy is required to break it and so the greater the value of the average bond enthalpy
• Difference in bonding between covalent and ionic?

  Covalent:

  Attraction is localised;

  
  

  Acting solely between the shared pair of electrons and the nuclei of the 2 bonded atoms;

  
  

  Electrons are shared

  
  

  Ionic:

  Ion attracts oppositely charged ions in all directions;

  
  

  electrons are transferred
• What is the number of covalent bonds each atom can make?

  carbon forms 4 bonds

  
  

  nitrogen forms 3 bonds

  
  

  oxygen forms 2 bonds

  
  

  hydrogen forms 1 bond
• What is a dative covalent bond/coordinate bond?

  A shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only;

  
  

  When one atom donates both electrons to a bond;

  
  

  Its shown by an arrow pointing away from 'donor' atom
• Examples of dative covalent bonds?

  Ammonium ion;

  
  

  An ammonia molecule donates its lone pair of electrons to a H+ ion;

  
  

  Its shown by an arrow pointing away from 'donor' atom

  
• Formula of fluorides of non-metals: P, S, Cl

  
• What is

  expansion of the octet?This is possible from the n=3 shell onwards;

  
  

  when a d-sub shell becomes available for expansion
• What is the formula for how many electrons a shell holds?

  2n² (n is the shell number)
• Define orbital

  A region within an atom that can hold up to 2 electrons with opposite spins
• What are the 4 types of orbitals?

  s, p, d, f