Ionic Compounds

  • Ionic Bonding:
  • occurs between a metal and a non-metal
  • results in a positive cation (metal) and a negative anion (non-metal)
  • forms a salt, that is a lattice structured crystal that is more stable than the reactants
Electron Transfer Diagrams

Used to represent a reaction, showing the transfer of electrons
Reactants on the left, products on the right

Ionic Lattice:
ionic compounds form crystals, a lattice composed of positive and negatively charged atoms in a regular 3D structure. They are held together by strong electrostatic attraction between oppositely charged ions.
The atoms are packed in a regular repeating pattern. They form into the most stable arrangement with oppositely charged ions as close as possible and those with the same charge, as far away as possible.
Properties
  • Rigid as ions are tightly held
  • Does not conduct electricity- no free charged particles in solid state, however, in molten or aqueous they are able to as ions have become disassociated
  •  Brittle as pressure causes like charges to align, causing electrostatic repulsion between atoms and shattering of the compound
  • Will often dissolve forming an electrolyte. This is due to the water molecules being able to move between then ions and disrupt the bonds
  • Usually crystalline solids due to the close packed 3-D lattice
  •  High melt/boil point due to the strong attraction



Ionic Formulas:
Step1: Use the table of ions/electrovalencies to write down the required positive ion (first) and negative ion (second).
Step 2: Combine the positive ion with the negative ion in the ratio to produce no overall charge.
Step 3: If the ratio is 1:1 write the formula (do not include charges as they cancel out).
Step 4: If the ratio is not 1:1, use subscripts to indicate how many of each ion is required.
Note: Some elements form ions of different charges, so electrovalency must be specifies by placing charge into roman numerals

Example: Iron (II) Chloride contains the Fe2+ ion, formula is FeCl2
     Iron (III) Chloride contains the Fe3+ ion, formula is FeCl3
            Al3+ Cl2-  becomes Al2 O3
            Mg2+ Cl-  becomes  MgCl2
Common ions and their name

Naming Ionic Compounds:


1.         Metal listed first, full name
2.         Non-metal second, adding –ide if only one atom is present
3.         Determine lowest whole number ratio that gives net zero charge
4.         Use roman numerals to indicate which ion is being used


Examples:
Na2O is called sodium oxide (not sodium oxygen)
MgS is called magnesium sulphide (not magnesium sulfur)
MgSO4  is called magnesium sulfate (SO42-  is the sulfate ion)
Calcium Nitride Ca3N2
Calcium Nitrate Ca(NO3)2


Hydrated Ionic Compounds
Hydrated ionic compounds contain a fixed number of water molecules bonded within the ionic crystal structure for everyone unit of salt.

E.g. ZnCl2~8H2O  - Iron (II) Sulfate octahydrate

Comments

Post a Comment

Popular posts from this blog

Common Literary Techniques in Tim Winton's 'The Turning'

Common techniques in Winton’s The Turning . Most of these examples are taken from ‘Aquifer’. Direct, concrete images: ‘In the afternoon the blue bush plain was hazy with smoke and the dust churned up with bulldozers.’ While these descriptions are simple and clear ways of describing the real world, Winton often highlights aspects that explore and reveal key aspects of the ideas or characters he is exploring. For example, the ‘hazy’ and ‘churned up’ elements in this description highlight 2 things: 1) the confused and often conflicting feelings of the narrator as he reflects back on a time of emotional and hormonal turmoil (growing up); 2) the murky and muddled interaction between past and present.  There is a tension or irony here in that the descriptions seem so straightforward and clear that the memories are certain, solid, can’t be argued with, which is true.  And yet how one grapples with these memories, how one mixes them/reconciles them with the present is less
Read more

Covalent Compounds

Image
Covalent bonds form between non-metal atoms. In order to reach stability, non-metal atoms want to gain electrons due to high electronegativities, so instead of stealing electrons, as in  ionic bonding , or giving them away as  metals  do, non-metals share. How sweet, they are so kind. Atoms share electrons so that they have a full valence shell. Remember Nobel Gases won't form covalent bonds/molecules as they already have full valence shells. Discrete Covalent Molecules: Exist as individual molecules: CO 2 , H 2 O, C 6 H 12 O 6 , HCl Many are gases / liquids at room temperature Generally low melting/boiling point poor conductors of electricity - no free charged particles, unless dissolved in water like dissolves in like (polar molecules will dissolve in polar molecules, same as non-polar will in non-polar) Covalent Network Lattices: Exist as a 2 or 3D layer lattice where each atom os covalently bonded to other atoms. Their properties vary greatly due to variation in s
Read more