Naming – ous vs ic

While naming ionic compounds using IUPAC involving multivalent metal ions the oxidation state or valency of the element is shown in brackets after the name of the metal using roman numerals. Example Iron (II) Sulfate = Fe2SO4, if you name the same compound using trivial naming system or the older naming system the compound is called Ferrous Sulfate.
Multivalent ions when named using the trivial system the metal with lower oxidation system always ends in -ous and the next higher oxidation number will end in -ic.
So Iron (III) Sulfate or Fe2(SO4)3 will be called Ferric Sulfate.
Cu+ = Cuprous ion
Cu2+ = Cupric ionĀ  and so on

 

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Ionic compounds and shapes

Ionic compounds do not have shape, on the other hand molecular compounds have a definite shape. Ionic compounds have a crystal structure, the inter ionic attraction being electrostatic the force of attraction is directed in space in a three dimensional area, in NaCl each sodium ion is surrounded by six chloride ions and each chloride ion is surrounded by six sodium ions effectively the positive charge is satiated by the negative charges surroundings it. If you look closely you would see that if the positive charge is placed at a point where the three axis intersect the chloride ions would be on either ends of the X, Y and Z axis. This potentially would lead to an FCC type of unit cell, and in each unit cell we would have 4 formula units of NaCl.

The formula of sodium chloride is represented as the simplest ratio in which the positive and negative ions combine to form a neutral molecule. Hence MgO and not Mg2O2. Every ionic compound would belong to one of the 7 crystal systems.
FCC represents face centered cubic unit cell. There are 4 formula units in one unit cell of NaCl, yet the formula is represented as a 1:1 ratio of positive to negative compound.

 

 

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Summer School

It is that time of the year again. Well if you did goof off during the year and lost a credit then I’m sure your reading this blog. I typically don’t think summer school is the right place to earn a credit, if you plan on pursuing your education in the field that you did goof off, then it is a big mistake. The program is so compressed and if you are not one of the smart Alec’s then you are in for a surprise. You may earn a credit but it may not really help you in your university. You will end up learning it anyway. So this would be a more practical approach to earn the credit in a regular school year.
However if you still need the credit to graduate there are a number of links on this site if you are pursuing chemistry this summer. The course codes should help go the the right page.
SCH3U = Grade 11 Chemistry
SCH4U = Grade 12 Chemistry

Bonding

A page on chemical bonding has been added to the site. I gives a fundamental idea of the concepts of bond formation, explained using the concept of stability, with respect to electronic configuration, octet, lowered potential energy and the ways it can be attained. The ideas of ionization energy, electron affinity, electro negativity, intra molecular forces, intermolecular forces and consequences on the properties of matter are dealt with. The topics are also relevant to CBSE