Compounds

This Chemistry lesson is titled Bonding in Polyatomic Ions and Compounds and will give a detailed explanation of the topic.

This is the first in a series of video lesson on d-block elements and their compounds. I look at the electronic configurations of the first row and try to explain the trend in their melting points. Minimizing electron repulsion is the most important consideration at play in these atoms and ions, but it is not the only one. This lesson is aimed at High School level and I only attempt to provide a simplified explanation. The following three points are perhaps worth adding: (1) the 4s orbital behaves as the outermost energy orbital - and as a result they nearly always lose a minimum of 2 electrons. (2) in addition to energy levels of orbitals, you need to factor in both their shape and closeness to one another - facilitating electron movements between them. (3) atomic orbitals can mix (hybridize) and at times the actual electronic configuration of the ions may be more complex than shown here.

Here I look at the roles of transition metals and their compounds in homogeneous and heterogeneous catalysis. I also briefly consider autocatalysis.

Many practice problems for how to calculate and determine oxidation numbers, often referred to as oxidation states. To figure out oxidation numbers for elements in a compound, we have to look on the periodic table and consult a list of rules. For neutral compounds, the oxidation numbers add up to zero. For polyatomic ions, the oxidation numbers add up to charge of the ion.

Transition metal salts appear in many different colours, while non-transition metal salts are mostly white. This second video, in a series on d-block elements and their compounds, explains the origin of that colour.