How do Atoms Bond?
This post will introduce the fourth topic of Prelim Chemistry, Bonding, and an introduction to ionic and covalent compounds.
- Investigate the differences between ionic and covalent compounds through:
- Using nomenclature, valency and chemical formulae (including Lewis dot diagrams)
- Examining the spectrum of bonds between atoms with varying degrees of polarity with respect to their constituent elements’ positions on the periodic table
- Modelling the shapes of molecular substances
Ionic vs Covalent Compounds
Ionic compounds are compounds with atoms that fully exchange electrons (an ionic bond) with each other while covalent compounds are compounds formed by atoms that share electrons between one another (a covalent bond). (Note that there exist more types of bonding that are kind of between these two). This video explains more about covalent and ionic bonds and introduces the concept of polarity.
Nomenclature for Ionic and Covalent Compounds
This video explores the nomenclature of ionic and covalent compounds. Recall that nomenclature refers to naming conventions.
Lewis Dot Diagrams
This video introduces Lewis Dot Diagrams and explains how to draw them. (Note that while you may see people using crosses instead of dots, use dots whenever you are asked to draw a Lewis Diagram)
You have probably used a molymod kit or some other molecular modeling kit in class. In these models, it is very obvious that atoms are not 2D, which drawings such as electron configuration diagrams and Lewis Dot Diagrams fail to convey.
In reality, some bonds require more space than others (such as double bonds over single bonds), and sometimes the valence electrons (electrons on the outermost shell) do not all get used in covalent bonding resulting in lone pairs (a pair of unbonded electrons). This is where molecular geometry comes in, this describes the shape of a molecule based on the number of bonds and lone pairs. After this, have a look at water compounds (H2O) and see if you can explain its molecular geometry.
This video explains some basics about molecular geometry and Valence Shell Electron Pair Repulsion Theory (VSEPR).