Dot- and- cross diagrams for simple covalent molecules

I was doing some research online today, when I chanced upon the GCSE Chemistry syllabus. You can take a look here. In the part on covalent bonding, the syllabus states that

Students should be able to: draw dot and cross diagrams for the molecules of hydrogen,chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane.........
When I saw this, my first thought was that students taking this exam should really score on questions on drawing dot and cross diagrams of molecules (note, under ionic compounds, this syllabus include other compounds which dot and cross diagram students need to know). The syllabus has specifically mentioned drawing these eight covalent molecules. Just practice drawing these many times, and you will score on this question.

Well, I have previously wrote a few blog posts detailing how to draw the dot- and- cross diagrams. You can find them here:
Drawing dot and cross diagrams (showing all electrons)
Drawing dot and cross diagrams (showing outermost electrons)

For the O level syllabus that Singapore students sit for, please note that you are not only restricted to drawing these eight molecules.

I have created two videos on drawing the dot and cross diagrams for these eight molecules, namely hydrogen,chlorine, oxygen, nitrogen, hydrogen chloride, water, ammonia and methane. One video shows the dot and cross diagrams with the outermost electrons only and another shows all the electrons.

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Electronic Configuration Summary and Quiz App- Now available on Google Play

I would like to share a new app now available on Google Play store, available for download for free here.

This App teaches both how to find the electronic configuration of particles i.e. atoms, cations or anions. In addition, examples are also included to reinforce the notes.

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Find number of electrons - Notes and Quiz

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The redox chapter for O level is one that involves mainly application. In this Redox Quiz App, we are doing exactly that --- application. You will be given an equation, and determine whether which species is being oxidized or reduced; whether it is an oxidising or reducing agent. What's more, you get to choose what you want to test yourself on.

This App is now avaliable for download here.

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Ethalpy Change App - Exothermic or Endothermic

The enthalpy change chapter is a relatively short one, covering the differences between exothermic and endothermic reactions.

In this App that I have created, you will be given equations, reactions, and description. From there, you will decide whether it is an exothermic or endothermic reaction. This App is written based on the O Level Chemistry syllabus, and would be a handy tool for you to test your knowledge of the heat of reaction chapter on the GO.

The App is available for download on Google Play store here.

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Organic Chemistry App - Alkanes, Alkenes, Alcohols and Carboxylic acids

Want to know how well you know the organic chemistry chapter?

To test your basic knowledge on these homologous series (i.e. alkanes, alkenes, alcohols and carboxylic acids), I have created two new Apps available for download at Google Play:

Each App consists of a number of questions, with answers. In each question, there is a short description, and one is supposed to determine the homologous series which best fits the description. Going through these questions, will reinforce the key concepts tested in the O level Organic Chemistry.

We usually have some small pockets of time available. And many of us make use of them by "looking" at our smart phones. What do you usually do when you "look" at your smart phone? I have a suggestion. Why not revise some topics that you have learnt? I have created a number of Apps which can allow you to revise small parts of your Chemistry syllabus quickly. You can find them here