[S2] LESSON 45 : Chemistry Headstart L4 – Chemical Equation Writing Updates/Debrief

[S2 Maths + Science PMCians]

What we did in 2 hours:

This week we carried on with our Part 2 of Chemistry Headstart on Chemical Equations.


First we had a quick recap on how to determine the charge of ions based on their group number in the Periodic table. Then we move on to learn how to write the chemical formula and name of ionic and covalent compounds.

– charges of ions must balance in a chemical formula

– name of non-metal negative ions end with -ide

– name of polyatomic ions which carry oxygen end with -ate

– prefixes (e.g. mono, di, tri) are used to indicate the number of a given element present in covalent compounds


Next, we learnt about equation writing, which include balancing and writing the state symbols.

-Strategies for balancing chemical equations

1) calculation by atoms

2) calculation by ions

3) transfer of oxygen

4) balance everything before hydrogen/oxygen

5) fractions


– Solubility table (need this to determine the state symbol)

1) ALL group I, ammonium and nitrates are soluble in water

2) MOST sulfates and chlorides are soluble in water, except barium, lead & calcium sulfates and silver & lead chlorides

3) MOST carbonates and hydroxides are insoluble in water, except group I & ammonium carbonates and group I & some group II hydroxides


Finally, we learnt about acid/alkali reactions and practised to write balanced chemical equations with state symbols of these reactions.


Special Mention:

Next lesson, which is the last lesson of our headstart, we will be doing Physics Headstart on Lens.


See you soon! 🙂



Your friendly tutors,

The S2MA+SCI Team


Students can choose to attend any of the timeslots onsite in the respective outlets or live from home at the same timing. There will be both ONSITE and ONLINE audience for all classes. ONSITE and ONLINE students will be able to interact with one another and the tutor will be able to engage both audiences. Both platforms (onsite and online) will be carried out concurrently, ensuring that students in the physical classroom and those attending lessons via Zoom are taught exactly the same content, at the same time, by the same tutor.