O-Level Chemistry Video – Group VII Trends in The Periodic Table


The topic on The Periodic Table is a very important topic in GCE O-Level Chemistry examinations. Besides the general characteristics and trends of The Periodic Table, students are required to know the properties of elements in Group I, Group VII, Group 0 as well as the Transition Metals.

Today, we will take a look at the properties of Group VII elements which are also known as the Halogens.

  • Exists as non-metals
  • Exists as diatomic molecules i.e. F2, Cl2, Br2, I2
  • Low MP & BP
  • Coloured
  • Undergoes Halogen Displacement Reaction (a redox reaction)
  • Strong oxidising agents

In the examination, you will also be asked to describe how the physical properties and chemical properties of halogens change going down the group.

Let’s take a look at a video on the Trends in Group VII Halogens of The Periodic Table and how the concept is being tested in examination. Download your printable summary for your easy reference here. 

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below.

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Direct link: https://youtu.be/trMsivt9wsY

 

 

 

 

 

O-Level Chemistry: Question on Isotopes


Most elements occur naturally as mixtures of isotopes with different relative abundances.

Hence, the relative atomic mass of an element (as seen in The Periodic Table) is the weighted average of the mass number of the isotopes according to their relative abundance.

In the previous blogpost, you have watched the video on Isotopes and how we calculate the relative atomic mass of an element.

Let’s put our knowledge into solving an examination-based question.

Question:

Naturally occurring gallium, Ga, has two isotopes of mass numbers 69 and 71 respectively. Given that the relative atomic mass of Ga to be 69.7, calculate the percentage abundance of each isotopes of gallium.

Suggested Solution:

Let the percentage abundance of gallium-69 be x mol.

The percentage abundance of gallium-71 will then be (100 – x) mol.

Relative atomic mass of Ga = 69x + 71(100 – x) / 100 = 69.7

69x + 7100 – 71x = 6970

x = 65%

Percentage abundance of gallium-69 = 65%

Percentage abundance of gallium-71 = (100-65) = 35%

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below. Feel free to share this blog post with your friends.

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O-Level Chemistry Video – Isotopes


In this video, you will understand the meaning of Isotopes and how this concept is tested in examination.

I hope you find the content easy for your understanding and if you have any questions, leave me a comment below.

Subscribe to my blog to receive 2 updates per month sent to your email! 

Direct link: https://youtu.be/T7GF9bb3Ez0

Isotopes is a very important concept in the topic of Atomic Structure.

It is defined as atoms of the same element with the same number of protons and electrons, but with different numbers of neutrons.

Since chemical reactions involve only on the electrons (specifically the valence or outermost shell electrons) and not the neutrons, isotopes have similar chemical properties.

E.g. Both chlorine-35 and chlorine-37 react with sodium to produce sodium chloride.

Physical properties of substances are affected by mass. Since isotopes have different masses, therefore, they have different physical properties.

E.g. Hydrogen-1 has a slightly higher boiling point and density than hydrogen-1.