Atomic Structure

Atomic Structure: 3 Factors Affecting Ionisation Energy

April 26, 2018 By Sean Chua Leave a Comment

Today we are going to take a look at the 3 Factors Affecting Ionisation Energy in atomic structure. We have looked at the formal definition of ionisation energy previously and it’s really important that you are comfortable with that first.

3 Factors Affecting Ionisation Energy

1. Size of the positive nuclear charge

As the nuclear charge increases, its attraction for the outermost electron increases and more energy is required to remove an electron.

This means that the ionisation energy increases.

2. Size of atom (distance of outermost electron from the nucleus)

As atomic size increases, the attraction of the positive nucleus for the negative electron decreases and less energy is required to remove an electron.

This means that the ionisation energy decreases.

3. Screening (shielding) effect of inner shell electrons

The outermost electron is screened (shielded) from the attraction of the nucleus by the repelling effect of the inner electrons.

As shielding increases, the attraction of the positive nucleus for the negative electron decreases and less energy is required to remove an electron.

This means that the ionisation energy decreases.

Test Yourself NOW!

Let us take a look at a modified multi-choice question taken from GCE A-Level Higher 2 (H2) … Continue reading ...

Atomic Structure: 3 Rules of Writing Electronic Configurations of Atoms

March 29, 2018 By Sean Chua Leave a Comment

Today, we will look into the 3 Rules of Writing Electronic Configurations of Atoms in the topic of Atomic Structure.

Let’s look at some fundamentals of an atom first.

Electrons do not travel in fixed orbits around the nucleus i.e. they are not localised in fixed orbits. Instead, they travel in a region of space around the nucleus called an atomic orbital.

An atomic orbital is a region of space round the nucleus in which the probability of finding a particular electron in a free atom is the greatest. Some would say roughly about 98% chance of finding an electron.

Electrons can occupy four types of orbital, which differ from each other in terms of shape and in their orientation in space. They are called s, p, d and f orbitals. Students in Singapore taking the JC1 JC2 GCE A-Level H2 Chemistry Exam Syllabus Code 9729 are required to draw and describe the shapes of s, p and d orbitals accurately. I have blogged about this with a YouTube Video previously. If you have missed out on that, you can view them HERE and HERE. In my JC2 H2 Chemistry Tuition Class, i noticed … Continue reading ...

Atomic Structure: Ionisation Energy Video Tutorial

April 12, 2017 By Sean Chua Leave a Comment

Today, we are going to discuss a very important concept in Atomic Structure and Chemical Bonding, known as Ionisation Energy.

We will start by looking at First Ionisation Energy, 1^st IE which allows you to deduce the Second Ionisation Energy, 2^nd IE and more.

You will also understand how to determine the maximum number of ionisation energies of an element in the Periodic Table.

First Ionisation Energy, 1^st IE

It is defined as the amount of energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of singly charged gaseous cations.

It can be represented by the following equation: X (g) → X⁺ (g) + e^– ∆H₁ = 1^st ionisation energy = +ve

Second Ionisation Energy, 2^nd IE

It is defined as the amount of energy required to remove 1 mole of electrons from 1 mole of singly charged gaseous cations to form 1 mole of doubly charged gaseous cations.

It can be represented by the following equation: X⁺ g) → X²⁺ (g) + e^– ∆H₂ = 2^nd ionisation energy = +ve

All the ionisation … Continue reading ...

Atomic Structure: Shapes of Atomic Orbitals (including d orbitals)

February 17, 2017 By Sean Chua Leave a Comment

From the survey of my weekly JC1 and JC2 A-Level H2 Chemistry Tuition Classes, i realised that some students face challenges in drawing the Shapes of Atomic Orbitals in their Junior Colleges (JCs) lectures as well as school tutorials. In fact, it is very easy to draw them if you understand the concepts behind these Atomic Orbitals.

Atomic Orbital is basically a region of space around the nucleus in which the probability of finding a particular electron is the greatest i.e. about 98% chance of finding an electron.

Electrons can occupy four types of orbitals (s, p, d and f orbitals) that differ from each other in shape and in their orientation in space.

For Cambridge A-Level H2 Chemistry syllabus (refer to Singapore Examination & Assessment Board), you will only be tested on drawing the shapes of:

s orbitals: spherical shape
p orbitals: dumb-bell shape
d orbitals: 5 different types of orbitals (tested in the Year 2017 new syllabus code 9729)

At the end of this video, you will learn the strategy to draw the s, p and d atomic orbitals effectively.

Subscribe to my blog to receive 2 updates per month sent to your email! … Continue reading ...

Atomic Structure: Ionisation Energy

April 9, 2014 By Sean Chua Leave a Comment

Topics of Discussion: Atomic Structure – Ionisation Energy

Today, we are going to discuss on a very important concepts in Advanced Chemistry (such as the Cambridge Singapore JC A-Level H2 Chemistry and IB HL Chemistry) known as Ionisation Energy. I am currently teaching students in our JC1 A-Level H2 Chemistry Tuition classes the said concept.

Let’s hit the road and get started by defining the term (NOTE that you will be asked to define it in your written examination). We normally will start by asking you to define the first ionisation energy.

First ionisation energy of an element is defined as the amount of energy required to remove one mole of electron from each atom in a mole of gaseous atoms producing one mole of gaseous cations.

(Do note the words in italics which is what your examiner will be looking out for.)

An equation can be used to represent the first ionisation energy:

X(g) -> X⁺(g) + e^– ΔH₁ = 1^_st ionisation energy = +ve

Ionisation energies normally have positive values since energy is taken in to remove an electron i.e. endothermic.

The successive ionisation energies of an element increase with … Continue reading ...