Ionization Energy Trend

Dhristi JEE 2022-24


Ionisation energy is the amount of energy required to remove an electron from a specific gaseous atom or ion. It applies to all the elements on the periodic table and not just the atoms that are gases at room temperature.

Trends and Periods

Looking at the periodic trend, as the students go from lithium over to neon, across the periodic table, the students can notice that there’s an increase in the ionisation energy. Lithium is positive 520 kilojoules per mole, and Beryllium’s goes up to 900 kilojoules per mole, and then again, in general, there’s an increase in ionisation energies going over to neon. That is because there’s also a relative increase in the effective nuclear charge. An ion is just an atom or a molecule with a charge, and it’ll have a charge if the protons are not equal to electrons. Neutrons are also composed of atoms but are neutral. The charge is given from protons or electrons, which is a net charge for an atom or molecule. A molecule’s just a cluster of atoms bonded together. The negative ions are more significant in the number of electrons than protons. So, for example, Hydrogen in its neutral state has one proton and one electron. Still, even if one of the electrons is taken away, then Hydrogen would have a positive charge, and essentially, it would just be, in its most common isotope, it would just be a proton by itself. And so, when it’s a positive ion where the number of protons is more than electrons, it is called Cations. Cation is just another word for positive ions. Likewise, we can have negative ions. For example, Fluorine. When fluorine gains an electron, it will have a negative charge. A negative ion is named an Anion. 

With the help of Ionisation, one can ionise different elements in the periodic table and turn them into cations. However, turning the element into gas is necessary before moving onto the electron.

Metals have low ionisation energy, whereas nonmetals have high ionisation energy. Ionisation energy will increase from left to right, and it will rise from the bottom to the top on the periodic table. Therefore, the lowest ionisation energy will be Francium, and the highest ionisation energy will be Helium. 

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FAQs (Frequently Asked Questions)

1. Explain ionisation energy?

We may think ionisation energy is given as a measure of the difficulty of removing the electron or the strength where an electron is bound. The higher the ionisation energy, the more difficult it becomes to remove an electron. Thus, ionisation energy is given as an indicator of reactivity. ionisation energy is essential because it is used to help in predicting the strength of the chemical bonds.

2. Mention the element which holds the highest ionisation enthalpy in the periodic table?

In the periodic table, the highest ionisation enthalpy is helium. It means 24.5874 eV or 2372.3 kJ/mol. This happens due to the reason helium holds two electrons in 1s orbit, which means the electron is very close to the nucleus and also unscreened, thus required very high energy to release from the nucleus.

3. What is ionisation enthalpy?

Ionisation enthalpy is defined as the energy needed to remove an electron from the gaseous atom, where the smaller the atom higher is the energy needed to remove the electron since there is a high attraction force on the outermost electron in the periodic table, from left to right, the size of atom decreases. Therefore, ionisation enthalpy increases, down the group size increases, so ionisation enthalpy decreases.

4. Define the term enthalpy?

Enthalpy is given as a property of thermodynamics, which can be explained as the sum of internal energy of the system and the product of pressure and volume of the same system. We can denote it by the symbol 'H'.

The above statement can be mathematically interpreted as given below:

H = U + PV.

5. Where do I find notes on Ionisation Energy?

To find a comprehensive list of notes related to ionisation energy, the students can refer to the Vedantu website. These reference study materials are made by people who are experts in their fields. The topic of ionisation energy is explained in detail by emphasisng on and referring to its periodic table and trends thoroughly. Vedantu offers a structured lesson plan, answer key and relevant question banks for free. This helps the students to comprehend the topic better and more easily. 

6. How do the notes on ionisation energy help me in preparing for my exams?

The notes on ionisation energy provided by Vedantu are well researched and thoroughly evaluated by experts in their fields. The functions of ionisation, its properties, the period tables and trends related to ionisation energy are equally explained and elaborated on Vedantu. The students can have access to these detailed notes by downloading the answer keys and revision notes in a pdf format which are available on Vedantu. Along with notes, the students can access the previous years’ question papers and determine the importance of the questions which will be asked in the examinations. 

7. What are the best tips to memorise the ionisation energy periodic table?

To memorise the ionisation energy periodic table, it is advisable to take the help of  flashcards. Using flashcards is effective in remembering the elements and periodic structures of each ionic property. By the method of show and tell normally used in flashcards, the students can retain a lot of information about ions and atomic structures as well as ionic properties and energy. Another way to memorise the ionisation energy periodic table is by learning it through mnemonics. Associating each element with a familiar word helps in remembering the information more easily. 

8. Do I have to learn the ionisation energy periodic table word by word?

Yes, it is important to learn about the ionisation energy periodic table to understand the related concepts which will be introduced later in the chapters. This basic understanding of the ionisation energy periodic table will act as a strong foundation in learning about atoms, ions, and other periodic elements. To know about the ionisation energy topic more thoroughly and study the concepts behind it, the students can download the detailed revision notes and answer keys which are available on the Vedantu website for free. 

9. Where can I get reference materials to study about ionisation energy?

Vedantu provides a list of reference books related to chemistry and its functions on its website. These reference materials are compiled in a manner which is suitable for students of different classes to refer to. They are done by experts and are cross referenced according to its relevance and accuracy. Vedantu has downloadable links in pdf format which makes the process of studying by the students in their own comfort zone much easier. These links direct to relevant notes, answer keys, objectives, diagrams and charts.