Among all of us who have studied bit much of physics and chemistry; must have heard the term called ionization energy or ionization energy trend. This term is denoted by Ei. Basically, ionization energy is the energy that is required to remove an electron which is loosely attached in the valance cell of a gaseous atom. So, it is clearly visible that the ionization energy is the measurement of the hardship required for removing an electron or the net energy by which an electron is covered. How much the ionization energy increases, it becomes more difficult to remove an electron. Therefore, ionization energy indicates the reactivity of the molecule. It holds a very important value in chemistry because it is very often used to calculate the strength of several chemical bonds. You might have a question in your mind that which element has the highest ionization energy? So, the answer is helium. Yes, helium is the element which has the highest ionization energy. While going through this informative we will let you know about some term regarding this topic such as how to calculate ionization energy, first ionization energy, electron affinity or electron affinity trend etc.
Substitute term: ionization potential, IP, IE
Unit: ionization energy is often Calculated in KJ/mol or electron volt (eV)
Ionisation energy at the periodic table
Ionization energy along with atomic radius, electronegativity, electro affinity and metallicity follow a trend according to the periodic table of elements.
- In general, if we move from the left side to right side of an element period or row whatever you can call it; ionization energy will increase. This thing happens because as we move across a period; atomic radius of a specific atom get decreased and that means an effective attraction exists between negatively charged electrons and positive nucleus. ionization value is minimum for the alkali metals which are on the left side of the table and maximum for the noble gases on the complete right side of the periodic table. It is needless to say that the noble gases have the loaded valance shell so, electron removal is highly resisted by them.
- Similarly, if we move from the top to bottom of the periodic table basically of an element of group; ionization energy get decreased. This happens because the principle quantum number of the outermost electron get increased moving across of a column. There will be a lot more protons in the lower elements of a column and that helps to attract the electron shells and makes them smaller and also the outer electrons get screened from the attractive force of the so-called nucleus. More electron orbital will be added as we move down of a group. So, the outermost electron maintains an increasing distance from the nucleus.
What are the first, second and subsequent ionization energy?
The total amount of energy that is required to remove the outermost valance electron of an atom which is neutral is called as the first ionization energy. Second ionization energy is required to remove the electron which is situated just after the outermost valance electron. For some obvious reason second ionization energy is always higher than the first ionization energy. Suppose removing an electron from the outer shell of an alkali metal atom is lot easier because it gives the meatal a stable condition. But removing the second electron becomes difficult because this electron exists in a particular shell which is closer and more tightly bound to the nucleus of the atom.
Important Points to be noted
- All of us have already known that ionization energy is the minimum amount of energy that is required to remove an electron from an atom in a gaseous formation.
- Ionization energy performs periodicity on the periodic table.
- In general, basic ionization energy trend is found that it decreases while moving from right to left across an element period. And the reason behind happening this is that, while moving from right to left atomic radius increases and electrons are loosely connected to the nucleus
- General trend for ionization energy is to get decreased while moving from top to bottom of a periodic table group. More moving down towards bottom; an extra valance electron shell is added to the atom and the distance of this particular shell from the nucleus is continually increased. So that it becomes easier to remove an electron from the valance shell.
- The basic unit of ionization energy is either kilo joules/mole (KJ/mol) or electron volts (eV)
Infringements of the ionization energy trend
If we look after the chart of all the ionization energies, two infringements of the ionization energy trend are easily discernible. For example, ionization energy of boron is lesser than beryllium and ionization energy of oxygen is lesser than nitrogen. And the reason behind this occurrence is the different electron configuration of these elements and also the Hund’s rule.
If we look at the atomic structure of the beryllium then we will see that the first ionization electron comes from the 2s orbital. But in the case of boron ionization depends on 2p electron.
Whereas nitrogen and oxygen both have their ionization potential electron in their 2p orbital but there is a set of paired electrons exists in the 2p orbital of the oxygen.
Electron Binding Energy
Did you guys ever heard about the term called electron binding energy? If not then listen to me carefully!
Electron binding energy is the gentile term for the ionization energy that can be a great substitute for some specific element with any kind of charge state. For example, electron binding energy of the chloride ion is the particular amount of energy that is needed to remove an electron for the chlorine ion when it holds the charge of -1. In this specific example electron binding energy will have the same magnitude as the magnitude of the electron affinity for the neutral chlorine atom. In other ways electron removal from decarboxylate dianion [–O2C(CH2)8CO2– ] requires the minimum amount of energy which is called as electron binding energy.
So here I have discussed the most important parts about ionization energy and its trends. I hope this guide will help you to build your concept on this topic.
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