# Ionization energy: types, factors, calculations, exceptions to trends (2023)

This is the energy required to remove one or more electrons from a neutral atom to produce a positively charged ion that changes the chemical behavior of the atom.

Ionization energy (IE) is necessary to remove one or more electrons from neutral valence to produce a positively charged ion and change the chemical properties of an atom.

It is often expressed in kJ/mol, and the measurement is based on a single gas atom. All elements in the periodic table have a characteristic known as ionization energy, sometimes called ionization potential.

i.e. can be represented as shown

• X + first ionization energy → X++ e-

Where

• X is a neutral atom.
• X+is an ion of atom X with a single positive charge.
• is an electron with a single negative charge.

Contents

## Types of ionization energy

### First ionization energy

The "first ionization energy" of an element refers to the energy required to remove the outermost valence electron from a neutral atom in the gas phase.

In the equation, it refers to I.E. required to remove the first electron from a neutral atom, yielding an ion with a single positive charge. The process by which the first I.E. the measured sodium content will be represented by the following equation:

(Video) Ionization Energy - Basic Introduction

Na (g) + energyAlready+(g) + e

### Second ionization energy

The second ionization energy needed to remove the next electron is always higher than the first ionization energy because it takes even more energy to remove an electron from a cation than from a neutral atom.

In the case of an alkali metal atom, since its loss gives the atom a stable electron shell, removal of the first electron is quite simple. The removal of the second electron creates a new electron shell that is tighter and more closely bound to the atomic nucleus.

The process by which the second I.E. the measured sodium content will be represented by the following equation:

Na (g) + energyAlready2+(g) + e

### Third ionization energy

The "third ionization energy" of an element refers to the energy required to remove the third electron. It has to be formed3+cations.

The process by which the third I.E. the measured sodium content will be represented by the following equation:

All elements have a first ionization energy, even atoms that do not form positive ions in test tubes.

Throughout the periodic table, the first ionization energy varies continuously. IE decreases from top to bottom in groups and increases from left to right in a period. Therefore, helium has the highest first ionization energy, while francium has one of the lowest.

## Factors affecting the amount of ionization energy

Ionization energy is a measure of the force needed to eject a particular electron from the gravitational pull of the nucleus. The high price of I.E. shows a strong attraction between the electron and the nucleus. The size of this attraction will be determined as follows:

(Video) Periodic Trends: Electronegativity, Ionization Energy, Atomic Radius - TUTOR HOTLINE

The distance of the electron from the nucleus:

The distance between the electrons and the nucleus affects the attraction. It decreases rapidly as space increases. An electron closer to the nucleus is attracted more strongly than an electron farther away.

Nuclear charge:

When the number of protons in a nucleus increases, its positive charge increases and vice versa. Electrons tend to be strongly attracted to positively charged nuclei.

The number of electrons between the outermost electrons and the nucleus:

Let's look at the sodium atoms with the electron structure 2,8,1.

There are two electron shells between the outer electron and the nucleus. The 11 protons in the sodium nucleus are reduced by the inner electrons. The outer electron only feels a net attraction of about 1+ from the center. This reduction in the strength of the nucleus by the inner electrons is known as shielding or shielding.

Penetration Electron effect
A single atom can contain various subshells, including the s, p, d, and f subshells. Unlike the p and other subshells, the s subshell is known to be closer to the nucleus. Unlike the other subcortex, the s subcortex has a stronger affinity for the nucleus, making it difficult to remove electrons from it. Therefore, additional ionization energy is required to remove electrons from the s subshell.

Fully and half-filled electrons

I.E is greater in fully filled orbitals than in partially filled or partially filled orbitals. Partially filled orbitals are less stable than fully filled orbitals.

## Calculation of ionization energy

The following equation can be used to calculate the ionization potential of hydrogen:

(Video) The Periodic Table: Atomic Radius, Ionization Energy, and Electronegativity

E =doc RH( 1/n2), Where

• Mis the energy of the electron (or the amount of energy needed to remove an electron, ionization energy)
• theis Planck's constant = 6.626 * 10-34Js (seconds)
• Dois the speed of light = 3.00 * 108m/s (meters/second)
• RHis the Rydberg constant = 1.097 * 107M-1(1/meter)
• Nis the principal quantum number (or energy level) of the electron

After applying constant values, the equation becomes:

E = (2,18 * 10-18J)(1/n2)

From here, you can enter a value for the electron's energy level to calculate how much power is needed to remove it.

## A unit of ionization energy

Ionization energy is usually expressed in kcal/mol, kJ/mol, or electron volts (eV) per atom. Mathematics,

A single electron volt (eV) is 3.827*10-20per person.

= 3827 x 10-20x 4.184 calories per person (∵cal=4.184 J)

= 1602 x 10-19J per person

= 1602 x 10-19x 6022 *1023J/mol

= 96472 J mol-1

= 96 472 kJ times-1

(Video) Exception to the Ionization Energy Trend

## Energy potential of ionizationPeriodic table

• Moving from left to right over the period of an element (series), the ionization energy tends to increase. The reason for this is that the radius of an atom decreases as we go through a period. This occurs when more protons are supplied, increasing the nucleus-electron attraction and pushing the electron shells closer together.
• The ionization energy generally decreases moving from top to bottom of a group of elements (column) as the principal quantum number of the outermost (valence) electron increases moving downwards. Atoms have more protons moving down the group which attract electron shells. The outer electrons are further away from the nucleus because each row adds a new shell.
• Helium, one of the noble gases, has the highest ionization energy and is found in the upper right corner of the periodic table. Fransium, the alkali metal on the left side of the map, has one of the lowest ionization energies.
• Typically, group 2 elements have a higher ionization energy than group 13 elements, and group 15 elements have a higher ionization energy than group 16 elements.
• Groups 2 and 15 have fully and half-filled electron configurations, respectively, so more energy is required to remove an electron from fully filled orbitals than from incompletely filled orbitals.
• The alkali metals (group IA) have low ionization energies, especially compared to halogens or group VIIA.

## Turn off the ionization energy trend in the periodic table

• Boron has a lower first I.E. instead of beryllium. By comparing their electron configuration, we can analyze differences in their ionization energies. Boron with outer electrons in the "s" orbital is very close to the nucleus, while beryllium releases its first electron from the p orbital, which is relatively far from the nucleus.
• Nitrogen has three p-orbital electrons while oxygen has four electrons. Nitrogen should have a lower IE, but instead has a lower first ionization energy than oxygen due to the symmetrical arrangement of the three electrons in the p orbital of the nitrogen atom, according to Hund's rule. Another reason for this exception is electron-electron repulsion.
• Lanthanides and actinides have lower ionization energies due to the presence of an inner "f" electron shell.

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• Periodic table of elements - definition, terms, 118 elements
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## 1st, 2nd and 3rd ionization energies

• I1 = first ionization energy (energy needed to remove an electron from a neutral atom)
• I2is the second ionization energy (the energy needed to remove an electron from an atom with a +1 charge).

Each subsequent ionization energy is greater than the previous one.

That impliesI123<...N will always be true.

Here is an example showing how the ionization energy increases as electrons are ejected sequentially.

Mg (g) → Mg+(g) + eI1= 738 kJ/mol

Mg+(g) → Mg2+(g) + eI2= 1451 kJ/mol

See the first, second and third ionization energies of elements/ions

## bibliographic references

• F. Albert Cotton i Geoffrey Wilkinson, Advanced Inorganic Chemistry (wyd. 5, John Wiley 1988) s. 1381.
• Lang, Peter F.; Smith, Barry C. "Ionization energies of atoms and atomic ions." Journal of Chemical Education. 80 (8).
• Cotton, F. Albert; Wilkinson, Geoffrey (1988). Advanced Inorganic Chemistry (5η έκδ.). John Wiley. ISBN0-471-84997-9.
• Housecroft, CE; Sharpe, AG (1 listopada 1993).Inorganic Chemistry(eBook). Inorganic Chemistry. Volume 3 (15th). Switzerland: Pearson Prentice-Hall. pp. 536, 649, 743.
• https://brilliant.org/wiki/ionization-energy/
• https://chemistrytalk.org/ionization-energy-trend/

## FAQs

### What are the exceptions to the trend in ionization energy? ›

Since going from right to left on the periodic table, the atomic radius increases, and the ionization energy increases from left to right in the periods and up the groups. Exceptions to this trend is observed for alkaline earth metals (group 2) and nitrogen group elements (group 15).

What factors determine ionization energy? ›

Ionization energy depends on two factors:
• The force of attraction between electrons and the nucleus.
• The force of repulsion between electrons.
Aug 22, 2019

What were the four main factors that affected the amount of ionization energy? ›

The factors that influence the ionisation energies are :
• the size of the atom.
• the charge on the nucleus.
• how effectively the inner electron shell screen the nuclear charge.

What are the exceptions for ionization energy in period 3? ›

However, the trend has two anomalies. The first is between Mg and Al, because the outer electron of Mg is in the orbital 3s, whereas that of Al is in 3p. The 3p electron has more energy than the 3s electron, so the ionization energy of Al is actually less than that of Mg.

What is one of the exceptions to the trends in the periodic table? ›

Group 8A atoms are an exception to the periodic trend rule. Group 8A atoms belongs to zero group elements or inert gases or Noble gases. These elements generally do not participate in chemical reactions.

What is the trend in ionization energy? ›

What is the trend for ionization energy? The general trend of ionization energy in a periodic table is that the energy increases as you move in the direction of hydrogen to helium and decreases as you move from hydrogen to cesium.

Which one of the following will not affect ionization energy? ›

Shielding effect does not have any effect on I.P.

What are the three factors that determine the magnitude in the first ionization energy? ›

For example,O(g)→ O+(g)+ e-The three factors that affect ionisation energy are the size of the positive nuclear charge, the size of the atom i.e. distance of outermost electron from the nucleus and screening (shielding) effect of inner shell electrons.

What are the 3 factors that affect atom size ionization energy and electronegativity? ›

There are three factors that help in the prediction of the trends in the Periodic Table: number of protons in the nucleus, number of shells, and shielding effect.

What are the exceptions to the atomic radius trend? ›

Periodic Trend

The atomic radius of atoms generally decreases from left to right across a period. There are some small exceptions, such as the oxygen radius being slightly greater than the nitrogen radius. Within a period, protons are added to the nucleus as electrons are being added to the same principal energy level.

### What are the exceptions to electron configuration? ›

There are two main exceptions to electron configuration: chromium and copper. In these cases, a completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.

What are the 3 factors that impact periodic trends? ›

There are three factors that help in the prediction of the trends in the periodic table: number of protons in the nucleus, number of energy levels, and the shielding effect. The atomic radii increase from top to the bottom in any group. The atomic radii decrease from left to right across a period.

What are 4 important periodic trends? ›

Periodic trends are patterns in elements on the periodic table. Major trends are electronegativity, ionization energy, electron affinity, atomic radius, and metallic character.

What are the exceptions to the first 20 elements? ›

Exceptions are nitrogen, argon and chlorine.

What are the trends in ionization energy quizlet? ›

Ionization energy tends to increase across a period because electrons are added to the same main energy level Ionization energy tends to increase across a period because the nuclear charge increases.

What is the trend of ionization energy and reactivity? ›

On-going left to right in a period, the ionization energy increases and reactivity decreases. On-going down in a group, the electrons get added in the next higher shell, so the attraction of the nucleus on the outermost shell decreases so, the size of the atom increases.

What is the formula for ionization energy? ›

Numerically, we describe ionization energy as the orbital energy of the electron with the reverse sign. The ionization energy = + 2.18 × 10–18 J/atom (or + 1312.3 KJ/mole).

Which factor does not affect the extent of ionization? ›

Current does not effect the degree of ionization.

On which factors and ionization energy does not depend? ›

Answer: The ionization energy of an element does not depends on electron neutrality.

What does ionization energy depend on quizlet? ›

ionization energy depends on the effective nuclear charge and the shielding effect, which in turn depend on the atomic radius.

### How to determine which element has the highest ionization energy? ›

The first ionization energy varies in a predictable way across the periodic table. The ionization energy decreases from top to bottom in groups, and increases from left to right across a period. Thus, helium has the largest first ionization energy, while francium has one of the lowest.

What makes first ionization energy higher? ›

On the periodic table, first ionization energy generally increases as you move left to right across a period. This is due to increasing nuclear charge, which results in the outermost electron being more strongly bound to the nucleus.

What are three factors which influence the size of an atom or ion? ›

These factors are: The number of protons in the nucleus (called the nuclear charge). The number of energy levels holding electrons (and the number of electrons in the outer energy level). The number of electrons held between the nucleus and its outermost electrons (called the shielding effect).

What are the various factors due to which the ionization energy of the main group elements tends to decrease down a group? ›

Ionization enthalpy of the main group elements tends to decrease down the group due to the following factors such as atomic size, shielding or screening effect and nuclear charge.

What are the two factors that affect the trends for the electronegativity? ›

An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus.

What are the exceptions to electron affinity and ionization energy? ›

Exceptions to electron affinity trends include the noble gases, fluorine and Groups 2, 14 and 15 in the periodic table.

Are there any exceptions to the trend in electronegativity? ›

From top to bottom down a group, electronegativity decreases. This is because atomic number increases down a group, and thus there is an increased distance between the valence electrons and nucleus, or a greater atomic radius. Important exceptions of the above rules include the noble gases, lanthanides, and actinides.

Why is oxygen an exception to the ionization energy trend? ›

The last electron in the oxygen atom is forced into an already occupied orbital where it is kept close to another electron. The repulsion between these two electrons makes one of them easier to remove, and so the ionization energy of oxygen is lower than might be expected.

Are there any exceptions to the atomic radius trend? ›

The atomic radius of atoms generally decreases from left to right across a period. There are some small exceptions, such as the bismuth (Bi) radius being slightly greater than the polonium (Po) radius.

What are the exceptions to electron? ›

There are two main exceptions to electron configuration: chromium and copper. In these cases, a completely full or half full d sub-level is more stable than a partially filled d sub-level, so an electron from the 4s orbital is excited and rises to a 3d orbital.

### Which of the following groups is an exception to the electron affinity trend? ›

The major exception to this rule is the noble gases. Noble gases follow the general trend for ionization energies, but do not follow the general trend for electron affinities.

What is the trend of ionization energy? ›

What is the trend for ionization energy? The general trend of ionization energy in a periodic table is that the energy increases as you move in the direction of hydrogen to helium and decreases as you move from hydrogen to cesium.

What are the exceptions in the periodic table? ›

Exceptions to the States of the Periodic Table
• Mercury. The shiny metal Mercury at room temperature unlike all metals in the periodic table exists as a liquid. ...
• Bromine. Again another liquid in the periodic table, located in Group 7 Bromine is the only other known liquid in the periodic table. ...
• Carbon.

What elements do not have an electronegativity value and why? ›

Since electronegativity measures the amount of attraction between an atom and an electron, noble gases do not have electronegativity.

Why is nitrogen an exception to ionization energy? ›

Nitrogen has three unpaired electrons, while oxygen only has two. Oxygen is the first element to "pair" its electrons. This pairing of electron creates more electron-electron repulsions, and thus, the ionization energy of oxygen is lower than nitrogen, which doesn't have any paired electrons in the p orbital.

What is the trend for electron affinity? ›

Electron affinity increases upward for the groups and from left to right across periods of a periodic table because the electrons added to energy levels become closer to the nucleus, thus a stronger attraction between the nucleus and its electrons.

Which requires more ionization energy? ›

Hydrogen's ionization energy is very high (at 13.59844 eV), compared to the alkali metals.

What 4 types can the atomic radius be specified? ›

What influences the trend of atomic radius? ›

A higher effective nuclear charge causes greater attractions to the electrons, pulling the electron cloud closer to the nucleus which results in a smaller atomic radius. Down a group, the number of energy levels (n) increases, so there is a greater distance between the nucleus and the outermost orbital.

What are the exceptions to the transition metal rule? ›

Many of the transition metals (orange) can have more than one charge. The notable exceptions are zinc (always +2), silver (always +1) and cadmium (always +2).

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