Ionization energy, also known as ionization potential, is the amount of energy required to remove an electron from an atom or ion. It is a measure of the strength of the attractive force between the nucleus and the electrons in an atom or ion. In this article, we will study in detail what ionization energy is and how to find ionization energy.
Ionization Energy- Definition
The electrons in an atom are attracted by the nucleus as it is positively charged. To remove an electron from an atom, energy has to be supplied. The quantitative measure of the tendency of an atom to lose an electron is given by ionization energy/enthalpy. It can be defined as: The energy that is needed to remove the most loosely attached electrons from an isolated gaseous atom of the element in its ground state. It is also known as ionization potential because it is the minimum potential difference that is needed to remove the most loosely bound electrons from a gaseous atom to form a gaseous cation. The ionization energy/enthalpy is expressed in units of KJ mol–1 or electron volt (eV0 per atom or k cal mol–1.
1. Factors Affecting Ionization Energy
The following factors affect ionization enthalpy:
Nuclear charge: The ionization enthalpy increases as the atomic number of the element increases. This is because the electrons are held more tightly by the positive nucleus.
Electron shielding: Electron shielding refers to the electrons in the inner shells that partially shield the outer electrons from the positive nucleus. If the shielding is greater, the ionization enthalpy will be lower.
Electron configuration: The ionization enthalpy is higher for atoms with completely filled electron shells because it is a little more difficult to remove an electron from such atoms.
The size of the atom also affects its ionization enthalpy. As the size of the atom increases, the ionization enthalpy decreases. This is because the electrons in larger atoms are farther from the nucleus and thus experience weaker attraction.
Electron affinity: Electron affinity refers to the energy change that occurs when an electron is added to a neutral atom. The ionization enthalpy of an atom is directly related to its electron affinity. If the electron affinity is high, the ionization enthalpy will also be high.
2. Determination
Of Ionization Energy Determining ionization energy requires a detailed understanding of quantum mechanics and the interactions between the nucleus and electrons in an atom or ion. In most cases, ionization energy is calculated using advanced computational methods such as quantum chemical calculations or density functional theory. However, for simple qualitative analysis and comparison, you can use the following general trends to estimate the ionization energy of an element:
As you move from left to right across a period (row) in the periodic table, the ionization energy generally increases. This is because the size of the atom decreases and the effective nuclear charge (the attractive force between the nucleus and the electrons) increases as you move from left to right.
As you move down a group (column) in the periodic table, the ionization energy generally decreases. This is because the size of the atom increases and the effective nuclear charge decreases as you move down a group.
The ionization energy of an element can also be influenced by its electron configuration and the shielding effect of inner electrons. Elements with a partially filled outer electron shell generally have lower ionization energy than those with a completely filled outer electron shell. [caption id="attachment_436" align="aligncenter" width="786"]
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3. Calculation of Ionization Potential
Method 1 Ionization potential can be calculated using the following equation:
Where
E = Ionization energy
h = Planck’s constant = 6.626 × 10-34 Js
c is the speed of light = 3.00 × 108 m/s
RH is Rydberg constant = 1.097 × 107 m-1
n is the principal quantum number (or energy level) of the electron After you insert the constant values, the equation becomes:
After you insert the constant values, the equation becomes:
To calculate the Ionization energy in KH/mol the equation will become:
You can then insert in the value of the electron's energy level to calculate the amount of energy required to remove it.
Sample Calculation Calculate the first Ionization energy of Hydrogen in its ground state. Solution: Using the equation:
where n1 = 1 because it is in the ground state. E = 1312 KJ/mol
Method 2 Ionization Energy can also be calculated in eV by the following equation:
Sample Calculation: Calculate the Ionization energy of the Lithium atom Solution: The electronic configuration for the lithium atom is 1s2 2s1. Therefore, Z (atomic number) = 3 and n = 2 as the electron will be removed from the 2nd level. On putting the values in the equation:
I.E = 30.6eV
Key Takeaways
Ionization energy can also be referred to as ionization potential.
The amount of energy that is needed to remove an electron from a neutral atom, resulting in the formation of an ion, is ionization energy.
Ionization energy is typically measured in kJ/mol and is based on an isolated atom in its gaseous phase.
Ionization energies increase over time.
Ionization energies decrease as one moves down a group.
FAQs
1. What is ionization energy?
Ionization energy can be defined as the energy needed to remove an electron that is loosely bound to the nucleus from a neutral atom to form a positive ion.
2. How is ionization energy measured?
Ionization energy is usually measured in units of electron volts (eV) or kilojoules per mole (kJ/mol).
3. How does ionization energy vary across the periodic table?
Ionization energy generally increases from left to right across a period and decreases from top to bottom down a group in the periodic table. This trend can be explained by the increasing nuclear charge and decreasing electron shielding.
4. How does the electron configuration of an atom affect its ionization energy?
Atoms with completely filled electron shells have higher ionization energy than atoms with partially filled electron shells. This is because removing an electron from an atom with a full electron shell is more difficult.
5. What is the distinction between ionization energy and electron affinity?
The energy required to remove an electron from a neutral atom is referred to as ionization energy, whereas electron affinity is the energy change that occurs when an electron is added to a neutral atom.
6. Can ionization energy be used to identify elements?
Yes, ionization energy can be used to identify elements, as it is a characteristic property of an element and varies in a predictable manner across the periodic table.
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