Ionization Energy Trends, Shielding effect and Nuclear Charge.

Your Questions: What is the Ionization Energy Trend in Periodic Table? Why Ionization Energy decreases from top to bottom? Why across the period ionization energy increases? What is shielding effect? How shielding Effect works in periodic table? Is Ionization Energy depends upon Nuclear charge?

Ionization Energy Variation within Group:

The factors upon which the ionization energy of an atom mainly depends:

  1. Magnitude of nuclear charge.
  2. Size of atom.
  3. Shielding effect.

What is Shielding Effect?

The shielding effect is actually the repulsion due to electrons in between the nucleus and the outermost shell.

This effect increases as the size of atom increases due to addition of an extra shell  successively in each period hence more number of electrons shields the nucleus.

Trend in Group:

Going down in a group, the nuclear charge increases but as the size of atom and the number of electrons causing the shielding effect also increases therefore ionization energy decreases top to bottom.

That’s why in alkali metals, for example, it is easier to remove an electron from ceasium atom than from Lithium atom.

Ionization Energy Variation Across a Period:

Generally, smaller the atom with greater nuclear charge, more strongly the electrons are bound to the nucleus and hence higher the ionization energy of atom.

By moving from left to right in a period, the outer shell remains the same, while the nuclear charge increases effectively that makes the removal of an electron difficult and hence the value of ionization energy increase.

Although, the number of electrons also increases in this case but, the shielding is not very effective within the same shell.

Review the Topic:

Q: What is the Ionization Energy Trend in Periodic Table?

A: Explained above.

Q: Why Ionization Energy decreases from top to bottom?

A: Due to shielding and Nuclear Charge Effect. Read above paragraph carefully.

Q: Why across the period ionization energy increases?

A: Answered.

Q: What is shielding effect?

A: Check out its definition above.

Q: How shielding Effect works in periodic table?

A: Read the role of shielding effect in Group as well as in periodic table in above headings.

Q: Is Ionization Energy depends upon Nuclear charge?

A: Off-course, How? i mentioned above.

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Fawad's Chemistry

Hope you fine. I'm Fawad and author of this blog "Chemanalogy". Love to write on Chemistry. Currently teaching A Levels, O Levels and University Chemistry offline as well as online. Connect to chemanalogy community by subscribing via email.
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