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Ionization Energy on the Periodic Table

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Periodic Trends

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Ionization Energy on the Periodic Table


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You will explore the Periodic Table through ionization energies, and gain an understanding of the technology behind neon lighting.

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Now You Know

After completing this tutorial, you will be able to complete the following:

  • Describe ionization energy as the energy needed to remove an electron from an atom in its gaseous state.
  • Describe the ionization energy trend as generally increasing across a period.
  • Describe the ionization energy trend as decreasing down a group in the Periodic Table.
  • Explain that ionization energy generally increases across a period because the greater number of protons results in greater positive charges that attract valence electrons more strongly.
  • Explain that ionization energy decreases down a group because valence electrons are further from the nucleus and thus more weakly attracted.

Everything You'll Have Covered

The energy needed to remove an electron from an atom is very important in determining the type of bond an atom creates with another atom. Ionization energy is defined as the energy needed to remove an electron from an atom in its gaseous state. An atom in its gaseous state means that it is not attached to other atoms in a solid or liquid state. When an atom loses an electron through ionization, it becomes an ion that has a net positive charge.

Ionization energy is low when the outermost electron is easily removed and little energy is needed. Conversely, ionization energy is high when more energy is needed to remove the outermost electron. Generally speaking, there is a trend for ionization energy to increase across the periods in the Periodic Table, and decrease down the groups. However, exceptions to the ionization energy trends across periods occur because of the subshells in the atom. The s and p orbitals have different shapes, and it is easier to remove the electrons from p orbitals. In addition, within a subshell, paired electrons are easier to remove than unpaired electrons because they repel each other.

Tutorial Details

Approximate Time 20 Minutes
Pre-requisite Concepts Learners should be familiar with atomic orbitals, atomic radius, electron configuration, Periodic Table, and photons.
Course Chemistry
Type of Tutorial Concept Development
Key Vocabulary ionization energy, periodic trends,