In going across a row of the periodic table, electrons are...

Name: Problem 12, Chapter 7: Chemistry
Uploaded: 2020-05-19T21:08:26-08:00
Duration: 3 min 45 s
Channel: Josiah Piceno
Description: In going across a row of the periodic table, electrons are added and ionization energy generally increases. In going down a column of the periodic table, electrons are also being added but ionization energy decreases. Explain.

In going across a row of the periodic table, electrons are added and ionization energy generally increases. In going down a column of the periodic table, electrons are also being added but ionization energy decreases. Explain.

Key Concepts

Atomic Radius

Atomic radius refers to the size of an atom, which is determined by the distance between the nucleus and the outermost electrons. This concept helps explain periodic trends: across a period, the increasing effective nuclear charge typically results in a smaller atomic radius, while down a group, the increasing number of electron shells leads to a larger atomic radius and more diffuse outer electrons.

Shielding Effect

The shielding effect describes how inner electrons reduce the full attractive force of the positively charged nucleus on the outer electrons. This effect becomes more pronounced down a group as additional electron shells are added, causing the outer electrons to feel a decreased effective nuclear charge and contribute to a lower ionization energy.

Effective Nuclear Charge

Effective nuclear charge is the net positive charge experienced by electrons after accounting for the repulsion effects of inner electrons. As one moves across a period, the effective nuclear charge increases because additional protons are added to the nucleus while the shielding effect from inner electrons remains relatively constant, leading to a stronger hold on the valence electrons.

Ionization Energy

Ionization energy is the amount of energy required to remove an electron from an isolated gaseous atom or ion. It is an important property because it reflects the strength of the attraction between the nucleus and the electrons. In the context of periodic trends, variations in ionization energy reveal how electron binding changes with atomic structure.

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