Question

Read the given expression. Effective nuclear charge = atomic number − X Which of the following explains the identity of X and its trends across a period?

Answer 1

Explanation:

X- are the non-valence or shielding electrons in an atom. They are the electrons in an atom which excludes the inner orbital ones.

The valence electrons are the electrons in the outermost shell of an atom.

  Effective nuclear charge = Atomic number - Non-valence electrons.

• The non-valence electrons are located inside of the main/inner electronic shell.  
• The valence electrons are located outside the main shell.

For example, Neon:

  Atomic number = 10

  Electronic configuration   1s² 2s² 2p⁶

       Non-valence electrons =  1s² = 2 electrons

       Valence electrons = 2s² 2p⁶ = 8 electrons

The trend of the non-valence electrons across the periodic table:

Down a group, new electronic shells are added, this implies that the non-valence electrons increases down the group.

Across the period, the number of the non-valence electrons stays the same because no additional electronic shells are added.

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Effective nuclear charge brainly.com/question/5441986

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