Which statement is true about effective nuclear charge? a. Effective nuclear charge decreases as we move to the right across a row in the periodic tableb. Effective nuclear increases as we move to the right across a row in the periodic tablec. Effective nuclear charge remains relatively constant as we move to the right across a row in the periodic tabled. effective nuclear charge increases and decreases at the regular intervals as we move to the right across in the row periodic table

Question

Caitlin Brown

Physics

20 April, 11:33

Which statement is true about effective nuclear charge? a. Effective nuclear charge decreases as we move to the right across a row in the periodic tableb. Effective nuclear increases as we move to the right across a row in the periodic tablec. Effective nuclear charge remains relatively constant as we move to the right across a row in the periodic tabled. effective nuclear charge increases and decreases at the regular intervals as we move to the right across in the row periodic table

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Curtis Mills · Answer 1

Option b. Effective nuclear charge increases as we move to the right across a row in the periodic table

Explanation:

The effective nuclear charge is a measure of how strong the protons in the nucleus of an atom attract the outermost electrons of such atom.

The effective nuclear charge is the net positive charge experienced by valence electrons and is calculated (as an approximation) by the equation: Zeff = Z - S, where Z is the atomic number and S is the number of shielding electrons.

The shielding electrons are those electrons in between the interesting electrons and the nucleus of the atom.

Since the shielding electrons are closer to the nucleus, they repel the outermost electrons and so cancel some of the attraction exerted by the positive charge of the nucleus, meaning that the outermost electrons feel less the efect of attraction of the protons. That is why in the equation of Zeff, the shielding electrons (S) subtract the total from the atomic number Z.

The effective nuclear charge, then, is responsible for some properties and trends in the periodic table. Here, you can see how this explains the trend of the atomic radius (size of the atom) accross a row in the periodic table.

As the effective nuclear charge is larger, in a same row of the periodic table, the shielding effect is lower, the outermost electrons are more strongly attracted by the nucleus, and the size of the atoms decrease. That is why as we move to the right in the periodic table, the size of the atoms decrease.