Shielding and Effective Nuclear Charge

What is the trend for electronegativity as you move left to right across a period and why?

• EN increases because the shielding effect increases causing the effective nuclear charge to decrease as you add more protons to the nucleus

• EN decreases because the shielding effect decreases causing the effective nuclear charge to increase as you add more protons to the nucleus

• EN increases because the effective nuclear charge increases as you add protons to the nucleus and increase the number of valence electrons in the outer shell

• EN decreases because the effective nuclear charge decreases as you reduce the number of protons in the nucleus and increase the number of valence electrons in the outer shell

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What is the trend for EN as you move down a group or family and why?

• EN increases because the number of energy levels decrease causing an increase in the shielding effect and a decrease in the effective nuclear charge.

• EN decreases because the number of energy levels increases causing an increase in the shielding effect and a decrease in the effective nuclear charge

• EN increases because the number of energy levels increases causing a decrease in the shielding effect and an increase in the effective nuclear charge

• EN decreases because the number of energy levels decrease causing a decrease in the shielding effect and a decrease in the effective nuclear charge.

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Which element has the least effective nuclear charge?

• N

• F

• Li

• Be

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As you move down a group the effective nuclear charge ________ as the shielding effect _________

• decreases, increases

• decreases, decreases

• increases, increases

• increases, decreases

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What has the greatest effect on electronegativity as you move across a period? (check all that are correct)

• shielding effect

• effective nuclear charge

• number of neutrons

• number of protons

• number of energy levels

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The effective nuclear charge, Zeff, experienced by valence electrons in an atom can be estimated from the equation: Zeff = the number of protons – the number of core electrons

Using this estimation, effective nuclear charge for Main Group elements would _________ left to right across a period and _______ down a group. Which option correctly completes the blanks in the statement?

• increase; decrease

• increase; remain the same

• decrease; remain the same

• remain the same; remain the same

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The valence electrons of an atom do not experience the full attractive force of protons in the atom's nucleus due to the presence of inner core electrons. The reduction in nuclear charge experienced by valence electrons due to inner core electrons is called the

• ionization energy effect

• nuclear charge effect

• periodic law effect

• shielding effect

The concept of shielding happens because of

• attraction between nucleus and valence electrons

• attraction between nucleus and core electrons

• repulsion between valence electrons and other valence electrons

• repulsion between core electrons and valence electrons

What is the effect of increased shielding on the effective nuclear charge experienced by valence electrons?

• A) It increases the effective nuclear charge.

• B) It decreases the effective nuclear charge.

• C) It has no effect on the effective nuclear charge.

• D) It doubles the effective nuclear charge.

Which of the following elements is likely to have the highest effective nuclear charge?

• A) Sodium (Na)

• B) Magnesium (Mg)

• C) Aluminum (Al)

• D) Silicon (Si)

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