Understanding Electron Shielding and Effective Nuclear Charge

How many valence electrons does potassium have?

• 18

• 8

• 2

• 1

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What is the primary function of shielding electrons?

• To increase the ionization energy of valence electrons

• To shield valence electrons from the nucleus's full attraction

• To participate directly in chemical reactions

• To decrease the atomic radius of an atom

What remains constant across a period in terms of electron shielding?

• The number of shielding electrons

• The number of valence electrons

• The atomic radius

• The effective nuclear charge

Does electron shielding remain constant or change across a period?

• Increases

• Remains constant

• Varies unpredictably

• Decreases

Which element has the greatest amount of electron shielding in Group 1?

• Potassium

• Rubidium

• Sodium

• Lithium

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NGSS.HS-PS1-1

How is effective nuclear charge calculated?

• Protons minus neutrons

• Protons minus valence electrons

• Protons minus shielding electrons

• Neutrons minus shielding electrons

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What trend does effective nuclear charge show across a period?

• Remains constant

• Decreases

• Increases

• First increases, then decreases

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NGSS.HS-PS1-1

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Why does ionization energy increase across a period?

• Due to increased effective nuclear charge

• Because of increased electron affinity

• Due to increased atomic radius

• Because of decreased shielding

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NGSS.HS-PS1-1

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Does effective nuclear charge change down a group?

• Yes, it increases

• It remains the same

• It varies unpredictably

• Yes, it decreases

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NGSS.HS-PS1-1

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What causes the ionization energy to decrease down a group?

• Increase in atomic radius

• Decrease in shielding effect

• Increase in valence electrons

• Decrease in effective nuclear charge

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NGSS.HS-PS1-1

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