Periodic Trends

What happens to the atomic radius as you move across a period from left to right?

• It increases.

• It decreases.

• It fluctuates randomly.

• It remains the same.

Why does the atomic radius decrease across a period?

• Because the electrons move to higher energy levels.

• Because the number of electron shells increases.

• Because the nuclear charge decreases.

• Because the nuclear charge increases, pulling electrons closer.

What happens to the atomic radius as you move down a group?

• It decreases.

• It remains the same.

• It fluctuates randomly.

• It increases.

Why does the atomic radius increase down a group?

• Because each new row adds another (principal) energy level.

• Because the electrons are pulled closer to the nucleus.

• Because the number of protons decreases.

• Because the nuclear charge decreases.

What is the trend for electronegativity across a period?

• It fluctuates randomly.

• It remains the same.

• It increases.

• It decreases.

Why does electronegativity increase across a period?

• Because the electrons are further from the nucleus.

• Because the nuclear charge decreases.

• Because the nuclear charge increases, attracting bonding electrons more strongly.

• Because the number of electron shells increases.

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What is the trend for electronegativity down a group?

• It decreases.

• It increases.

• It fluctuates randomly.

• It remains the same.

Why does electronegativity decrease down a group?

• Because the number of protons decreases.

• Because the nuclear charge increases.

• Because the valence electrons are in higher energy levels and further from the nucleus.

• Because the valence electrons are closer to the nucleus.

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What is the trend for first ionization energy across a period?

• It fluctuates randomly.

• It remains the same.

• It decreases.

• It increases.

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Why does first ionization energy increase across a period?

• Because the number of electron shells increases.

• Because the nuclear charge decreases.

• Because the electrons are held more tightly due to increased nuclear charge.

• Because the electrons are in higher energy levels.

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NGSS.HS-PS1-1

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