Which statement about trends across a period is true?

Which statement about trends across a period is true?

• A. It increases
• B. It decreases
• C. It stays the same
• D. It varies randomly

Answer: (B)

Across a period, atomic size gets smaller because the nucleus gains more protons while electrons are added to the same energy level. The shielding effect from inner electrons stays about the same, so the increased positive charge pulls the outer electrons in more tightly. That stronger attraction shrinks the atomic radius from left to right. So the statement that describes the trend is that it decreases. The alternatives would imply growth, no change, or random variation, which doesn’t fit this consistent left-to-right tightening of the atom.

Across a period, atomic size gets smaller because the nucleus gains more protons while electrons are added to the same energy level. The shielding effect from inner electrons stays about the same, so the increased positive charge pulls the outer electrons in more tightly. That stronger attraction shrinks the atomic radius from left to right. So the statement that describes the trend is that it decreases. The alternatives would imply growth, no change, or random variation, which doesn’t fit this consistent left-to-right tightening of the atom.