Across a period from left to right, the atomic radius of the elements generally
Correct answer: A. decreases, because nuclear charge increases while electrons enter the same shell
- A. decreases, because nuclear charge increases while electrons enter the same shell
- B. increases, because more electrons are added
- C. stays the same
- D. increases, because the nuclear charge decreases
Explanation
Each successive element adds one proton and one electron, but the electron enters the same outermost shell, so shielding hardly changes while the effective nuclear charge rises and the shell is pulled inwards. Down a group the opposite happens, since a whole new shell is added and radius increases. Atomic radius is the single trend from which ionisation energy and electronegativity mostly follow.
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About Periodic Properties and Trends
Periodic properties arise from electron configuration and effective nuclear charge, producing trends in atomic and ionic radius, ionization energy, electron affinity, electronegativity, metallic character and reactivity. Comparisons run across periods and down groups, with attention to common exceptions. The topic also relates these trends to the behavior of s-block and p-block elements.
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