MCQ
Which of the following element has smallest size?
- A$K$
- ✓$Sr$
- C$Rb$
- D$Ba$
✓
Answer
Correct option: B.
$Sr$
b
As you go across a period, electrons are added to the same energy level. At the same time, protons are being added to the nucleus. The concentration of more protons in the nucleus creates a higher effective nuclear charge, In other words, there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius. So, all these elements belong to the $4^{th}$ group and $K r$ has the smallest atomic radii as it lies across the period.
As you go across a period, electrons are added to the same energy level. At the same time, protons are being added to the nucleus. The concentration of more protons in the nucleus creates a higher effective nuclear charge, In other words, there is a stronger force of attraction pulling the electrons closer to the nucleus resulting in a smaller atomic radius. So, all these elements belong to the $4^{th}$ group and $K r$ has the smallest atomic radii as it lies across the period.
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