Question
Write the name of the atom having the smallest size.
✓
Answer
• The calculated value of atomic radius of hydrogen is 53 pm while the calculated value of atomic radius of helium is 31 pm .
• That is because we expect the atomic radius to decrease when we move across the period from left to the right.
• However, hydrogen is diatomic gas while helium is monoatomic gas.
• So, it is not appropriate to compare calculated values of atomic radii. Comparing van der Waals radii of both atoms would be more appropriate.
• The van der Waals radius of hydrogen atom is 120 pm while the van der Waals radius of helium atom is 140 pm .
• In this case, hydrogen is the smallest atom in the modern periodic table.
• That is because we expect the atomic radius to decrease when we move across the period from left to the right.
• However, hydrogen is diatomic gas while helium is monoatomic gas.
• So, it is not appropriate to compare calculated values of atomic radii. Comparing van der Waals radii of both atoms would be more appropriate.
• The van der Waals radius of hydrogen atom is 120 pm while the van der Waals radius of helium atom is 140 pm .
• In this case, hydrogen is the smallest atom in the modern periodic table.
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