Question

Which of the following statements is true about the variation of density of elements in the periodic table?

• A. In a period from left to right density first increases upto the middle and then starts decreasing.
• B. In a group on moving down the density decreases from top to bottom.
• C. A less closely packed solid has higher density.
• D. Density of elements is not a periodic property.

Answer 1

Answer: (A)

In a period from left to right density first increases upto the middle and then starts decreasing.
On moving from left to right in a period, one electron and one proton is added.
On moving from left to right in a periodic table, the atomic volume first decreases and then increases.
Initially, the increase in nuclear charge overcomes the increase in the number of electrons. Hence the atomic volume decreases.
But in the right of the periodic table newly added electrons goes into the p orbital. Due to high shielding power of s and p orbitals, atomic volume increases.
But atomic mass increases from left to right in a period.