Question

An element with atomic number $17$ is placed in the group $17$ of the long form periodic table. Element with atomic number $9$ is placed above and with atomic number $35$ is placed below it. Element with atomic number $16$ is placed left and with atomic number $18$ is placed right to it. Which of the following statements are correct:
(i) Valency of the element with atomic number $18$ is $0$
(ii) Elements with same valency have atomic number $16,17$ and $18$
(iii) Valency of elements with atomic number $9,17$ and $35$ is one
(iv) Element with atomic number $17$ is more electronegative than elements with atomic number $16$ and $35$

• A. (i), (ii) and (iii)
• B. (i), (iii), and (iv)
• C. (i), (iii), and (iv)
• D. (i), (ii) and (iv)

Answer 1

The correct option is B (i), (iii), and (iv)

The element with the atomic number $18$ is argon. It is a noble gas and belongs to zero group or ${18}^{th}$ group. It has its octet complete and so the valency is zero. Elements with atomic number $9,17$ and $35$ are $F,Cl$ and $Br$. They are all halogens and belong to group $17$. All halogens have valency $1$. As the atomic size increases, electronegativity decreases. In a period moving left to right, electronegativity increases and in a group, on moving down, it decreases. Thus, $17$ is more electronegative than $16$ and $35$.
Hence, the correct option is b.