Question

An element with atomic number $17$ is placed in the group $17$ of the long from 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?

a) Valency of the element with atomic number $18$ is zero.

b) Elements with same valency will have atomic number $16$, $17$ and $18$.

c) Valency of element with atomic number $9$, $17$ and $35$ is one.

d) Element with atomic number $17$ is more electronegative than element with atomic number $16$ and $35$.

• A. (a), (b) and (c)
• B. (a), (c) and (d)
• C. (b), (c) and (d)
• D. (a), (b) and (d)

Answer 1

The correct option is B (a), (c) and (d)

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