Question

An element with atomic number $17$ is placed in group $17$ of the long form of the periodic table. Element with atomic number $9$ is placed above and an atomic number $35$ is placed below it. Element with atomic number $16$ is placed left and an 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 the same valency will have atomic number $16,{\text{ }}17{\text{ and }}18$.
c) Valency of elements with atomic number $9,{\text{ }}17{\text{ and 35}}$ is one.
d) Element with atomic number $17$ is more electronegative than element with atomic number $16{\text{ and 35}}$.
A: (a), (b) and (c)
B: (a), (c) and (d)
C: (b), (c) and (d)
D: (a), (b) and (d)

Answer 1

Periodic table is the tabular representation of the elements. Elements are arranged according to increasing atomic numbers in this table. Down the group number of shells in which electrons are filled increases.

Complete step by step answer:
In this question we have given the atomic number of elements and their position in the periodic table. As we go down the group all the elements have the same electronic configuration and they belong to the same family. As we go down the group number of shells increases. When we go along the period all the elements have the same number of shells and their atomic number increases. Electronegativity is defined as the ability of an atom to pull a shared pair of electrons. As the size of the atom increases, the hold of nucleus on electrons decreases and electronegativity decreases. Down the group atomic size increases and hence electronegativity decreases. But along the period electronegativity increases because all the atoms tend to gain electrons and move toward stability. Atomic number of chlorine is $17$, fluorine is $9$ and bromine is $35$. All these elements belong to the halogen family and these elements are placed in group $17$. These elements have seven electrons in their outermost shell. These elements tend to gain one electron to gain stability (noble gas configuration). So, the valency of these elements is one.
Argon has atomic number $18$. This is a noble gas and hence this gas doesn’t react. So, the valency of this element is zero.
Atomic number of sulphur is $16$. This element is placed to the left of chlorine. As explained above electronegativity increases along the period, electronegativity of chlorine will be more than that of sulphur. Bromins is placed below chlorine therefore electronegativity of chlorine is more than that of bromine as well (as explained above). This means electronegativity of chlorine is more than that of sulfur and bromine.
From all these results we can conclude that statement (a), (c) and (d) are correct. Where statement (a) states that valency of the element with atomic number $18$ is zero, statement (c) states that valency of element with atomic number $9,{\text{ }}17{\text{ and 35}}$ is one and statement (d) states that element with atomic number $17$ is more electronegative than element with atomic number $16{\text{ and 35}}$. S

So, the correct answer is option B .

Note:
Down the group number of shells of the atom increases as a result size of the atom also increases. As the size increases hold of nucleus on the outermost shell electron decreases and it becomes easy to remove outermost shell electron