Answer the following questions:
(i) Name first element of period 7
(ii) As we move down the group, the atomic size increases or decreases?
(iii) What is common feature of electronic configuration in group 17.
(iv) Properties of eka silicon resembles with which element ?
(v) Be shows diagonal relationship with which element ?
(vi) Valency of group 18 elements.
Answers
Answering questions based on Periodic Table and its properties :
i) The first element of period 7 is the radioactive alkali metal, Francium. It is represented by the symbol Fr, and has an atomic weight of 87.
ii) As we move down a group, the atomic size increases. This trend is attributed to the following reasons :
• On moving down a group, the atomic number of the elements increases.
• Therefore, the number of electrons also increases equally.
• To accomodate these electrons, an extra shell gets added in every successive period.
• Due to this increase in the number of shells, the atomic size increases as we move down a group.
iii) The common feature of the electronic configuration of group 17 elements is that they all have a configuration of ns²np⁵ in their valence shell.
• This is because they all have 7 electrons in their valence shell, hence placed in group 17.
iv) Eka-silicon resembles metalloids in properties, namely, boron, silicon, arsenic, antimony and tellurium.
• Eka-silicon is actually germanium.
• Germanium is a metalloid, means, it has properties of both metals and non-metals.
• Hence, it resembles the elements which, too, are metalloid in nature.
v) Beryllium (Be) shows diagonal relationship with Aluminum (Al).
• Diagonal relationship means resemblance in properties of an element of period 2 with an element of period 3, placed below it diagonally.
• Be is placed in group 2 and period 2 of the periodic table. Al is placed in group 3, and period 3 of the periodic table, i.e., diagonally below Be.
vi) The valency of group 18 elements is zero.
• Group 18 elements are all noble gases.
• Noble gases have a complete octet.
• There is no extra electron in their valence shell. Hence, their valency is zero.