Question

Explain why are the following statements not correct.
(1) All groups contain metals and non metals
(ii) Atoms of elements in the same group have the
same number of electron(s).
iii) Non-metallic character decreases across a period
with increase in atomic number.
v) Reactivity increases with atomic number in a group
as well as in a period.​

Answer 1

Answer:

(i) Many groups like group 2,3 etc contain only metals. So the statement is false.

(ii) As we go down the group new shells are being added up or as we go down the group atomic number increases which causes increase in number of electron. So atoms of elements do not have same number of electron.

(iii) Non-metallic character relates to the tendency to accept electrons during chemical reactions. As we go from left to right  in a period the size of atom decreases thereby increasing the effective nuclear charge . Due to increase in effective nuclear charge the non metallic character increases from left to right in a period.

(iv) Reactivity refers to the tendency of the element to accept or donate electron.  Reactivity of halogen compound decreases down the group since as we go down the group the atomic size of the elements increases which decreases the effective nuclear charge thereby decreasing the tendency of element to gain electrons. Reactivity decreases as you go from left to right across a period. The farther to the left of  the periodic chart you go, the easier it is for electrons to be given away , resulting in higher reactivity.

Hope this answer helps you.