Question

(A) What is a period in a periodic table? How do atomic structures (electrons arrangements) change in a period with increase in atomic numbers from left to right?
(B) How do the following change on going from left to right in a periodic table?
(i) Chemical reactivity of elements
(ii) Nature of oxides of elements
Give examples in support of your answer.

Answer 1

Hint : There are a lot of elements present in this world, some exist independently, while some exist as an impurity, some as a mineral of two elements and of some we find only traces. All these elements were being discovered but didn’t have any order or a table to analyse them. That table of elements on this earth known to us of existence is called the periodic table.

Complete Step By Step Answer:
There are a lot of elements present in this world, some exist independently, while some exist as an impurity, some as a mineral of two elements and of some we find only traces. All these elements were being discovered but didn’t have any order or a table to analyse them. That table of elements on this earth known to us of existence is called periodic table.
This periodic table is further divided into periods and groups. There are 7 periods and 18 groups. Period is the horizontal row of the periodic table.
As we go along the group starting from the first period, we observe that the number of electrons increases. Therefore, from the left to write the number of electrons. Eg hydrogen has more electrons from helium, hydrogen has one and helium has two.
(I) the chemical reactivity of the elements from left to right increases but not for the last eighteenth group, because it has all filled electrons. As the number of electrons increases the number of unpaired electrons increases and so decreases the size of atoms and so increases the reactivity. Egg oxygen is always less electronegative than in fluorine as oxygen difluoride exists in which oxygen exists in a positive oxidation state.
(ii)more electropositive elements form basic oxides while more electronegative elements form acidic oxide, electro positivity is the readiness with the element leaves electron. So, we can say that basic nature decreases the oxides from left to right but acidic nature increases. Egg carbon dioxide is less acidic than oxygen difluoride.
(A) increases
(B)(I) increases, (iI)basic nature decreases and acidic nature increases.

Note :
Groups are divided in the periodic table on the basis of the number of electrons in the last shell. All the electrons down the group have the same electrons and the electron shells increase so increases the size of the atom.