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प्रश्न
Write the number of periods the Modern Periodic Table has. State the changes in valency and metallic character of elements as we move from left to right in a period. Also state the changes, if any, in the valency and atomic size of elements as we move down a group.
उत्तर
The modern periodic table has seven periods.
On moving from left to right in the periodic table, the metallic character of elements decreases, while the valency first increases from 1 to 4 and then decreases to 0 (zero).
On moving down the group, the atomic size of the elements increases, but the valency remains the same.
संबंधित प्रश्न
Given below are some elements of the modern periodic table. Atomic number of the element is given in parentheses.
A(4), B(9), C(14), D(19), E(20)
(a) Select the element that has one electron in the outermost shell. Also, write the electronic configuration of this element.
(b) Which two elements amongst these belong to the same group? Give reasons for your answer.
(c) Which two elements amongst these belong to the same period? Which one of the two has bigger atomic radius?
The elements Be, Mg and Ca each having two electrons in their outermost shells are in periods 2, 3, and 4 respectively of the modern periodic table. Answer the following questions, giving justification in each case:-
(i) Write the group to which these elements belong.
(ii) Name the least reactive element.
(iii) Name the element having largest atomic radius.
Write the number of vertical columns in the modern periodic table. What are these columns called?
Match the atomic number 2, 4, 8, 15 and 19 with each of the following
1) A solid non metal belonging to the third period.
2) A metal of valency 1.
3) A gaseous element with valency 2.
4) An element belonging to Group 2
5) A rare gas.
Explain why, the properties of elements are repeated after 2, 8, 18 and 32 elements in the periodic table.
Name two properties of elements whose magnitudes change when going from top to bottom in a group of the periodic table. In what manner do they change?
On the basis of electronic configuration, how will you identify the first and the last element of a period?
The elements of one short period of the periodic table are given below in order from left to right:
Li Be B C O F Ne
(a) To which period do these elements belong?
(b) One element of this period is missing. Which is the missing element and where should it be placed?
(c) Place the three elements, fluorine, beryllium and nitrogen, in the order of increasing electro negativity.
(d) Which one of the above elements belongs to the halogen series?
State the property trends in general of elements on moving down in a group of the periodic table.
State the following:
The group which contains highly electropositive metals including sodium.
