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प्रश्न
The elements 4Be, 12Mg and 20Ca, each having two valence electrons in their valence shells, are in periods 2, 3 and 4 respectively of the modern periodic table. Answer the following questions associated with these elements, giving reason in each case:
(a) In which group should they be?
(b) Which one of them is least reactive?
(c) Which one of them has the largest atomic size?
उत्तर
(a) All three elements have valency 2. Thus, they should be present in group 2 of the periodic table.
(b) On going down a group in the periodic table, the reactivity of an element increases because of decrease in the effective nuclear charge and increase in the atomic size; this makes the removal of valence electrons easy. Thus, among the given elements, 4Be is the least reactive element.
(c) On going down a group in the periodic table, the atomic size of elements increases because of the addition of new shells. Thus, among the given elements, 20Ca has the largest atomic size.
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संबंधित प्रश्न
The atomic numbers of three elements A, B and C are 12, 18 and 20 respectively. State, giving reason, which two elements will show similar properties.
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.
Why are noble gases placed in a separate group?
Fill in the blank:
on moving from right to left in the second period, the number of valence electrons……….
Choose the word or phrase from the bracket which correctly complete each of the following statement:
Metals are good ................. (oxidising agents/reducing agents) because they are electron ............. (acceptors/donors).
The electronic configuration of an element is 2, 8, 4. State it:
name and write its one physical property.
Select the correct answer from the options given below.
It is a period having elements from atomic no. 11 to 18.
Give a reason for the following:
A transition from metallic to non-metallic elements is seen on moving from left to right in a period of the periodic table.
Which of the following would weigh the least?
(Atomic masses C = 12, 0 = 16, Na = 23)
There are three elements E, F, G with atomic numbers 19, 8 and 17 respectively.
Classify the above elements as metals and non-metals.
