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प्रश्न
How many groups and periods are there in the modern periodic table?
उत्तर
Modern periodic table consists of eighteen groups and seven periods.
Concept Insight: Classification of elements on the basis of increasing atomic number is known as Modern Periodic Table. The vertical columns are called groups and the horizontal rows are called periods.
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संबंधित प्रश्न
The position of eight elements in the Modern Periodic Table is given below where atomic numbers of elements are given in the parenthesis.
| Period No. | ||
| 2 | Li(3) | Be(4) |
| 3 | Na(11) | Mg(12) |
| 4 | K(19) | Ca(20) |
| 5 | Rb(37) | Sr(38) |
(i) Write the electronic configuration of Ca.
(ii) Predict the number of valence electrons in Rb.
(iii) What is the number of shells in Sr?
(iv) Predict whether K is a metal or a non – metal.
(v) Which one of these elements has the largest atom in size?
(vi) Arrange Be, Ca, Mg and Rb in the increasing order of the size of their respective atoms.
Fill in the blank in the following statement:
On going down in a group in the periodic table, the metallic character of elements ...............
Which of the following element does not lose an electron easily?
(a) Na
(b) F
(c) Mg
(d) Al
On moving from left to right in a period of the periodic table, the atomic number of elements increases. What happens to the size of atoms of elements on moving from left to right in a period?
(a) increases
(b) decreases
(c) remain the same
(d) first increases then decreases
Chorine in the periodic table is surrounded by the elements with atomic number 9, 16, 18 and 35.
Which of these have physical and chemical properties resembling chlorine.
Study the extract of the Periodic Table given below and answer the questions that follow. Give the alphabet corresponding to the element in question. DO NOT repeat an element. 
Which is an inert gas?
Fill in the blank
Oxidising property ________from fluroine to iodine because the power to accpet electron decreases.
An element A has 2 electrons in its fourth shell. State:
its valency
Supply the missing word from those in bracket:
If an element has one electron in its outermost energy level [shell] then it is likely to be _______.
Name or state following with reference to the element of the first three periods of the periodic table.
The valency of elements in group 1 [I–A].
