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प्रश्न
Write a scientific reason.
There was ambiguity about the correct position of hydrogen in Mendeleev’s periodic table.
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उत्तर
- Hydrogen resembles alkali metals. It has one electron in its outermost shell like alkali metals. Its valency is 1 like alkali metals. It forms oxides (H2O) similar to alkali metals (Na2O). However, hydrogen also resembles halogens. It is a diatomic molecule (H2) like halogens (F2, Cl2). It is one electron deficient to achieve stable electronic configuration similar to halogens.
- Due to this unique behaviour of hydrogen, it could not be decided whether the correct position of hydrogen is in the group of alkali metals or in the group of halogens.
Thus, there was ambiguity about the correct position of hydrogen in Mendeleev's periodic table.
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संबंधित प्रश्न
In the Modern Periodic Table, calcium (atomic number 20) is surrounded by elements with atomic numbers 12, 19, 21, and 38. Which of these have physical and chemical properties resembling calcium?
Fill in the following blank with suitable word:
The horizontal rows in a periodic table are called ...............
Give two example of group 1 elements.
Explain why all the elements of a period have different chemical properties.
In what respects do the properties of group 1 elements differ from those of group 17 elements? Explain with examples by taking one element from each group.
The atomic numbers of the three elements X, Y and Z are 2, 6 and 10 respectively.
(i) Which two elements belong to the same group?
(ii) Which two elements belong to the same period?
Give reasons for your choice.
Answer the following in respect of element `31/15 P `
To which group and period does it belong?
Fill in the blank:
The horizontal rows in the periodic table are called _____________.
Name an alkali metal in period 3 and halogen in period 2.
Name the noble gas with 3 shells.
State the main aim of classifying elements. Which is the more fundamental property of elements that is used in the development of Modern Periodic Table? Name and state the law based on this fundamental property. On which side of the periodic table one can find metals, non-metals and metalloids?
State the modern periodic law for the classification of elements. How many (i) groups and (ii) periods are there in the modern periodic table?
An element E has following electronic configuration:
|
K |
L |
M |
|
2 |
8 |
6 |
(a) To which group of the periodic table does element E belong?
(b) To which period of the periodic table does element E belong?
(c) State the number of valence electrons present in element E.
(d) State the valency of the element E.
An element A has 2 electrons in its fourth shell. State its electronic configuration.
Give the symbol and valency of the following element and radical.
Potassium
Give the symbol and valency of the following element and radical.
Chlorine [Chloride]
Give the symbol and valency of the following element and radical.
Nitrate
Give the chemical formula of sodium sulphite
Give the chemical formula of calcium phosphate
Compare Modern Periodic Law with Mendeleev's Periodic Law.
Which of the following statements about the Modern periodic table is correct?
Right or wrong sentence.
The modern periodic table shows the molecular masses of the elements in each frame.
Write a scientific reason.
Lithium and sodium are included in the same group in the periodic table.
Distinguish between:
s-block - p-block
State whether true or false. If false, correct the statement.
Lanthanides and actinides are kept at the bottom of the periodic table because they resemble each other but they do not resemble with any other group elements.
State any five features of modern periodic table.
______ is the longest period in the periodical table.
On moving from left to right in a period in the periodic table, the size of the atom ______
In the modern periodic table, elements are arranged according to their ______
Choose an element from period 3 of modern periodic table that matches the description given below in instance. Give a reason for your choice.
It has same valency as Lithium.
The maximum number of electrons that can be accommodated in s, p,d, and f subshells are ______.
Spot the error:
There are 5 periods and 17 groups in the modern periodic table.
A part of modern periodic table is given below. On its basis, answer the following questions:
| Group No. → | 1 | 2 | 13 | 14 | 15 | 16 | 17 | 18 |
| Period ↓ | ||||||||
| 2 | A | B | ||||||
| 3 | E | D | F | C |
Which of the element is a Metalloid?
Explain giving reason why although the nuclear charge in atoms increases in moving from left to right in a period as well as in moving from top to bottom in a group in the Modern periodic table, but the size of the atoms does not vary similarly in both situations.
Select the appropriate options and complete the following paragraph:
(metals, non-metals, metalloids, four, seven, s-block, p-block, d-block, f-block).
On the basis of electronic configuration, elements in the modern periodic table are classified Into ______ blocks. Groups 1 and 2 elements are included in ______ and all these elements are metals. (except Hydrogen). Group 13 to 18 elements are included in ______. This block contains metals, non-metals and metalloids. Group 3 to 12 elements are included in ______ and all the elements are ______ elements shown at the bottom of the periodic table i.e. Lanthanides and Actinides constitute ______ and all these elements are metals.
Name the metalloids in the first twenty elements.
Name the following metal:
A metal present in period 3, group 1 of the periodic table.
Match the atomic number with the following:
A rare gas.
