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प्रश्न
Write 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
The position of three elements A, B and C in the Periodic Table are shown below –
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Group 16
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Group 17
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A
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B
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C
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(a) State whether A is a metal or non-metal.
(b) State whether C is more reactive or less reactive than A.
(c) Will C be larger or smaller in size than B?
(d) Which type of ion, cation or anion, will be formed by element A?
Write the merits of the modern periodic table over Mendeleev’s Periodic table
Give two example of group 17 elements.
Give two example of group 18 elements.
The modern periodic table was prepared by ______.
Consider the following elements:
Na, Ca, Al, K, Mg, Li
Which of these elements belong to the same group of the periodic table?
Which element has the electronic configuration 2, 8, 2?
How does the chemical reactivity of alkali metals vary on going in group 1 of the periodic table?
What is the usual number of valence electrons and valency of group 18 elements of the periodic table?
What is the main characteristic of the last elements in the periods of the periodic table? What is the general name of such elements?
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.
State the term
The tabular arrangement of elements in horizontal rows and vertical columns _________
Name the type of elements which have outermost shell incomplete.
Write the number of protons, neutrons and electronic configuration of \[\ce{_19^39K, _15^31P}\]. Also state their position in periodic table.
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.
How many periods and groups are there in the modern periodic table?
Name and state the following with reference to the elements of the first three periods of the periodic table.
A covalent compound formed by an element in period 2 and a halogen.
Define the atomic size.
Name the cation and the anion in the salt – calcium sulphate
Give the symbol and valency of the following element and radical.
Hydrogen
Give the symbol and valency of the following element and radical.
Chlorine [Chloride]
Give the symbol and valency of the following element and radical.
Sulphur [Sulphide]
Give the symbol and valency of the following element and radical.
Bicarbonate
Give the chemical formula of ammonium sulphate
Fill in the blank:
The element lithium in the Modern Periodic Table with valency 1+ belongs to the group ______.
State the number of elements in Period 1 of the Periodic Table.
p-block is composed of groups 1 and 2.
Position of A, B and C three elements is given in the table from the modern periodic table. Answer the following questions.
| Periods | Group 2 | Group 17 |
| 2 | ----- | A |
| 3 | B | ----- |
| 4 | ----- | C |
- What is A element metal or nonmetal?
- Which is the outermost orbit of element B?
- Identify C element and it's physical state.
Elements in the modern periodic table are arranged in ______groups and______ periods.
______ forms the basis of the modern periodic table.
______ and ______ are called inner transition elements.
How does the property vary in periods and in groups?
Which of these belong to the same period?
| Element | A | B | C |
| Atomic number | 2 | 10 | 5 |
The longest period of the Modern Periodic Table is period.
What is the symbol of the element Tungsten?
Which of the following elements would lose an electron easily?
An element with atomic number ______ will form a basic oxide.
A group of elements in the periodic table is given below (Boron is the first member of the group and Thallium is the last).
Boron, Aluminium, Gallium, Indium, Thallium
Answer the following question in relation to the above group of elements:
If the electronic configuration of aluminium is 2, 8, 3, how many electrons are there in the outer shell of thallium?
