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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
Fill in the following blank with suitable word:
Group 1 elements are called ...............
The atomic numbers of four elements P, Q, R and S are 6, 8, 14 and 16 respectively. Out of these, the element known as metalloid is:
(a) P
(b) Q
(c) R
(d) S
Which of the following statement is correct in regard to the classification of elements?
(a) Elements in modern periodic table are arranged on the basis of increasing atomic masses.
(b) Elements in Mendeleev's periodic table are arranged on the basis of increasing atomic numbers.
(c) In modern periodic table, the element nickel of lower atomic mass is kept before the element cobalt of higher atomic mass.
(d) In modern periodic table, the isotopes of chlorine having different atomic masses are kept in the same group.
State whether the following statement is true or false:
On going down in a group of the periodic table, the number of valence electrons increases.
What is the fundamental difference in the electron configurations between the group 1 and group 2 elements?
What is the main characteristic of the last elements in the periods of the periodic table? What is the general name of such elements?
What are the merits of the modern periodic table of elements?
Helium and neon are unreactive gases. What, if anything, do their atoms have in common?
What are the periods in a periodic table? Give two characteristics of each.
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.
What are horizontal rows and vertical columns in a periodic table known as?
An element barium has the atomic number 56. Look up its position in the periodic table and answer the following question.
Is it larger or smaller than caesium (Cs)?
Name an alkali metal in period 3 and halogen in period 2.
Name the noble gas with 3 shells.
What is the number of elements in the 3rd period, of the modern periodic table?
Two elements P and Q belong to the same period of the modern periodic table and are in group 1 and group 2, respectively. Compare the following characteristics in the tabular form.
- Number of electrons in their atoms
- Their tendency to lose electrons
- Their metallic characters
- Formation of their oxides
- Formulae of their chlorides
Give the symbol and valency of the following element and radical.
Potassium
Give the symbol and valency of the following element and radical.
Aluminium
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.
Nitrate
Give the symbol and valency of the following element and radical.
Bisulphite
Name the following:
The group of the Modern Periodic Table to which calcium [Ca2+] belongs.
State the number of elements in Period 2 of the Periodic Table.
What are the periods in a periodic table?
Which of the following statements about the Modern periodic table is correct?
The d-block elements are called as _______ elements.
Group 13 to 18 : p block : : _______ : d block
The modern periodic table shows the molecular masses of the elements in each frame.
The K and L shells of the elements Na and Mg contain electrons.
Noble gases belong to______ group of the periodic table.
Which of these belong to the same period?
| Element | A | B | C |
| Atomic number | 2 | 10 | 5 |
The amount of energy released when one or more electrons is added to the neutral atom is ______
Which of the following statements about the Modern Periodic Table is correct:
An element which is an essential constituent of all organic compounds belongs to
Arrange the following elements in the increasing order of their metallic character
| Mg, | Ca, | K, | Ge, | Ga |
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.
An element ‘M' has 50% of the electrons filled in the 3rd shell as in the 2nd shell. The atomic number of ‘M’ is ______.
