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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
In the Modern Periodic Table, which are the metals among the first ten elements?
How many rows and columns are there in the modern periodic table?
How does the metallic character of elements in Modern Periodic Table vary on moving from left to right in a period, and (ii) down a group?Give reason to justify your answer.
Write the merits of the modern periodic table over Mendeleev’s Periodic table
where should hydrogen be placed in the modern periodic table? Give reason for your answer.
On which side of the periodic table will you find non-metals?
Which of the following statement about the modern periodic table is correct?
(a) It has 18 horizontal rows known as periods.
(b) It has 7 vertical columns known as periods.
(c) It has 18 vertical columns known as groups.
(d) It has 7 horizontal rows known as groups.
The atomic particle whose number in the atoms of an element always remains the same and which forms the real basis for the modern classification of elements is:
(a) electron
(b) proton
(c) neutron
(d) meson
What is a period in a periodic table?
On the basis of electronic configuration, how will you identify chemically similar elements?
What is the usual number of valence electrons and valency of group 18 elements of the periodic table?
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.
Define:
Periodic table
Correct the statement.
Transition elements are placed at extreme right of the periodic table.
Name two elements in Inert gas.
Name two elements in each case:
Actinides
How will the tendency to gain electrons change as we go from left to right across a period? Why?
Write a short note.
Position of isotopes in the Mendeleev’s and the modern periodic table.
What would be the correct order if Zn, Fe, Al and Cu are arranged in increasing order of reactivity?
What is the number of elements in the 1st period?
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
Answer the following question.
How it can be proved that the basic structure of the Modern Periodic Table is based on the electronic configuration of atoms of different elements?
Give the symbol and valency of the following element and radical.
Calcium
Give the chemical formula of sodium nitrate
Fill in the blank:
The element lithium in the Modern Periodic Table with valency 1+ belongs to the group ______.
p-block is composed of groups 1 and 2.
The K and L shells of the elements Na and Mg contain electrons.
Distinguish between:
s-block - p-block
State any five features of modern periodic table.
An element which is an essential constituent of all organic compounds belongs to
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- X has 12 protons and 12 electrons
- Y has 12 protons and 10 electrons
An element X which is a yellow solid at room temperature shows catenation and allotropy. X forms two oxides which are also formed during the thermal decomposition of ferrous sulphate crystals and are the major air pollutants.
- Identify the element X
- Write the electronic configuration of X
- Write the balanced chemical equation for the thermal decomposition of ferrous sulphate crystals?
- What would be the nature (acidic/ basic) of oxides formed?
- Locate the position of the element in the Modern Periodic Table.
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.
Noble gases are placed in the ______ group in the modern periodic table.
Spot the error:
There are 5 periods and 17 groups in the modern periodic table.
Name the metalloids in the first twenty elements.
Answer the following in respect of element \[\ce{_16^32S}\].
Give its formula with hydrogen.
