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प्रश्न
Write a short note.
Position of isotopes in the Mendeleev’s and the modern periodic table.
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उत्तर
Isotopes: Isotopes are the atoms having the same atomic number but different atomic masses.
Therefore, according to Mendeleev’s classification, these should be placed at different places depending upon their atomic masses.
For example, hydrogen isotopes with atomic masses 1,2 and 3 should be placed at three places. However, isotopes have not been given separate places in the periodic table because of their similar properties. So this was a drawback of Mendeleev's periodic table as he could not explain the position of isotopes.
The modern periodic table is based upon the arrangement of the elements on the basis of their atomic number. So, all the isotopes of hydrogen should be placed at the same place depending upon their atomic number.
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संबंधित प्रश्न
What is periodicity in properties of elements with reference to the Modern Periodic Table?
On which side of the periodic table will you find non-metals?
What is the name of those elements which divide metals and non-metals in the periodic table?
Explain why, the noble gases are placed in a separate group.
The modern periodic table was prepared by ______.
Which element has two shells, both of which are completely filled with electrons?
Which element has the electronic configuration 2, 8, 2?
Consider the following elements:
Ca, Cl, Na, I, Li, Ba, Sr, K, Br
Separate these elements into three groups (families) of similar properties. State one property in each case on the basis of which you have made your choice.
How would the tendency to lose electrons change as we go from left to right across a period of the periodic table?
What is the number of valence electrons in the atoms of first elements in a period?
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.
An element X belongs to 3rd period and group 2 of the periodic table. State:
(a) number of valence electrons
(b) valency
(c) metal or non-metal
(d) name of the element
Define:
Periodic table
What are horizontal rows and vertical columns in a periodic table known as?
Name two elements in each case: Lanthanides
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?
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.
How many periods and groups are there in the modern periodic table?
An element A has 2 electrons in its fourth shell. State its electronic configuration.
Define the atomic size.
Give the symbol and valency of the following element and radical.
Calcium
Give the symbol and valency of the following element and radical.
Chlorine [Chloride]
Give the symbol and valency of the following element and radical.
Bisulphate
Give the chemical formula of carbonic acid
Give the chemical formula of calcium phosphate
State the number of elements in Period 3 of the Periodic Table.
Group 13 to 18 : p block : : _______ : d block
The modern periodic table has 1 to 7 periods.
Distinguish between:
Group 17 - Group 18
The longest period of the Modern Periodic Table is period.
If an element X is placed in group 14, what will be the formula and the nature of bonding of its chloride?
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.
Spot the error:
The elements of group 13 are called the carbon family.
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.
An element ‘M' has 50% of the electrons filled in the 3rd shell as in the 2nd shell. The atomic number of ‘M’ is ______.
Name two elements that you would expect to show chemical reactions similar to calcium. What is the basis of your choice?
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?
