Advertisements
Advertisements
प्रश्न
Write the merits of Mendeleev’s periodic table.
उत्तर
- Atomic masses of some elements were revised so as to give them a proper place in the periodic table in accordance with their properties. For example, the previously determined atomic mass of beryllium, 14.09, was changed to the correct value of 9.4, and beryllium was placed before boron.
- Mendeleev kept vacant places in the periodic table for elements not discovered till then. Three of these unknown elements were given the names eka-boron, eka-aluminum and eka-silicon from the known neighbours and their atomic masses were indicated as 44, 68 and 72, respectively. Not only this but their properties were also predicted. Later on, these elements were discovered and named scandium (Sc), gallium (Ga) and germanium (Ge) respectively. The properties of these elements matched well with those predicted by Mendeleev. See the table given below. Due to this success, all were convinced about the importance of Mendeleev’s periodic table and this method of classification of elements was accepted immediately.
Actual and predicted properties of galliumProperty eka-aluminum (E)
(Mendeleev’s prediction)Gallium (Ga)
(actual)1. Atomic mass 68 69.7 2. Density (g/cm3) 5.9 5.94 3. Melting point (°C) Low 30.2 4. Formula of chloride ECl3 GaCl3 5. Formula of oxide E2O3 Ga2O3 6. Nature of oxide Amphoteric oxide Amphoteric oxide - There was no place reserved for noble gases in Mendeleev’s original periodic table. However, when noble gases such as helium, neon and argon were discovered towards the end of the nineteenth century, Mendeleev created the ‘zero’ group without disturbing the original periodic table in which the noble gases were fitted very well.
APPEARS IN
संबंधित प्रश्न
Name two elements that have two electrons in their outermost shells.
Element X forms a chloride with the formula XCl2, which is a solid with a high melting point. X would most likely be in the same group of the Periodic Table as
On what basis elements are arranged in periodi table now?
What chemical properties of elements were used by Mendeleev in creating his periodic table?
(a) Write its electronic configuration and determine its valency.
(b) Is it more reactive or less reactive than Ca (atomic number 20)? Justify your answer giving reason.
(c) Is it a metal or a non-metal?
(d) Write the formula of its oxide.
List two contrasting visible characters of garden pea Mendel used for his experiment.
Explain in brief how Mendel interpreted his results to show that the traits may be dominant or recessive.
Write a short note.
Mendeleev’s periodic law.
Mendeleev's contributions to the concept of a periodic table laid the foundation for the Modern Periodic Table. Give reasons.
State Mendeleev's periodic law.
Use Mendeleev's Periodic Table to predict the formula of hydrides of carbon and silicon.
Which group of elements was missing from Mendeleev's original periodic table?
Answer the following question:
Name two elements having a single electron in their outermost shell.
How did Mendeleev arrange the elements in the periodic table?
What was the basis of Mendeleev's classification?
In Mendeleev’s periodic table eka- silicon was later named as _______.
Beryllium : alkaline earth metal : : sodium: _______
Write the molecular formula of the oxide of any one of the elements in Mendeleev’s periodic table.
Write scientific reason.
Mendeleev kept vacant places in the periodic table.
What physical and chemical properties of elements did Mendeleev consider in compiling the periodic table?
What are the limitations of Mendeleev's periodic table?
In Mendeleev’s Periodic Table, gaps were left for the elements to be discovered later. Which of the following elements found a place in the Periodic Table later?
The properties of eka-aluminum predicted by Mendeleev are the same as the properties of a later discovered elements: ______
Which of the following oxide is most basic?
Which of the following properties does not match the element of the halogen family?
According to Mendeléev's Periodic Law, the elements were arranged in the periodic table in the order of
Which of the following statement (s) about the Modern Periodic Table are incorrect
- The elements in the Modern Periodic Table are arranged on the basis of their decreasing atomic number
- The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic masses
- Isotopes are placed in adjoining group (s) in the Periodic Table
- The elements in the Modern Periodic Table are arranged on the basis of their increasing atomic number
On moving from left to right in a period in the periodic table, the size of the atom.
In Mendeléev’s Periodic Table the elements were arranged in the increasing order of their atomic masses. However, cobalt with atomic mass of 58.93 amu was placed before nickel having an atomic mass of 58.71 amu. Give reason for the same.
Write the formulae of chlorides of Eka-silicon and Eka-aluminium, the elements predicted by Mendeléev.
Which group of elements could be placed in Mendeléev's Periodic Table without disturbing the original order? Give reason.
