Question

with an example of each.
Define radicals and write down their types with any four examples of each.
What is a periodic table? How many elements are discovered so far?
What is Mendeleev's periodiclaw? Listout the meritsand demerits of Mendeleevhow many elements are discovered so far ​

Answer 1

Answer:

• Today 118 elements are known to the scientific world.
• Mendeleev's periodic law : properties of elements are periodic function of their atomic masses.
• Merits : 1. Atomic masses of some elements where revised so as to give them proper place in periodic table in accordance with their properties. 2. Mendeleev kept vacant places in the periodic table for elements not discovered till then. 3. There was no place reserved for noble gases in Mendeleev original periodic table.
• Demerits : 1. The whole number atomic mass of elements cobalt and nickel is the same. Therefore, there was an ambiguity regarding their sequence in Mendeleev periodic table. 2. Isotopes world discovered long time after Mendeleev put forth the periodic table. 3. Position of hydrogen.

Explanation:

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