(a) The modern periodic table has been evolved through the early attempts of
Dobereiner, Newland and Mendeleev. List one advantage and one limitation of
all the three attempts.
(b) Name the scientist who first of all showed that atomic number of an element is a
more fundamental property than its atomic mass.
(c) State Modern periodic law.
Answers
Answer:
DOBEREINIER-It's advantage is, he discovered that if he place three elements on basis on increasing atomic masses, then the chemical properties are similar. Also, the mass of the middle element is the arithmetic mean of the other two elements.
It's disadvantage is that he can only make 3 triads, and failed to arrange other elements in form of triads
NEWLAND-It's advantage is that he discovered that if the elements are arranged in order of increasing atomic masses, then the chemical property of every eighth element is repetition of it's first element.
it's limitation is that he can only arranged elements upto calcium. After calcium, every 8th element doesnot posses chemical property of it's first element
MENDELEEV- It's advantage is that, the periodic table can accommodate noble gases when they were discovered.
It's limitation is that, the periodic table does mentioned the position of isotopes
(b) It's Henry Moseley
(c) The properties of element is the periodic function of it's atomic number.
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