Question

classification of elements​

Answer 1

Answer:

elements are classified into 3 categories

1.Metel

2.Non-metel

3.Metalloids

Answer 2

Answer:

HEY THERE!!

Early Chemists - Arranged elements on basis of valency, metallic and non-metallic character.

• Method discard as elements showed variable valency and dual character.

Dobereiner [1815] - Arranged elements in increasing order of atomic weights.

• Elements were arranged in groups of three called triads.
• Atomic weight of the middle element was found generally to be the average of the other two.
• Method was discarded since it did not hold true for all elements.

Newland [1864] - Arranged elements in increasing order of atomic weights.

• Elements were arranged in a series of eight.
• Properties of every eight element was found to be a repetition of the first element.
• Method was discarded as it failed to leave spaces for undiscovered elements.

Mendeleeff [1869] - Arranged elements in increasing order of atomic weights.

• Elements were arranged in the form of a table called Mendeleef's Periodic Table.
• He stated that properties of elements were periodic functions of their atomic weights.
• Method could not justify position of certain elements, rare earths and isotopes.

Moseley [1912] - Arranged elements in increasing order of atomic numbers.

• Elements were arranged in a modified table called Modern Periodic Table.
• He stated that properties of elements were periodic function of their atomic numbers.
• Method removed most of the defects of Mendeleef's Periodic Table.