Prabin Kalikote

The increasing order of an atomic number of the elementswas the basis of the modern periodic table.

Any 4 defects in Mendeleev's periodic table are:

1. Inert gas or noble gases were absent.
2. It couldn't arrange lanthanides and actinides.
3. Its eight groups weren't divided into sub-group.
4. It couldn't arrange isotopes.
   

Any three characteristics of Mendeleev's periodic tableare:

1. It was the first scientist and systematic study of known elements.
2. It containsmany groups for undiscovered elements.
3. Properties of several elements can be studied.
   

Mendeleev's periodic table states that 'The physical &chemical properties of elements are the periodic functionof their atomic weight'.

Increasing order of atomic weight was the basis ofMendeleev's periodic table.

Newlands law of octaves stated, 'Elements whenarranged increasing order of their atomic weightsshow resemblance in physical and chemical propertiesbetween the eight and first element is similar to theeight and first notes on a musical scale.

For example, potassium is the eight element after sodium.
These elements have similar physical and chemical properties.

Dobereiner arranged elements in increasing order oftheir atomic weight in well-marked groups of three-elementcalled trides.

So, the pattern of arranging the dements in eachtriads, that the atomic weight of middle elements wasfoundto be the arithmetic mean of the atomic weights ofother two elements, called Dobereiner's law of trials.

For example

Elements: Li Na K
Atomic weight: 7 23 39

So, 23 = (7+39) / 2