Alkali Metals

Differentiate between.Mendeleev's and the modern periodic tablePeriods and groupss-block and p-block elementsAlkali metals and halogensAlkali metals and alkaline earth metalsDuplet stable and octet...

a. Mendeleev's and the modern periodic table.

Mendeleev's	Modern
It supported the first scientific study of elements.	It is the latest and standard table of elements.
Elements were arranged with the increasing order of their atomic weight.	Elements were arranged with the increasing order of their atomic number.
It had several gaps for undiscovered elements.	Most of the elements are discovered and arranged.
It was unable to arrange isotopes.	It is able to arrange isotopes.
It didn't have lanthanides and...

Why are alkali metals most suited for photoelectric emissions?

Since the atom of alkali metal has only one valence electron, it is lightly bound with the nucleus so that the work function of alkali metal is less than that of the other metal. So the photoelectrons are easily emitted from the surface of alkali metal with visible light. On the other hand, metals such as zinc, cadmium etc. require high energy radiation (UV light) to emit photoelectrons.

Write two differences between alkali and Alkaline earth metal?

Alkali metal	alkaline earth metal
They lie in the first group and have valency 1.	They lie in second group and have valency 2.
Comparatively they are more reactive and exhibit high metallic property.	Comparatively they are less reactive and exhibit lesser metallic property.