Question

Can the following groups of elements be classified as Dobereiner's triad?
a) Na, Si, Cl
a) Be, Mg, Ca
b) Li,Na, K

Answer 1

Answer:

DOBERENIER'S TRIAD states that three elements arranged by him for ex.let them be x,y,and z then,at.mass of( x and y )/2=at.mass of z

a.)Si,Na,Cl

at.mass Na=23

at.mass Si= 28.08

at.mass Cl=35.5

28.08( ) 23+35.5/2

28.08 ( ) it is 29

i. e,almost equal but their properties do not match

Na is metal,Cl is a non metal , Si is metalloid

Valency of Si do not match and their chemical properties also differ,therefore answer is NO

b.)similarly,calculating them ,at.mass of Mg(24.3)and the mean of at mass of Be (9)and Ca(40)is 24 almost and their properties also match each ,valency is 2 and are alkali metals,so they also are of DOBENEINER'S triads and is YES

c.)similarly, Li ,Na and K all are representative elements of periodic table each valency is 1 ,all are alkali metals and mean of atomic masses of Potassium and Lithium

i.e,22.9 it's almost equal to at.mass of Na i.e,22.9 so it is a perfect triad for dobereiner and the answer is YES