Which of he following blocks of elements comprises transition elements
s
p
d
f
boron
Which three elements are in the same triad in Dobereiner’s system of classification of elements?
Li, Ca, Br
Sr, Ca, Ba
Na, I, K
Cl, Sr, K
An isotope which is used in the treatment of cancer?
Iodine
cobalt
Chlorine
Uranium
Newlands arranged the known elements in the order of their
increasing atomic masses
decreasing atomic masses
increasing atomic numbers
decreasing atomic numbers
According to Mendeleev’s periodic table, the oxide of which of the following elements bears the formula RO2?
Silicon
Sodium
Magnesium
Aluminium
