In a Dobereiner’s triad, the respective atomic masses of the first and the last elements are 40.1 u and 137.3 u.What is the mass of the middle element of the triad?
177.5 u
128.2u
87.6 u
48.9u
The second period of the modern periodic table comprises
2 elements
8 elements
18 elements
36 elements
One element M is in the 13th group, formula of its chloride is
MCl
MCl2
MCl 3
M2Cl3
Which of he following blocks of elements comprises transition elements
s
p
d
f
Which of an element is more important to chemist than atomic mass?
Atomic number
chemical property
physical property
Shape
In which alternative are the numbers of periods and groups in the modern periodic table correctly listed?
The first element of period has valence electron of
1
2
3
0
Elements with which of following atomic number will be non metalloid in character
12
20
13
16
