1. Consider
isotopes of oxygen 16O and 18O. Would you able to place
them in Mendeleev’s periodic table?
Ans. Yes, In
Mendeleev’s Periodic table elements are arranged in the increasing order of
atomic masses. Therefore, we can place isotopes of oxygen 16O and 18O
in Mendeleev’s periodic table in two different position.
2. Find
resemblance between hydrogen and alkali metals by writing compounds of both
with chlorine, sulphur and oxygen.
Ans. Hydrogen
and other alkali metal react with non – metals (O, S and Cl),
Hydrogen
forms: H2O, H2S, HCl.
Sodium
(Alkali metal) forms: Na2O, Na2S, NaCl.
|
Compounds of
Hydrogen
|
Compounds of Sodium
|
|
HCl (Hydrogen Chloride)
H2S (Hydrogen Sulphide) H2O (Hydrogen Oxide) |
NaCl (Sodium Chloride)
Na2S (Sodium Sulphide) Na2O (Sodium Oxide) |
As
seen above compounds of hydrogen and compounds of sodium with halogen, sulphur
and oxygen have similar formulae. This is because the electronic configuration
of hydrogen resembles that of alkali metals.
3. Find out a
pair of elements from the periodic table where higher mass element is placed
before lower mass element.
Ans. 1. Argon
(40) is placed before potassium (39.1).
2. Vanadium (V) having atomic mass 50.94 is
placed before Chromium (Cr) having atomic mass 50.20.
3. Cobalt (Co) having atomic mass 58.93 is placed before Nickel (Ni) having atomic mass 58.71
