【 】 Explain why isotopes have similar chemical properties but they differ in physical properties
Explain why isotopes have similar chemical properties but they differ in physical properties.
Answer:
Look at the isotopes of the element chlorine (₁₇Cl ) below:
³⁵Cl ³⁷Cl
The atomic number of chlorine for ³⁵Cl and ³⁷Cl isotopes is 17.That is,isotopes have the
same atomic number.
In ³⁵Cl ,the mass
number of chlorine is 35 and the mass
number of ³⁷Cl is 37.So,isotopes of an element have different mass number.
We know that mass number is the sum of the number of
protons and neutrons. If we minus
protons from mass number, we get the number of neutrons. We also know that the
number of protons is called atomic number.Furthermore,in a neutral atom,the
number of electrons is equal to numbers of protons as the charge of protons is positive
and the charge of electrons is negative.
In ³⁵Cl ,the number of neutrons(35 – 17 = 18 ) is 18.On the
other hand, in
³⁷Cl
,the number of neutrons (37 – 17 = 20 ) is 20.
So,in ³⁵Cl and ³⁷Cl isotopes of chlorine ,we are getting
different numbers of neutrons.We are getting two more neutrons in ³⁷Cl isotope.That
is why the physical property mass is more
for ³⁷Cl isotopes.
So we can say that the physical
properties of isotopes like
boiling point, melting point etc.
of an element vary due to mass
number or button numbers.
But the chemical properties of
isotopes of an element do not
vary because the number of
electrons in each isotope of that
element is equal.
We know that in a chemical change,breaking and making of bonds is involved.Electrons ,specially valence electrons are involved with these breaking and making bonds.
For ³⁵Cl and ³⁷Cl
isotopes of chlorine , the total number of electrons for both isotopes
is 17 .Chlorine is an element of group 7A .So its valence electrons will be 7 .
Actually,the chemical behavior of an
elements depends on the valence electrons of that element.Since valence
electrons of ³⁵Cl and ³⁷Cl
isotopes of chlorine are the same (7),they will show the same chemical behaviours.
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