Calculate number of protons and neutrons from isotopes of Oxygen 16O, 17O, and 18O. The atomic number of Oxygen is 8.
Solution:
The Atomic Number (Z) of Oxygen is 8. The atomic number is always equal to the number of protons. And the number of protons always equals the electron number in an uncharged atom so that the atom is electrically neutral.
Therefore, an uncharged Oxygen atom always has 8 protons and 8 electrons.
An isotope is formed when the neutron number varies in an atom of the same element. This changes the mass number in an atom’s nucleus since the mass number A is the sum of protons and neutrons. The proton number remains unchanged.
mass number A= Number of protons (p) + number of neutrons (n)
The mass number is written as a superscript next to the element’s symbol as,
So, the number of neutrons in different Oxygen isotopes 16O, 17O, and 18O is-
16O Isotope:
Mass number =16 (Given)
mass number (A) = number of protons (p) + number of neutrons (n)
A= p+ n
Therefore, n= A-p = 16-8 = 8.
Solution using log table-
n = A-p
Applying log10 on both sides
log10 n = log (A-Z)
log10 n = log10 (16-8) = log10 8 = 0.9031
Applying antilog,
n = Antilog (0.9031) = 8
The number of neutrons in the 13N Isotope is 8, and the number of protons is 8.
17O Isotope:
Mass number = 17 (Given)
mass number (A) = number of protons (p) + number of neutrons (n)
A= p+ n
Therefore, n= A-p = 17-8 = 9.
Solution using log table-
n = A-p
Applying log10 on both sides
log10 n = log (A-Z)
log10 n = log10 (17-8) = log10 9 = 0.9542
Applying antilog,
n = Antilog (0.9542) = 9
The number of neutrons in the 17O Isotope is 9, and the number of protons is 8.
18O Isotope:
Mass number =17 (Given)
mass number (A) = number of protons (p) + number of neutrons (n)
A= p+ n
Therefore, n= A-p = 18-8 = 10.
Solution using log table-
n = A-p
Applying log10 on both sides
log10 n = log (A-Z)
log10 n = log10 (18-8) = log10 10 = 1
Applying antilog,
n = Antilog (1) = 10
The number of neutrons in the 18O Isotope is 10, and the number of protons is 8.