Three elements Q, R and T have mass number 40. Their atoms contain 22, 21 and 20 neutrons respectively.
Three elements Q, R and T have mass number 40. Their atoms contain 22, 21 and 20 neutrons respectively. Represent their atomic composition with appropriate symbol.
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Mass number (A) = Number of protons (Z) + Number of neutrons (N).
A = Z + N
∴ Z = A – N
For the given three elements,
A = 40.
Values of their atomic numbers Z, are calculated from the given values of the number of neutrons, N, using the above formula.
For Q :
Z = A – N
= 40 – 22
= 18
For R :
Z = A – N
= 40 – 21
= 19
For T :
Z = A – N
= 40 – 20
= 20
Now,
Atomic composition of an element (X) is represented as \(_Z^AX\).
The atomic compositions of the three elements are written as follows :
\(_{18}^{40}Q,\)\(_{19}^{40}R,\)\(_{20}^{40}T\)
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