Atomic Number and Mass Number

Predict the possible atomic number(s) of an atom in which the third shell is incompletely filled and maximum $4$ more electrons can be added to that shell of the atom.

A natural sample of an element contains two isotopes A and B. The difference in their atomic mass is $2$ units. If the percentage abundance of the lighter isotope A is $25\%$ and its atomic mass is y, calculate the average atomic weight.

Based on the information given in the below three statements, answer the following question.

(i) Element X has two valence electrons in the M-shell.
(ii) In element Y, the electrons are distributed in the first three shells. It has eight electrons in the M-shell.
(iii) Element Z has eight electrons in the penultimate shell, i.e., M.

What are the number of electrons and protons present in Y?

From the following table, identify isotopes and isobars.

The electronic configuration of an atom A is $\mathrm{a}, \mathrm{a}+\mathrm{b}, \mathrm{a}+2\mathrm{b}, \mathrm{a}$ and that of B is $\mathrm{a}, \mathrm{a}+\mathrm{b}, 3\mathrm{a}+2\mathrm{b}, \mathrm{b}$. If the number of neutrons in A is $5\mathrm{b}$ and that in B is $22.5\mathrm{a}$, calculate their mass numbers.

The electronic configuration of an atom A is $\mathrm{a}, \mathrm{a}+\mathrm{b}, \mathrm{a}+2\mathrm{b}, \mathrm{a}$ and that of B is $\mathrm{a}, \mathrm{a}+\mathrm{b}, 3\mathrm{a}+2\mathrm{b}, \mathrm{b}$. Calculate their atomic numbers.

The number of protons in A and B are $\mathrm{x}$ and $\mathrm{x}-2$ respectively while that of neutrons in A and B are $\mathrm{y}$ and $\mathrm{y}+2$ respectively. What conclusion can you draw regarding A and B from the given information?

The ratio of the number of neutrons present in the two element X and Y is $5 : 7$ and the ratio of mass numbers is $10 : 13$. Element X attains stable octet configuration by losing two electrons from the fourth shell. Calculate the number of protons, electrons and neutrons present in X and Y.

If the average atomic mass of chlorine $35.5$, then find the percentage abundance of the two isotopes of chlorine which have the mass number $35$ and $37$.

The number of electrons in a di-positive ion of an element X is $18$. If the mass number of X is $4$ units more than twice the number of electrons of its ion, calculate of protons, electron and neutrons in X.

Nuclear charge of an element B is twice that of A. If A has two completely filled orbits and L shell is its outermost orbit, find out atomic numbers of A and B.

A metallic element forms an ion with unit charge. The ion has $10$ electrons and $12$ neutrons . What is the number of electrons, protons and neutrons in its neutral atom? Represent the atom with atomic number and mass number.

A dipositive ion has an electronic configuration of $2, 8, 8$. Find out the number of electrons, protons and neutrons in that element if its mass number is $40$.

The percentage abundance of two isotopes of boron in a natural sample are $99$ and $1$. The first isotope has $6$ neutrons in the nucleus. If the actual atomic mass of boron is $11.01$, calculate the mass numbers of the two isotopes.

Mass number of two isotopes of an element differ by $2$ units $\left(\mathrm{A} \mathrm{and} \mathrm{A}+2\right)$. Average atomic mass is $0.5$ more than the lower mass number. What could be the ratio of the two isotopes?

A stable dispositive ion and a dinegative ion are isoelectronic. What is the difference between their mass numbers if the number of neutrons in both the atoms is equal to their atomic numbers?

A neutral atom of an element has a nucleus with nuclear charge $12$ times and mass $24$ times that of hydrogen. Calculate the number of electrons, protons and neutrons in its stable positively charged ion.

An atom of an element has mass number $31$. It has $16$ neutrons. The valence shell and the number of valence electrons, respectively, could be

The atoms of the same element may differ in the number of _____.

Arrange the following statements in a sequence which involves the calculation of atomic number and mass number of an atom of an element with $15$ electrons and $16$ neutrons.

$\left(1\right)$ $\mathrm{A}=\mathrm{Number} \mathrm{of} \mathrm{protons} + \mathrm{Number} \mathrm{of} \mathrm{Neutrons}$

$$\begin{gathered} \mathrm{A}=\mathrm{Z} + \mathrm{Number} \mathrm{of} \mathrm{neutrons} \\ \mathrm{A}= 15 + 16 =31 \end{gathered}$$

$\left(2\right)$ Number of protons and number of electrons are equal in a neutral atom. Hence, the atomic number Z is equal to $15$.

$\left(3\right)$ Mass number is equal to the total number of protons and neutrons.

$\left(4\right)$ Atomic number is $15$ and mass number is $31$.