## Explain, giving reasons, which of the following sets of quantum numbers are not possible.

[question] Question. Explain, giving reasons, which of the following sets of quantum numbers are not possible. (a) $n=0 I=0 m_{\imath}=0$ $m_{s}=+\frac{1}{2}$ (b) $n=1 I=0 m_{\imath}=0$ $m_{x}=-\frac{1}{2}$ (c) $n=1 I=1 m_{l}=0$ $m_{x}=+\frac{1}{2}$ (d) $n=2 l=1 m i=0$ $m_{x}=+\frac{1}{2}$ (e) $n=3 I=3 m_{l}=-3$ $m_{x}=+\frac{1}{2}$ (f) $n=3 I=1 m_{l}=0$ $m_{x}=+\frac{1}{2}$ [/question] [solution] Solution: (a) The given set of quantum numbers is not possible because the value of the principal q...

## Using $s, p, d$ notations, describe the orbital with the following quantum numbers.

[question] Question. Using s, p, d notations, describe the orbital with the following quantum numbers. (a) $n=1, I=0 ;$ (b) $n=3 ; I=1$ (c) $n=4 ; I=2 ;$ (d) $n=4 ; I=3$ [/question] [solution] Solution: (a) $n=1, I=0$ (Given) The orbital is $1 s$. (b) For $n=3$ and $I=1$ The orbital is $3 p$. (c) For $n=4$ and $I=2$ The orbital is $4 d$. (d) For $n=4$ and $I=3$ The orbital is $4 f$. [/solution]...

## An atom of an element contains 29 electrons and 35 neutrons. Deduce

[question] Question. An atom of an element contains 29 electrons and 35 neutrons. Deduce (i) the number of protons and (ii) the electronic configuration of the element. [/question] [solution] Solution: (i) For an atom to be neutral, the number of protons is equal to the number of electrons. Number of protons in the atom of the given element = 29 (ii) The electronic configuration of the atom is $1 s^{2} 2 s^{2} 2 p^{6} 3 s^{2} 3 p^{6} 4 s^{2} 3 d^{10}$ [/solution]...

## An electron is in one of the 3d orbitals

[question] Question. An electron is in one of the $3 d$ orbitals. Give the possible values of $n, I$ and $m_{1}$ for this electron. [/question] [solution] Solution: For the $3 d$ orbital: Principal quantum number $(n)=3$ Azimuthal quantum number $(I)=2$ Magnetic quantum number $\left(m_{i}\right)=-2,-1,0,1,2$ [/question]...

## What is the lowest value of n that allows g orbitals to exist?

[question] Question. What is the lowest value of n that allows g orbitals to exist? [/question] [solution] Solution: For $\mathrm{q}$-orbitals, $I=4$. As for any value ' $n$ ' of principal quantum number, the Azimuthal quantum number $(I)$ can have a value from zero to $(n-1)$. $\therefore$ For $I=4$, minimum value of $n=5$ [/solution]...

## Write the electronic configurations of the following ions:

[question] Question. (i) Write the electronic configurations of the following ions: (a) $\mathrm{H}^{-}$ (b) $\mathrm{Na}^{+}$ (c) $\mathrm{O}^{2-}$ (d) $\mathrm{F}^{-}$ (ii) What are the atomic numbers of elements whose outermost electrons are represented by (a) $3 s^{1}$ (b) $2 p^{3}$ and (c) $3 p^{5} ?$ (iii) Which atoms are indicated by the following configurations? (a) $[\mathrm{He}] 2 s^{1}$ (b) [Ne] $3 s^{2} 3 p^{3}$ (c) $[\mathrm{Ar}] 4 s^{2} 3 d^{1}$. [/question] [solution] Solution: (i...

## Calculate the wavelength,

[question] Question. Calculate the wavelength, frequency and wave number of a light wave whose period is $2.0 \times 10^{-10} \mathrm{~s} .$ [/question] [solution] Solution: Frequency $(v)$ of light $=\frac{1}{\text { Period }}$ $=\frac{1}{2.0 \times 10^{-10} \mathrm{~s}}=5.0 \times 10^{9} \mathrm{~s}^{-1}$ Wavelength $(\lambda)$ of light $=\frac{c}{v}$ Where $c=$ velocity of light in vacuum $=3 \times 10^{8} \mathrm{~m} / \mathrm{s}$ Substituting the value in the given expression of $\lambda$ :...

## Write the complete symbol for the atom with thegiven atomic numbe

[question] Question. Write the complete symbol for the atom with thegiven atomic number (Z) and Atomic mass (A (i)Z = 17, A = 35 (ii)Z = 92, A = 233 (iii)Z = 4, A = 9 [/question] [solution] Solution: (i) ${ }_{17}^{35} \mathrm{Cl}$ (ii) ${ }_{92}^{233} \mathrm{U}$ (iii) ${ }_{4}^{9} \mathrm{Be}$ [/solution]...

## Calculate the total number of electrons present in one mole of methane

[question] Question. (i)Calculate the total number of electrons present in one mole of methane (ii) Find (a) the total number and (b) the total mass of neutrons in $7 \mathrm{mg}$ of ${ }^{14} \mathrm{C}$. (Assume that mass of a neutron $=1.675 \times 10^{-27} \mathrm{~kg}$ ). (iii) Find (a) the total number and (b) the total mass of protons in $34 \mathrm{mg}$ of $\mathrm{NH}_{3}$ at STP. Will the answer change if the temperature and pressure are changed? [/question] [solution] Solution: (i) Nu...

## Calculate the number of electrons which will together weigh one gram

[question] Question. (i)Calculate the number of electrons which will together weigh one gram. (ii)Calculate the mass and charge of one mole of electrons [/question] [solution] Solution: (i) Mass of one electron $=9.10939 \times 10^{-31} \mathrm{~kg}$ $\therefore$ Number of electrons that weigh $9.10939 \times 10^{-31} \mathrm{~kg}=1$ $\therefore$ Number of electrons that will weigh $1 \mathrm{~g}\left(1 \times 10^{-3} \mathrm{~kg}\right)$ \$=\frac{1}{9.10939 \times 10^{-31} \mathrm{~kg}} \times\l...