Structure of Atom

### Following results are observed when sodium metal is irradiated with different wavelengths. Calculate threshold wavelength and Planck’s constant.

If the threshold wavelength is $\lambda_{0} n m\left(=\lambda_{0} \times 10^{-9} \mathrm{~m}\right)$, the K.E. of the radiation would be: $h\left(\nu-\nu_{0}\right)=\frac{1}{2} m \nu^{2}$ Three...

### The work function for the caesium atom is 1.9 eV. Calculate (a) the threshold wavelength and (b) the threshold frequency of the radiation. If the caesium element is irradiated with a wavelength of 500 nm,(c) calculate the kinetic energy and the velocity of the ejected photoelectron.

Given, the work function of caesium $\left(W_{0}\right)=1.9 \mathrm{eV}$ (a)From the $W_{0}=\frac{h c}{\lambda_{0}}$ expression, we get: $\lambda_{0}=\frac{h c}{W_{0}}$ Where, $\lambda_{0}$ is the...

### In astronomical observations, signals observed from the distant stars are generally weak. If the photon detector receives a total of from the radiations of , calculate the number of photons received by the detector.

From the expression of energy of one photon (E), $E=\frac{h c}{\lambda}$ Where, $\lambda$ denotes the wavelength of the radiation $\mathrm{h}$ is Planck's constant c denotes the velocity of the...

### Neon gas is generally used in the signboards. If it emits strongly at 616 nm, calculate the number of quanta presents if it produces 2 J of energy.

No. quanta in $2 \mathrm{~J}$ of energy $\frac{2 J}{32.27 \times 10^{-20} J}$ $=6.19 \times 10^{18}$ $=6.2 \times 10^{18}$

### Neon gas is generally used in the signboards. If it emits strongly at 616 nm, calculate the frequency of emission,

Wavelength of the emitted radiation $=616 \mathrm{~nm}=616 \times 10^{-9} \mathrm{~m}$ (Given) (a)Frequency of the emission $(\nu)$ $\nu=\frac{c}{\lambda}$ Where, $c=$ speed of the radiation...

### Nitrogen laser produces radiation at a wavelength of . If the number of photons emitted is , calculate the power of this laser.

Energy with which it emits photons=Power of laser Power $=E=\frac{N h c}{\lambda}$ Where, $N=$ number of photons emitted $\mathrm{h}=$ Planck's constant $\mathrm{c}=$ velocity of radiation...

### An ion with mass number 56 contains 3 units of positive charge and more neutrons than electrons. Assign the symbol to this ion.

Let us consider the total no. electrons present in $A^{3+}$ be $x$. Now, total no. neutrons in it $=x+30.4 \%$ of $x=1.304 x$ Since the ion has a charge of $+3, \Rightarrow$ no. electrons in neutral...

### An ion with mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than the electrons, find the symbol of the ion.

The number of electrons in a negatively charged ion  be $x$. Then, no. neutrons present $=x+11.1 \%$ of $x=x+0.111 x=1.111 x$ No. electrons present in the neutral atom $=(x-1)$ (When an ion carries...

### An element with mass number 81 contains 31.7% more neutrons as compared to protons. Assign the atomic symbol.

Let us consider that the  No.of protons in the element be $x$. No. of  neutrons  $=x+31.7 \%$ of $x$ $=x+0.317 x$ $=1.317 x$ According to the question, Mass number of the element $=81$, which...

### Symbols and can be written, whereas symbols and are not acceptable. Answer briefly.

The general convention followed while representing elements along with their atomic masses (A), and their atomic numbers $(Z)$ is ${ }_{Z}^{A} \mathrm{X}$. Therefore, ${ }_{35}^{79} \mathrm{Br}$ is...

### In Rutherford’s experiment, generally the thin foil of heavy atoms, like gold, platinum etc. have been used to be bombarded by the α-particles. If the thin foil of light atoms like Aluminium etc. is used, what difference would be observed from the above results?

The findings obtained with a foil made up of heavy atoms will differ from those obtained with a foil made up of comparatively light atoms. The magnitude of positive charge in the nucleus of a...

### What transition in the hydrogen spectrum would have the same wavelength as the Balmer transition n = 4 to n = 2 of He+ spectrum?

The wave number associated with the Balmer transition for the He+ ion (n = 4 to n = 2 ) is given by: $\bar{\nu}=\frac{1}{\lambda}=R Z^{2}\left(\frac{1}{n_{1}^{2}}-\frac{1}{n_{2}^{2}}\right)$...

### Show that the circumference of the Bohr orbit for the hydrogen atom is an integral multiple of the de Broglie wavelength associated with the electron revolving around the orbit.

Only one electron exists in hydrogen atoms. The angular momentum of this electron, according to Bohr's postulates, is: $m v r=n \frac{h}{2 \pi} \quad \ldots .(1)$ Where, $n=1,2,3, \ldots$ As per de...

### How many electrons in an atom may have the following quantum numbers?a) n = 4, ​ b)n = 3, l = 0

(a)The total number of electrons in the atom =$2n^2$ if n is the primary quantum number. Hence, For n = 4, Total no. electrons = 2 (16) = 32 An atom with 32 electrons has the following electron...

### Using s, p and d notations, describe the orbital with the following quantum numbers. (a)n = 1, l = 0; (b)n = 3; l =1 (c) n = 4; l = 2; (d) n = 4; l =3.

(a)n = 1, l = 0 implies a 1s orbital. (b)n = 3 and l = 1 implies a 3p orbital. (c)n = 4 and l = 2 implies a 4d orbital. (d)n = 4 and l = 3 implies a 4f orbital.

### (I)An atomic orbital has n = 3. What are the possible values of l and ml ? (II)List the quantum numbers (ml and l) of electrons for 3d orbital. (III) Which of the following orbitals are possible? 1p, 2s, 2p and 3f

(I) The range of potential values for 'l' is 0 to (n – 1). As a result, the possible values of l for n = 3 are 0, 1, and 2. The total number of potential ml = (2l + 1) values. It has a range of...

### Give the number of electrons in the species ,

The number of electrons in H2 is 1 + 1 = 2. 2 – 1 = 1 number of electrons in H2+ H2: The number of electrons in H2 equals 1 + 1 = 2. Number of electrons in O2 = 8 + 8 = 16. In O2+, the number of...

### 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.

(i)No.protons = no.electrons in a neutral atom. The number of protons in the atoms of the element is 29. (ii)The electronic configuration of this element (atomic number 29) is 1s...

### An electron is in one of the 3d orbitals. Give the possible values of n, l and ml for this electron.

For the 3d orbital: Principal quantum number ,possible values (n) = 3 Azimuthal quantum number, possible values(l) = 2 Magnetic quantum number ,possible values(ml) = – 2, – 1, 0, 1, 2

### Calculate the wavelength of an electron moving with a velocity of

As per de Broglie’s equation, $\lambda=\frac{h}{m v}$ Where, $\lambda$ denotes thr wavelength of the moving particle $\mathrm{m}$ is the mass of the particle $v$ denotes the velocity of the...

### Write the complete symbol for the atom with the given atomic number (Z) and atomic mass (A) (I)Z = 17, A = 35 (II)Z = 92, A = 233 (III)Z = 4, A = 9

(i)$${}_{17}^{35}C$$ (ii)$${}_{92}^{233}C$$ (iii)$${}_{4}^{9}C$$

### (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 mg of 14C. (Assume that mass of a neutron = 1.675 × 10–27 kg). (iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH3 at STP. Will the answer change if the temperature and pressure are changed?

(i) 1 molecule of methane contains 10 electrons (6 from carbon, 4 from hydrogen) Therefore, 1 mole of methane contains 10*NA = 6.022*1024 electrons. (ii) Number of neutrons in 14g (1 mol) of 14C =...

### How many neutrons and protons are there in the following nuclei?

Ans:  24 is the mass number. The number of protons in an atom equals the number of atoms in the atom. Mass number – Atomic number = 24 – 12 = 12 neutrons Numerical value of mass nubmer = 56 Number...

### How many neutrons and protons are there in the following nuclei?

Ans:  Carbon-13 mass number = 13 Carbon atomic number = number of protons in a single carbon atom = 6 As a result, the total number of neutrons in a carbon atom is calculated as follows: mass number...

### (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 mg of 14C. (Assume that mass of a neutron = 1.675 × 10–27 kg). (iii) Find (a) the total number and (b) the total mass of protons in 34 mg of NH3 at STP. Will the answer change if the temperature and pressure are changed?

Ans: (i) 1 molecule of methane contains 10 electrons (6 from carbon, 4 from hydrogen) Therefore, 1 mole of methane contains 10*NA = 6.022*1024 electrons. (ii) Number of neutrons in 14g (1 mol)...

### (i) Calculate the number of electrons which will together weigh one gram. (ii) Calculate the mass and charge of one mole of electrons.

Ans: 1 electron weighs 9.109*10-31 kg. Therefore, number of electrons that weigh 1 g (10-3 kg) = 10-3kg/9.109*10-31 kg = 1.098*1027 electrons (ii) Mass of one mole of electrons = NA* mass of one...

### Assertion (A): It is impossible to determine the exact position and exact the momentum of an electron simultaneously. Reason (R): The path of an electron in an atom is clearly defined.

(i) Both A and R are true and R is the correct explanation of A. (ii) Both A and R are true and R is not the correct explanation of A. (iii) A is true and R is false. (iv) Both A and R are false....

### Assertion (A): All isotopes of a given element show the same type of chemical behaviour. Reason (R): The chemical properties of an atom are controlled by the number of electrons in the atom.

(i) Both A and R are true and R is the correct explanation of A. (ii) Both A and R are true but R is not the correct explanation of A. (iii) A is true but R is false. (iv) Both A and R are false....

### Match species are given in Column 1 with the electronic configuration given in Column 2.

Column 1 Column 2 (i) Cr   (a) [Ar]3d84s0   (ii) Fe2+   (b) [Ar]3d104s1   (iii) Ni2+   (c) [Ar]3d64s0   (iv) Cu   (d) [Ar] 3d54s1     (e) [Ar]3d64s2     Column 1 Column 2 (i) Cr    (d) [Ar]...

### Match the following

Column 1 Column 2 (i) Photon (a)Value is 4 for N shell (ii) Electron (b)Probability density (iii) ψ2 (c)Always a positive value (iv) The principal quantum number n   (d)Exhibits both momentum...

### Match the following

Column 1 Column 2 (i) X-rays (a) ν = 100-0 104 Hz (ii) UV (b) ν = 1010Hz (iii) Long radio waves (c) ν = 1016 Hz (iv) Microwave (d) ν = 1018Hz   Column 1 Column 2 (i) X-rays (d) ν = 1018Hz (ii) UV...

### Match the following

Rule Principle (i) Hund’s Rule   (a) No two electrons in an atom can have the same set of four quantum numbers. (ii) Aufbau Principle   (b) Half-filled and filled orbitals have extra stability....

### Match the quantum numbers with the information provided by these Quantum number Information provided

Column 1 Column 2 (i) Principal quantum number (a) orientation of the orbital (ii) Azimuthal quantum number (b) energy and size of orbital (iii) Magnetic quantum number (c) spin of an electron (iv)...

### Match the following species with their corresponding ground state electronic configuration.

Atom / Ion Electronic configuration (i) Cu (a) 1s2 2s2 2p6 3s2 3p6 3d10 (ii) Cu2+ (b) 1s2 2s2 2p6 3s2 3p6 (iii) Zn2+ (c) 1s2 2s2 2p6 3s2 3p6 3d10 4s1 (iv) Cr3+ (d) 1s2 2s2 2p6 3s2 3p63d9   (e) 1s2...

### The hydrogen atom has only one electron, so mutual repulsion between electrons is absent. However, in multielectron atoms mutual repulsion between the electrons is significant. How does this affect the energy of an electron in the orbitals of the same principal quantum number in multielectron atoms?

Hydrogen atom has only one electron, so the mutual repulsion between the electrons is non-existent. However, in multielectron atoms the interaction between electrons is important. This is because,...

### A hypothetical electromagnetic wave is shown in Figure. Find out the wavelength of the radiation.

Distance between the two identical successive points in a wave is called the wavelength. Given, In the hypothetical wave, Wavelength, λ = 4 × 2.16 pm Hence, Wavelength, λ = 8.64 pm.

### Chlorine exists in two isotopic forms, Cl-37 and Cl-35 but its atomic mass is 35.5. This indicates the ratio of Cl-37 and Cl-35 is approximately

(i) 1:2 (ii) 1:1 (iii) 1:3 (iv) 3:1     Correct Answer: (iii) 1:3 Explanation: Ratio of isotope abundance of Chlorine 37 to Chlorine 35 = A1​:A2​ Ratio of isotope abundance of Chlorine 37...

### Orbital angular momentum depends on __________.

(i) l (ii) n and l (iii) n and m (iv) m and s Correct Answer: (i) l Explanation: Orbital angular momentum depends on the value of l which is referred to as the azimuthal quantum number.

### A total number of orbitals associated with the third shell will be __________.

(i) 2 (ii) 4 (iii) 9 (iv) 3     Correct Answer: (iii) 9 Explanation: The total number of orbitals in nth shell = n2 Hence, the total number of orbitals associated with the third shell will...

### The number of radial nodes for 3p orbital is __________.

(i) 3 (ii) 4 (iii) 2 (iv) 1     Correct Answer: (iv) 1 Explanation: Number of radial nodes for 3p orbital = 3−1−1 Number of radial nodes for 3p orbital = 3−2 Number of radial nodes for 3p...

### Two atoms are said to be isobars if.

(i) they have the same atomic number but a different mass number. (ii) they have the same number of electrons but a different number of neutrons. (iii) they have the same number of neutrons but a...

### Which of the following properties of an atom could be explained correctly by Thomson Model of an atom?

(i) Overall neutrality of atom. (ii) Spectra of a hydrogen atom. (iii) Position of electrons, protons and neutrons in an atom. (iv) Stability of atom.     Correct Answer: (i) Overall...

### Which of the following statements about the electron is incorrect?

(i) It is a negatively charged particle. (ii) The mass of an electron is equal to the mass of a neutron. (iii) It is a basic constituent of all atoms. (iv) It is a constituent of cathode rays....

### Which of the following statement is not correct about the characteristics of cathode rays?

(i) They start from the cathode and move towards the anode. (ii) They travel in a straight line in the absence of an external electrical or magnetic field. (iii) Characteristics of cathode rays do...

### The probability density plots of 1s and 2s orbitals are given in Figure:

The density of dots in a region represents the probability density of finding electrons in the region. Based on the above diagram which of the following statements is incorrect? (i) 1s and 2s...