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Chemistry 1 Marks Question

Structure of Atom · MP Board (MPBSE) STD 11 Science (Madhya Pradesh - English Medium). 88 questions.

Questions · Page 2 of 2

1 Marks Question

Question 511 Mark
What is the value of Bohr's radius for the first orbit of hydrogen atom?
Answer
$\text{r}_1=0.529\mathring{\text{A}}=0.529\times10^{-10}\text{m}$
$=5.29\times10^{-11}\text{m}$
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Question 531 Mark
What do you mean by saying that energy of the electron is quantised?
Answer
This means that the electrons in an atom have only definite values of energies.
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Question 541 Mark
What is the possible value of angular momentum quantum number (l) for the unpaired electron in the atom of an element whose atomic number is 17?
Answer
l = 1 for unpaired electron of Cl(17):
$1\text{s}^2\ 2\text{s}^2\ 3\text{s}^2\ 3\text{p}^2_\text{x}\ 3\text{p}^2_\text{v}\ 3\text{p}^1_\text{z}.$
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Question 551 Mark
In which atom, the outermost electron can have the following set of quantum numbers?) $n=3, I=0, m_l=0, m_s$ $=\frac{-1}{2}$
Answer
$\mathrm{n}=3$ and $\mathrm{I}=0$ means the last electron enters in 3 s -orbital. Thus, the complete configuration upto 3 is $1 \mathrm{~s}^2, 2 \mathrm{~s}^2, 2 \mathrm{p}^6$, $3 s^1$ Total number of electrons,
$=2+2+6+1=11$. Thus, the element is sodium.
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Question 571 Mark
What physical meaning is attributed to the square of the absolute value of wave function, $|\psi|^2?$
Answer
$|\psi|^2$ shows the probability of finding the electron at a point with coordinates (x, y, z).
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Question 581 Mark
Write the difference between atomic mass and atomic mass number?
Answer
Atomic mass is the mass of all the sub-atomic particles present in an atom, mainly proton and neutrons as electron have negligible mass. Atomic mass number is equal to sum of number of protons and neutrons.
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Question 591 Mark
Write a cation and an anion which is isoelectronic with Ar. (Atomic number of Ar = 18]
Answer
$\mathrm{Ca}^{2+}$ is cation and $\mathrm{Cl}^{-}$ion is ions which are isoelectronic with Ar.
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Question 601 Mark
Cs shows maximum photo electric effect, why?
Answer
It is alkali metal with large size, lowest ionisation enthalpy i.e. lowest work function.
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Question 611 Mark
How many orbitals are present in 'g' sub-shell?
Answer
9 orbitals. Because for 'g' orbital, l = 4, m = -4, -3, -2, -1, 0, +1, +2, +3, +4
9 values of 'm' means 9 type of orbitals.
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Question 621 Mark
How many electrons and protons are present in the anion of $\mathrm{Li}_3 \mathrm{N}$ ?
Answer
$\mathrm{N}^{3-}$ is anion which has 7 protons and 10 electrons.
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Question 631 Mark
How does the intensity of the spectral line vary with wavelength?
Answer
As the wavelength decreases, intensity also decreases.
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Question 641 Mark
$\mathrm{CI}, \mathrm{Cl}^{-}$ have same atomic number or mass number or both? Explain.
Answer
They have same atomic number as well as mass number. It is because they differ in number of electrons but have same number of protons and neutrons. Atomic number (Z) = Number of protons, Mass number = Number of protons + Number of neutrons.
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Question 651 Mark
Write electronic configuration of $\mathrm{Ni}^{2+}($ Atomic number of $\mathrm{Ni}=28)$.
Answer
$1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^8 .[\because$ Electrons are removed from 4s orbital first, then from 3d]
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Question 661 Mark
i. What is difference between 'I' and 'L'?
ii. Nitrogen has 7 protons, 7 electrons, 7 neutrons. Calculate the number of electrons, Protons and neutrons in $\mathrm{N}^{3-} ion.$
Answer
i. 'I' represents azimuthul quantum number which determines shape of orbital e.g. I = 0 is sorbital (spherical)
   'L' represents $2^{\text {nd }}$ shell or orbit or energy level.
ii. $\mathrm{N}^{3-}$ is formed when ' N ' atoms gains 3 electrons

Number of electrons in $\mathrm{N}^{3-}=7+3=10$ electrons
Proton in $\mathrm{N}^{3-}=7$
Neutrons in $\mathrm{N}^{3-}=7$
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Question 671 Mark
Which one of the atomic orbital has higher energy?
  1. n = 3,1 = 2, m = +1,
  2. n = 4, 1 = 0, m = 0.
Answer
  1. 3d has higher energy,
  2. 4s orbital.
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Question 681 Mark
How does change in velocity of a moving particle alter the wavelength of the particle?
Answer
$'\lambda'$ (wavelength) decreases with increase in velocity of moving particle, i.e $\lambda=\frac{\text{h}}{\text{mV}}.$
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Question 691 Mark
The electronic configuration of N (7) is $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^1_\text{x}\ 2\text{p}^1_\text{y}\ 2\text{p}^1_\text{z}$ and not $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^2_\text{x}\ 2\text{p}^1_\text{y}.$Why?
Answer
N(7) has electronic configuration $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^1_\text{x}\ 2\text{p}^1_\text{y}\ 2\text{p}^1_\text{z}$ and not $1\text{s}^2\ 2\text{s}^2\ 2\text{p}^2_\text{x}\ 2\text{p}^1_\text{y},$ because latter violates Hund's rule which states degenerate (having equal energy) orbitals are first singly filled and then pairing starts so as to avoid repulsion.
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Question 701 Mark
Write electronic configuration of $\mathrm{Cu}^{2+}(29), \mathrm{Cr}^{3+}(24)$.
Answer
$\mathbf{C u}^{2+}(\mathbf{2 9}): 1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^9$
$\mathbf{C r}^{3+}(24): 1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^0 ~3 d^3$
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Question 711 Mark
An electron is in one of the 3 d-orbitals. Give the possible values of n, I and m, for this electron.
Answer
For 3d electron, n = 3, 1 = 2, m = -2, - 1, 0, +1, + 2
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Question 721 Mark
Which series of hydrogen spectrum lies in:
  1. Visible region,
  2. UV region?
Answer
  1. Balmer series,
  2. Lyman series.
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Question 741 Mark
How many electrons are present in $\text{NO}^-_3?$
Answer
$\text{NO}^-_3$ ion has 7 + 8 3 + 1 = 7 + 24 + 1 = 32 electrons.
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Question 751 Mark
Neutron or proton of same wavelength, which will have more velocity?
Answer
Proton will have more velocity due to smaller mass.
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Question 761 Mark
How many unpaired electrons are present in N(7)? Name the principle which explains the presence of these unpaired electrons.
Answer
$\text{N}(7):1\text{s}^2\ 2\text{s}^2\ 2\text{p}^1_\text{x}\ 2\text{p}^1_\text{y}\ 2\text{p}^1_\text{z},$ there are 3 unpaired electrons due to Hund's rule.
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Question 771 Mark
Name the element whose isotope has mass number 14 and having 8 neutrons.
Answer
Atomic number = Mass number - Number of neutrons,
Atomic number = 14 - 8 = 6, so the element is carbon.
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Question 781 Mark
What happens to the position and momentum of an electron if a photon of a short wavelength hits the electron?
Answer
The uncertainty in position decreases but the uncertainty in velocity or momentum increases if the wavelength of photon is short.
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Question 801 Mark
What is the difference between a quantum and a photon?
Answer
The smallest packet of energy of any radiation is called a quantum whereas that of light is called a photon.
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Question 821 Mark
Can we apply Heisenberg's uncertainty principle to a stationary electron? Why or why not?
Answer
No, because velocity = 0 and thus, position can be measured accurately.
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Question 831 Mark
Why does a cannot seem to travel in the form of a wave although de-Broglie relation is applicable to it?
Answer
This is because in this case wavelength is negligible as the mass of car is very high and wavelength is inversely proportional to mass.
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Question 841 Mark
Write the name of non-directional orbital.
Answer
s-orbital is spherically symmetrical, i.e. non-directional.
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Question 861 Mark
What is the difference in the angular momentum of an electron present in 3p and 4p orbitals?
Answer
Angular momentum ‘l’ of 3p and 4p orbitals will be same because I = 1 for p orbital.
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Question 871 Mark
Why is energy of electron negative?
Answer
When electron is at infinite distance from nucleus, its energy is zero. When it is brought near to the nucleus, energy becomes less than zero, i.e. negative due to force of attraction between nucleus and electron.
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Question 881 Mark
What are four quantum numbers of $19^{th}$ electron of copper?
Answer
Cu(29): $1 s^2 ~2 s^2 ~2 p^6 ~3 s^2 ~3 p^6 ~4 s^1 ~3 d^{10}$
n = 4, l = 0, m = 0, s $=\frac{+1}{2}$
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1 Marks Question - Page 2 - Chemistry STD 11 Science Questions - Vidyadip