Structure of Atom Test

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Structure of Atom Test - 26

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Weekly Quiz Competition

Question 1

1 / -0

The total number of neutrons in all isotopes of hydrogen is equal to:

6

2

4

3 Solution

Hydrogen has 3 isotopes.

$$_{1}^{1}\textrm{H} $$	$$_{1}^{2}\textrm{H}$$	$$_{1}^{3}\textrm{H}$$
neutron 0	1	2
proton 1	1	1

The total number of neutrons in all the isotopes of Hydrogen $$=0+1+2=3$$.

Question 2
1 / -0

Determine the element if its ground state has 13 electrons in its "M-shell".

A
Copper

B
Manganese

C
Nickel

D
Iron

Solution

The M shell is the third energy level; the first (K) shell can contain only 2 electrons. The second (L) shell can contain up to 8 electrons, for a total of 10. The third (M) shell can contain up to 18 electrons, but when it gets to 10, the fourth or N shell starts to fill up, since its first two electrons have lower energy than the next energy level in the M shell, so we have 18 electrons in the K, L, and M shells and the next two go into the N shell (for element 20, or calcium). So calcium has 10 electrons in the M shell and two in the N shell; then the next electrons go into the M shell (the 3d orbitals) so when we get to a total of 25 electrons, we have 10 in the K & L shells, two in the N shell, and 13 in the M shell. If it is a neutral atom, the element has atomic number 25, that is, manganese
Question 3
1 / -0

The atomic numbers of elements X,Y and Z are 19, 21 and 25 respectively. The order of number of electrons present in the M shells of these elements ______________.

A
Z>X>Y

B
X>Y>Z

C
Z>Y>X

D
Y>Z>X

Solution

X-19: $${1s}^{2}, {2s}^{2} {2p}^{6}, {3s}^{2} {3p}^{6} {4s}^{1}$$, here M shell is 3rd energy level which contain 8 electrons $${3s}^{2} {3p}^{6}$$
Y-21: $${1s}^{2}, {2s}^{2} {2p}^{6}, {3s}^{2} {3p}^{6} {4s}^{2}{3d}^{2}$$, here M shell indicates 3rd enegy level which contain 9 electrons $${3s}^{2} {3p}^{6}{3d}^{1}$$
Z-25: $${1s}^{2}, {2s}^{2} {2p}^{6}, {3s}^{2} {3p}^{6} {4s}^{2}{3d}^{5}$$, here M shell indicates 3rd energy level which contain 13 electrons $${3s}^{2} {3p}^{6}{3d}^{5}$$
So, here Z contains more electrons in M shell than Y and than X. So the order is Z>Y>X.
Question 4
1 / -0

A sample of rock from moon contains equal number of atoms of uranium and lead $$(\mathrm{t}_{\frac{1}{2}}$$ for $$\mathrm{U}=4.5\times 10^{9}$$ years $$)$$. The age of the rock would be

A
$$4.5\times 10^{9}$$ years

B
$$9\times 10^{9}$$ years

C
$$13.5\times 10^{9}$$ years

D
$$2.25\times 10^{9}$$ years

Solution

$$ t_{1/2}=\frac{0.693}{k} $$
$$ \therefore k=\frac{0.693}{45x10^{g}}years^{-1} $$
It is an uranium dating technique,
$$ \therefore Age=\frac{2.303}{K}log_{10}[1+\frac{Pb^{206}}{U^{238}}] $$
$$ =\frac{2.303}{0.693}x45x10^{g}log_{10}[1+1] $$
$$ =\frac{2.303x45x10^{g}}{0.693}log_{10}(2) $$
Age = 4 x 10$$ ^{g} $$ years
Question 5
1 / -0

The main defect of Bohr's atom model is :

A
mixing of classical and quantum theories

B
exclusion of nuclear motion

C
failed to explain the fine structure of spectral lines

D
failed to explain larger atoms

Solution

Bohr's model can only clearly explain hydrogen or hydrogen-like atoms, it fails when applied to larger and heavier atoms like iron, gold, mercury, etc.
Question 6
1 / -0

The maximum number of electrons that can be filled into all the orbitals corresponding to the azimuthal quantum number $$l$$ = 3, is:

A
$$14$$

B
$$15$$

C
$$12$$

D
$$18$$

Solution

For $$l=3$$, possible values of $$m=2l+1=7$$. For each m, there can be 2 electrons filled.

Maximum number of electrons, thus $$=2 \times 7=14$$.
Question 7
1 / -0

After the completion of $$np^{6}$$ electronic configuration, the next orbital will be filled by:

A
(n+1)d

B
(n+1)s

C
(n+1)f

D
none of the above

Solution

As per Aufbau's principle, the orbital next to np is (n+1)s.
Question 8
1 / -0

For an element (Z=25), how many electrons are present in the "N" shell in its ground state?

A
$$13$$

B
$$2$$

C
$$15$$

D
$$3$$

Solution

25 is atomic number of Manganese.
Electronic Configuration: $$[Ar] 4s^2 3d^5$$
So, there are 2 electrons in the fourth(Nth) shell.
Question 9
1 / -0

The number of electrons in an element $$X$$ is 15 and the number of neutrons is 16. The element can be represented as :

A
$$\begin{matrix}31\\ 15\end{matrix} X$$

B
$$\begin{matrix}31\\ 16\end{matrix} X$$

C
$$\begin{matrix}16\\ 15\end{matrix} X$$

D
$$\begin{matrix}15\\ 16\end{matrix} X$$

Solution

$$^{A}_{Z}{X}$$, where A stands for the atomic mass number which is the sum of protons and neutrons in the atom of an element and Z stands for an atomic number of the element which is the number of electrons in an atom of an element.

Atomic mass $$=$$ Number of electrons + Number of neutrons

Atomic number $$=$$ Number of protons $$=$$ Number of electrons

Therefore, atomic mass $$= 15 + 16 = 31$$ and atomic number is $$= 15$$.
Question 10
1 / -0

Identify the correct statements.
(i) Atomic number = number of protons + number of electrons
(ii) Mass number = number of protons + number of neutrons
(iii) Atomic mass = number of protons = number of neutrons
(iv) Atomic number = number of protons = number of electrons

A
(i) and (ii)

B
(i) and (iii)

C
(ii) and (iii)

D
(ii) and (iv)

Solution

The atomic number of an element is the number of protons (positive charge) which is also equal to the number of electrons (negative charge) as the atom is always electrically neutral.

Since the mass of an atom is concentrated in the nucleus of the atom, its mass number is the total number of sub-atomic particles which are present in the nucleus. Protons and neutrons together are called nucleons.

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Structure of Atom Test - 26

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Structure of Atom Test - 26

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Question 1

6

2

4

3

Solution

Question 2

Copper

Manganese

Nickel

Iron

Solution

Question 3

Z>X>Y

X>Y>Z

Z>Y>X

Y>Z>X

Solution

Question 4

$$4.5\times 10^{9}$$ years

$$9\times 10^{9}$$ years

$$13.5\times 10^{9}$$ years

$$2.25\times 10^{9}$$ years

Solution

Question 5

mixing of classical and quantum theories

exclusion of nuclear motion

failed to explain the fine structure of spectral lines

failed to explain larger atoms

Solution

Question 6

$$14$$

$$15$$

$$12$$

$$18$$

Solution

Question 7

(n+1)d

(n+1)s

(n+1)f

none of the above

Solution

Question 8

$$13$$

$$2$$

$$15$$

$$3$$

Solution

Question 9

$$\begin{matrix}31\\ 15\end{matrix} X$$

$$\begin{matrix}31\\ 16\end{matrix} X$$

$$\begin{matrix}16\\ 15\end{matrix} X$$

$$\begin{matrix}15\\ 16\end{matrix} X$$

Solution

Question 10

(i) and (ii)

(i) and (iii)

(ii) and (iii)

(ii) and (iv)

Solution

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