Structure of Atom Test

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Structure of Atom Test - 54

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Weekly Quiz Competition

Question 1
1 / -0

Energy of the third orbit of Bohr's atom is:

A
$$-13.6$$ eV

B
$$-3.4$$ eV

C
$$-1.5$$ eV

D
none of these

Solution

$$E_n = - 13.6\times(z^2/n^2)eV$$
$$E_3 = - 13.6\times1/9eV$$
$$ = - 1.5eV$$
Question 2
1 / -0

Which element with lowest atomic number .

A
$$_{19}K$$

B
$$_{24}Cr$$

C
$$_{11}Na$$

D
$$_{29}Cu$$

Solution

The atomic number is defined as the number of protons present in an element.

In sodium atom, the number of protons present = $$11$$

So, its atomic number is $$11$$

Which is least from the rest of the given elements.

Hence, the correct option is $$C$$
Question 3
1 / -0

What is the ratio of time periods $$(\dfrac{T_1}{T_2})$$ in $$2^{nd}$$ orbit of hydrogen atom to third orbit of $$He^+$$ ion?

A
$$\dfrac{8}{27}$$

B
$$\dfrac{32}{27}$$

C
$$\dfrac{27}{32}$$

D
$$\dfrac{27}{8}$$

Solution

$$\dfrac{T_H}{T_{He}}=\dfrac{n_1^3t_2^2}{n_2^3t_1^2}$$

$$= \dfrac{8\times4}{3^3}=\dfrac{32}{27}$$

The ratio is $$32:27$$.
Question 4
1 / -0

The carbonate of a metal is isomorphous (similar formula) with magnesium carbonate and contains 6.091 percent of carbon. The atomic weight of metal is:

A
24

B
56

C
137

D
260

Solution

Let the formula of unknown carbonate= $$XCO_3$$

Molecular weight= $$x+12+48=(60+x)gmol^{-1}$$

% of composition of carbon= $$\left [\dfrac{12}{(60+x)} \right]\times 100$$

$$\Rightarrow 6.091= \cfrac {12}{60+x}\times 100$$

$$\Rightarrow 0.06091(60+x)=12$$

$$\Rightarrow x=137.01$$

$$\therefore$$ The atomic weight of metal is $$137 g/mol$$.

Hence, option $$C$$ is correct.
Question 5
1 / -0

A single electron orbits a stationary nucleus of charge $$+Z$$, where $$Z$$ is a constant. It requires 47.2 eV to excite electron from second Bohr orbit to third Bohr orbit, find the value of $$Z$$.

A
1

B
3

C
5

D
4

Solution

Position is $$n_1=2 \ \Rightarrow n_2=3$$ and $$\Delta E=47.2eV$$
We have $$\Delta E=13.6z^2(\dfrac{1}{n_1^2}− \dfrac{1}{n_2^2})eV$$
$$47.2=13.6z^2(\dfrac{1}{2^2}− \dfrac{1}{3^2})$$
$$z=5$$
Question 6
1 / -0

Multiple of fine structure of spectral lines is due to:

A
presence of main energy levels

B
presence of sub-level

C
presence of electronic configuration

D
is not a characteristics of the atom.

Solution

It is because of sub energy levels. Previously the energy of sub energy levels was considered to be equal but it actually differs by about $$10^{-4}$$ eV. Hence fine spectral lines are observed
Question 7
1 / -0

If the speed of electrons in Bohr's first obtain of hydrogen is $$'X'$$ the speed of electrons in third orbit is:

A
$$\dfrac {X}{9}$$

B
$$\dfrac {X}{3}$$

C
$$3X$$

D
$$9X$$

Solution

We know,
$$v = v_0 z/n$$ here $$ v_0 = X = $$ velocity of elctron in first orbit of hydrogen or velocity constant
for third orbit of hydrogen atom value of n is 3 and z is 1
So $$ v = \dfrac{X }{3}$$
Question 8
1 / -0

What happens to the atomic number during a chemical reaction?

A
It increases.

B
It changes.

C
Remains the same.

D
Changes alternatively.
Question 9
1 / -0

Which of the following parameters are not same for all hydrogen like atoms and ions in their state?

A
Radius of orbit

B
Speed of electron

C
Energy of the atom

D
Orbital angular momentum of electron

Solution

As we know,

$$r \propto n^2$$

$$E \propto -\dfrac{z^2}{n^2}$$

$$V\propto \dfrac{z}{n}$$

$$mur=nh^2 \pi$$

So, independent of $$z$$ so it will remain same.
So, orbital angular momentum of electron
Question 10
1 / -0

Boron has 2 stable isotopes, $$10-B$$$$(19$$%) and $$11-B$$($$81$$%) the atomic mass that should appear for boron in the periodic table is:

A
$$10.8$$

B
$$10.2$$

C
$$11.2$$

D
$$10.0$$

Solution

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Re-Attempt Weekly Quiz Competition

Structure of Atom Test - 54

Result

Structure of Atom Test - 54

Score

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SHARING IS CARING

Question 1

$$-13.6$$ eV

$$-3.4$$ eV

$$-1.5$$ eV

none of these

Solution

Question 2

$$_{19}K$$

$$_{24}Cr$$

$$_{11}Na$$

$$_{29}Cu$$

Solution

Question 3

$$\dfrac{8}{27}$$

$$\dfrac{32}{27}$$

$$\dfrac{27}{32}$$

$$\dfrac{27}{8}$$

Solution

Question 4

24

56

137

260

Solution

Question 5

1

3

5

4

Solution

Question 6

presence of main energy levels

presence of sub-level

presence of electronic configuration

is not a characteristics of the atom.

Solution

Question 7

$$\dfrac {X}{9}$$

$$\dfrac {X}{3}$$

$$3X$$

$$9X$$

Solution

Question 8

It increases.

It changes.

Remains the same.

Changes alternatively.

Question 9

Radius of orbit

Speed of electron

Energy of the atom

Orbital angular momentum of electron

Solution

Question 10

$$10.8$$

$$10.2$$

$$11.2$$

$$10.0$$

Solution

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