Structure of Atom Test

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Structure of Atom Test - 23

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Weekly Quiz Competition

Question 1
1 / -0

By knowing the number of protons in a neutral atom, one can determine :

A
the identity of the element.

B
the number of neutrons in the atom.

C
the number of common isotopes of the element.

D
the atomic radius size.

Solution

$$(A)$$ the identity of the element.

In a neutral atom, the number of protons is always the atomic number of the element and uniquely identifies the element. and in this, the number of positive protons and negative electrons is always equal.
Question 2
1 / -0

Who proposed the planetary model of the atom?

A
Earnest Rutherford

B
Max Planck

C
Neils Bohr

D
James Chadwick

E
J.J. Thompson

Solution

Neils Bohr proposed the planetary model of the atom in 1913 that the electrons revolve in a fixed orbit around the nucleus just as all the planets revolve around the sun in solar system.
Question 3
1 / -0

A neutral atom has $$12$$ electrons and $$13$$ neutrons. Its mass number is:

A
$$12$$

B
$$24$$

C
$$13$$

D
$$25$$

Solution

Mass = number of electrons/protones + number of neutrons
= $$ 12 + 13 = 25 $$
Question 4
1 / -0

Atomic number of element ___________ is $$19$$.

A
$$Mg$$

B
$$K$$

C
$$Ar$$

D
$$Ca$$

Solution

Atomic number of potassium (K) is 19.
Atomic numbers of Mg, Ar and Ca are 12, 18 and 20 respectively.
Question 5
1 / -0

Plum Pudding Model of the Atom was given by:

A
Thomson

B
Rutherford

C
Bohr

D
Chadwick

Solution

J. J. Thomson's model was also known as the plum pudding model according to which positive charge is distributed uniformly throughout the atom and negative charge is dispersed in it.

Hence, the correct option is $$A$$
Question 6
1 / -0

How much energy would be required by an electron while moving from ground state to 3rd excited state in $$H{e^ + }$$ ion

A
40.8 ev

B
10.2 ev

C
51 ev

D
35 ev

Solution

3rd excited state means 4th orbit
Question 7
1 / -0

According to Bohr's model of hydrogen atom, relation between principal quantum number n and radius of stable orbit is

A
$$r \propto \frac{1}{n}$$

B
$$r \propto n$$

C
$$r\propto\frac{1}{n^2}$$

D
$$r\propto n^2$$

Solution

Let an electron (mass m), is revolving around nucleus of a hydrogen atom in an orbit of radius $$r$$ with velocity $$v$$. Electron gets centripetal force to revolve, from the electrostatic attraction force between electron and nucleus,
$$\dfrac{mv^{2}}{r}=\dfrac{e\times e}{4\pi\varepsilon_{0}r^{2}}$$ (for H- atom, $$Z=1$$ hence charge on nucleus is $$=e$$)
  $$mv^{2}=\dfrac{e^{2}}{4\pi\varepsilon_{0}r}$$ ...................eq1

According to Bohr's model, angular momentum of electron :
$$mvr=\dfrac{nh}{2\pi}$$ ..................eq2

Now, squaring eq2 and dividing by eq1, we get
  $$\dfrac{mv^{2}r^{2}}{mv^{2}}=\dfrac{n^{2}h^{2}4\pi\varepsilon_{0}r}{4\pi^{2}e^{2}}$$

  $$r=\dfrac{n^{2}h^{2}\varepsilon_{0}}{\pi me^{2}}$$

which gives $$r\propto n^{2}$$
Question 8
1 / -0

What idea states that lower energy level orbitals will be filled with electrons before higher energy level orbitals?

A
Pauli's exclusion principle

B
Octet rule

C
Aufbau principle

D
Hund's rule

Solution

Aufbau's rule/principle states that the sub shell and orbitals of lower energy must be filled first before higher energy levels. The energy is proportional to $$(n+l)$$ value. Thus answer for question is option C.
Question 9
1 / -0

A neutral atom of fluorine has a mass number of $$19$$ and an atomic number of $$9$$. How many neutrons does it have?

A
$$10$$

B
$$9$$

C
$$19$$

D
$$28$$

E
It is impossible to determine from the information given.

Solution

Mass number, $$A=19$$
Atomic number, $$Z=9$$
Number of neutrons=$$A-Z=19-9=10$$
Question 10
1 / -0

Number of electrons surroundings Kr in $$Kr{F_2}$$ is:

A
$$10$$

B
$$6$$

C
$$4$$

D
$$8$$

Solution

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Structure of Atom Test - 23

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Structure of Atom Test - 23

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Question 1

the identity of the element.

the number of neutrons in the atom.

the number of common isotopes of the element.

the atomic radius size.

Solution

Question 2

Earnest Rutherford

Max Planck

Neils Bohr

James Chadwick

J.J. Thompson

Solution

Question 3

$$12$$

$$24$$

$$13$$

$$25$$

Solution

Question 4

$$Mg$$

$$K$$

$$Ar$$

$$Ca$$

Solution

Question 5

Thomson

Rutherford

Bohr

Chadwick

Solution

Question 6

40.8 ev

10.2 ev

51 ev

35 ev

Solution

Question 7

$$r \propto \frac{1}{n}$$

$$r \propto n$$

$$r\propto\frac{1}{n^2}$$

$$r\propto n^2$$

Solution

Question 8

Pauli's exclusion principle

Octet rule

Aufbau principle

Hund's rule

Solution

Question 9

$$10$$

$$9$$

$$19$$

$$28$$

It is impossible to determine from the information given.

Solution

Question 10

$$10$$

$$6$$

$$4$$

$$8$$

Solution

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