Structure of Atom Test

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Structure of Atom Test - 41

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Question 1
1 / -0

An isotope of helium is represented by the symbol $$_{ 2 }^{ 3 }{ He }$$. How many protons, neutrons and electrons are there in an atom of the isotope?

A
$$1$$ proton, $$2$$ neutrons, $$1$$ electron

B
$$1$$ proton, $$3$$ neutrons, $$2$$ electrons

C
$$2$$ protons, $$1$$ neutron, $$2$$ electrons

D
$$2$$ protons, $$3$$ neutrons, $$2$$ electrons

Solution

$$_{ 2 }^{ 3 }He$$ :
Ideal representation of an element : $$_{ Z }^{ A }{ X }$$
Here, $$Z=$$ atomic number $$=$$number of protons
$$A=$$ mass number $$=$$ number of protons $$+$$ number of neutrons
Also, in an atom number of protons $$=$$ number of electrons
So, for $$_{2}^{3}{He}$$ :
Number of protons $$=$$ $$Z=$$ $$2$$
Number of electrons $$=$$ number of protons $$=$$ $$2$$
number of neutrons $$=$$ $$A$$ $$-$$ $$Z$$ $$=$$ $$3$$ $$-$$ $$2$$ $$=$$ $$1$$
Question 2
1 / -0

What is the ratio of the number of neutrons present in potassium and magnesium atoms with mass number $$39$$ and $$24$$ respectively?

A
$$19 : 12$$

B
$$5 : 3$$

C
$$5 : 6$$

D
$$4 : 3$$

Solution

$$(B)$$ $$5 : 3$$

$$Given$$ - Mass number of potassium = $$39$$
Mass number of magnesium = $$24$$

mass number = number of protons + number of neutrons
As we know, number of protons in an element is it's elemental number or atomic number .So,
Potassium has $$19$$ protons and magnesium has $$12$$ protons.
Now,
In potassium,
mass number = no. of protons + no. of neutrons
$$39$$ = $$19$$ + no. of neutrons
number of neutrons = $$39 - 19$$ = $$20$$
In magnesium,
mass number = no. of protons + no. of neutrons
$$24$$ = $$12$$ + no. of neutrons
no. of neutrons = $$24 - 12$$ = $$12$$

Therefore, the ratio of neutrons in $$K$$ and $$Mg$$ is $$20 : 12$$ = $$5 : 3$$.
Question 3
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Analyze the Photoelectron Spectra graph.
What is the electron configuration for this element?

A
$$1s^{2}2s^{1}$$

B
$$1s^{2}2s^{2}$$

C
$$1s^{2}2s^{2}2p^{1}$$

D
$$1s^{2}2s^{2}2p^{2}$$

Solution

There are $$3$$ peaks $$2$$ of these are of equal height having energies $$19.3eV$$ and $$1.36eV$$ representing $$1{ s }^{ 2 }2{ s }^{ 2 }$$ electrons. The third peak is smaller hence it represents $$2{ p }^{ 1 }$$ electron. Thus configuration of the element is $$1{ s }^{ 2 }2{ s }^{ 2 }2{ p }^{ 1 }$$
Question 4
1 / -0

Which of the following statement in relation to the calcium atom is incorrect?

A
$$3s$$ orbital is lower in energy than $$3p$$ orbital

B
$$3p$$ orbital is lower in energy than $$3d$$ orbital

C
$$3s, 3p$$ and $$3d$$ orbitals all have the same energy

D
$$3s, 3p$$ and $$3d$$ orbitals do not have the same energy

Solution

$$3s,3p,3d$$ orbitals don't have same energy.
According to $$(n+l)$$ rule, Order of energy of subshells: $$3s<3p<3d$$
Question 5
1 / -0

Analyze the mass spectrum graph.

Calculate the average atomic mass of the unknown element:

A
$$10.2\ amu$$

B
$$10.5\ amu$$

C
$$10.8\ amu$$

D
$$11.0\ amu$$

Solution

The relative atomic mass
$$ \displaystyle =\dfrac { [ \text { atomic mass of }^{10}X \times \text {abundance of }^{10}X ]+ [ \text { atomic mass of }^{11}X \times \text {abundance of }^{11}X ] }{ \text {abundance of }^{10}X + \text {abundance of }^{11}X } \\ \:=\dfrac { [ \text {10 } \times \text {80.1 } ]+[ \text { 11} \times \text {19.9 } ] }{\text {80.1 } + \text { 19.9} } = \text { 10.2 amu}$$
Question 6
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A student created the following Beer's Law Plot by sampling different concentrations of Copper (II) Sulfate solutions and measuring their absorbance at $$600\ nm$$ on a spectrophotometer.
What does the slope represent?

A
The change in absorbance over time $$\left (\dfrac {\triangle A}{time}\right )$$.

B
The change in concentration over time $$\left (\dfrac {\triangle c}{time}\right )$$.

C
The product of the proportionality constant $$(\epsilon)$$ and the path length $$(b)$$.

D
The product of the absorbance $$(A)$$ and the concentration $$(c)$$.

Solution

Bar's law is absorbance$$=\varepsilon \times concentration \times path$$
Hence, Slope$$=$$product of proportionality constant $$(\varepsilon)$$ and path length $$(b).$$
Question 7
1 / -0

Analyze the Photoelectron Spectra.
What is the identity of the element?

A
$$H$$

B
$$He$$

C
$$Li$$

D
$$Be$$

Solution

There are $$2$$ peaks. The higher peak has energy $$6.26eV$$ representing $$2$$ core $$1s$$ electrons. The smaller peak represent $$1,2s$$ electron. Thus configuration of element is $$1{ s }^{ 2 }2{ s }^{ 1 }$$. Thus the element is $$Li$$.
Question 8
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Statement I: The $$5s$$ orbital is filled after the $$4d$$ orbital
BECAUSE
Statement II: The $$5s$$ orbital has a lower energy than the $$4d$$ orbital

A
Statement $$1$$ and Statement $$2$$ are correct and Statement 2 is the correct explanation of Statement $$1$$

B
Both the Statement $$1$$ and Statement $$2$$ are correct and Statement $$2$$ is NOT the correct explanation of Statement $$1$$

C
Statement $$1$$ is correct but Statement $$2$$ is not correct

D
Statement $$1$$ is not correct but Statement $$2$$ is correct

E
Both the Statement $$1$$ and Statement $$2$$ are not correct

Solution

The $$5s$$ orbital has a lower energy than the $$4d$$ orbital. Lower energy orbitals are filled first. Hence $$5s$$ will be filled before $$4d$$.
Option D is the correct answer.
Question 9
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Scientists previously thought an atom looked like plum pudding. In this model, it was assumed that protons and electrons were distributed throughout the atom almost randomly. Which of the following contributions DISPROVED the Plum Pudding Model?

A
Rutherford's Gold Foil Experiment

B
J.J. Thomson's Cathode Ray Experiment

C
Millikan's Oil Drop Experiment

D
Bohr's Model of the Atom

Solution

In Rutherford's gold foil experiment, few positively charged $$\alpha$$- particles were deflected. The deflection must be due to enormous repulsive force showing that the positive charge of the atom is not spread throughout the atom as Thomson had presumed in his plum-pudding model. The positive charge has to be concentrated in a very small volume that repelled and deflected the positively charged $$\alpha$$-particles.

Thomson's experiment gave the existence of electron and Millikan's oil drop experiment tells about charge of electron.

Bohr's model explained the stability of atom and distribution of electron in orbit.
Thus, option A is correct.
Question 10
1 / -0

Which experiment was developed on the plum pudding model of the atom?

A
Gold foil

B
Cathod ray tube

C
Emission spectra of hydrogen

D
Oil drop

Solution

The plum pudding model of atomic structure was proposed by J.J Thomson in the 19th century.
Thomson discovered that atoms are composite objects, made of pieces with positive and negative charges and the negatively charged electron was very small compared to an entire atom. the gold foil experiment which was concluded was based on this model.

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Structure of Atom Test - 41

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Structure of Atom Test - 41

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Question 1

$$1$$ proton, $$2$$ neutrons, $$1$$ electron

$$1$$ proton, $$3$$ neutrons, $$2$$ electrons

$$2$$ protons, $$1$$ neutron, $$2$$ electrons

$$2$$ protons, $$3$$ neutrons, $$2$$ electrons

Solution

Question 2

$$19 : 12$$

$$5 : 3$$

$$5 : 6$$

$$4 : 3$$

Solution

Question 3

$$1s^{2}2s^{1}$$

$$1s^{2}2s^{2}$$

$$1s^{2}2s^{2}2p^{1}$$

$$1s^{2}2s^{2}2p^{2}$$

Solution

Question 4

$$3s$$ orbital is lower in energy than $$3p$$ orbital

$$3p$$ orbital is lower in energy than $$3d$$ orbital

$$3s, 3p$$ and $$3d$$ orbitals all have the same energy

$$3s, 3p$$ and $$3d$$ orbitals do not have the same energy

Solution

Question 5

$$10.2\ amu$$

$$10.5\ amu$$

$$10.8\ amu$$

$$11.0\ amu$$

Solution

Question 6

The change in absorbance over time $$\left (\dfrac {\triangle A}{time}\right )$$.

The change in concentration over time $$\left (\dfrac {\triangle c}{time}\right )$$.

The product of the proportionality constant $$(\epsilon)$$ and the path length $$(b)$$.

The product of the absorbance $$(A)$$ and the concentration $$(c)$$.

Solution

Question 7

$$H$$

$$He$$

$$Li$$

$$Be$$

Solution

Question 8

Statement $$1$$ and Statement $$2$$ are correct and Statement 2 is the correct explanation of Statement $$1$$

Both the Statement $$1$$ and Statement $$2$$ are correct and Statement $$2$$ is NOT the correct explanation of Statement $$1$$

Statement $$1$$ is correct but Statement $$2$$ is not correct

Statement $$1$$ is not correct but Statement $$2$$ is correct

Both the Statement $$1$$ and Statement $$2$$ are not correct

Solution

Question 9

Rutherford's Gold Foil Experiment

J.J. Thomson's Cathode Ray Experiment

Millikan's Oil Drop Experiment

Bohr's Model of the Atom

Solution

Question 10

Gold foil

Cathod ray tube

Emission spectra of hydrogen

Oil drop

Solution

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