Nuclear Model of the Atom

Chapter 25 MCQs

Nuclear Model of the Atom

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

1

Which statement best describes the nuclear model of the atom?

A electrons and protons are spread evenly throughout the atom
B the atom has a tiny dense positive nucleus with electrons around it
C the atom is a solid sphere with no empty space
D neutrons orbit the nucleus like electrons

2

Which particles are found inside the nucleus?

A protons and electrons
B neutrons and electrons
C protons and neutrons
D protons, neutrons and electrons

3

Which particle has a negative charge?

A proton
B neutron
C electron
D nucleon

4

Which particle has no electric charge?

A proton
B neutron
C electron
D beta particle only

5

Which particle has the smallest mass?

A proton
B neutron
C electron
D alpha particle

6

A neutral atom contains 19 protons.

How many electrons does it contain?

A 0
B 19
C 38
D cannot be determined without knowing neutrons

7

A neutral atom contains 12 electrons and 14 neutrons.

What is its proton number?

A 12
B 14
C 26
D 2

8

An atom has 15 protons, 16 neutrons and 15 electrons.

What are its proton number and nucleon number?

	proton number	nucleon number
A	15	16
B	15	31
C	16	31
D	31	15

9

An atom has nucleon number 40 and proton number 18.

How many neutrons are in its nucleus?

A 18
B 22
C 40
D 58

10

A nucleus is represented as:

⁶⁵₂₉X

How many neutrons are in the nucleus?

A 29
B 36
C 65
D 94

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

11

A neutral atom is represented as:

²³₁₁Na

How many protons, neutrons and electrons does it contain?

	protons	neutrons	electrons
A	11	12	11
B	12	11	12
C	23	11	23
D	11	23	11

12

A neutral atom has 30 protons and 34 neutrons.

Which symbol represents the atom?

A ³⁴₃₀X
B ⁶⁴₃₀X
C ⁶⁴₃₄X
D ³⁰₆₄X

13

An ion has 13 protons, 14 neutrons and 10 electrons.

What is the charge on the ion?

A 3−
B 1−
C 1+
D 3+

14

An ion has 8 protons, 10 neutrons and 10 electrons.

Which statement is correct?

A it has charge 2+ and nucleon number 18
B it has charge 2− and nucleon number 18
C it has charge 2− and nucleon number 28
D it has charge 2+ and nucleon number 28

15

A neutral atom becomes a positive ion.

What has happened?

A it gained electrons
B it lost electrons
C it gained neutrons
D it lost protons

16

A neutral atom becomes a negative ion.

What has happened?

A it gained electrons
B it lost electrons
C it gained protons
D it lost neutrons

17

Which statement about proton number is correct?

A it is the number of protons plus neutrons
B it is the number of neutrons only
C it identifies the element
D it changes when an atom gains electrons

18

Which statement about nucleon number is correct?

A it is the number of protons plus neutrons
B it is the number of electrons only
C it is the number of protons minus neutrons
D it is always equal to the number of electrons

19

Which pair of atoms are isotopes of the same element?

A ³⁵₁₇X and ³⁷₁₇X
B ³⁵₁₇X and ³⁵₁₈Y
C ³⁷₁₇X and ³⁷₁₈Y
D ³⁵₁₇X and ³⁶₁₈Y

20

Which statement about isotopes is correct?

A isotopes have the same number of neutrons but different proton numbers
B isotopes have the same proton number but different numbers of neutrons
C isotopes have different proton numbers and different electron charges only
D isotopes have the same nucleon number but different proton numbers

21

Two atoms have the same proton number but different nucleon numbers.

What must be true?

A they are isotopes of the same element
B they are ions of different elements
C they have the same number of neutrons
D they have different numbers of protons

22

Two neutral atoms are isotopes of the same element.

Which quantities are the same?

A number of protons and number of electrons
B number of neutrons and number of electrons
C nucleon number and number of neutrons
D number of protons and number of neutrons

23

Two isotopes of chlorine are ³⁵₁₇Cl and ³⁷₁₇Cl.

Which row is correct?

	protons	electrons in neutral atom	neutrons
A	same	same	different
B	same	different	same
C	different	same	same
D	different	different	same

24

An isotope has 6 protons and 8 neutrons.

Which symbol represents it?

A ⁸₆X
B ¹⁴₆X
C ¹⁴₈X
D ⁶₁₄X

25

A nucleus has nucleon number 238 and contains 146 neutrons.

What is its proton number?

A 92
B 146
C 238
D 384

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

26

The plum pudding model of the atom suggested that:

A electrons orbit a tiny nucleus
B positive charge is spread throughout the atom with electrons embedded in it
C neutrons form rings around electrons
D the atom contains only empty space

27

Rutherford’s alpha-particle scattering experiment involved firing alpha particles at:

A a thick block of lead
B a thin sheet of gold foil
C a charged plastic rod
D a radioactive gas only

28

In Rutherford’s alpha-particle scattering experiment, most alpha particles passed straight through the foil.

What did this suggest?

A atoms are mostly empty space
B atoms are completely solid
C nuclei are negatively charged
D electrons have the same mass as protons

29

In Rutherford’s experiment, a few alpha particles were deflected through large angles.

What did this suggest?

A the atom contains a small dense positively charged nucleus
B electrons are heavier than alpha particles
C the atom has no nucleus
D positive charge is spread evenly through the atom

30

Why were only a small number of alpha particles deflected through large angles?

A the nucleus occupies a very small fraction of the atom’s volume
B the atom is made mostly of solid positive matter
C alpha particles have no charge
D electrons strongly repel alpha particles

31

Why are alpha particles repelled by the nucleus?

A both alpha particles and the nucleus are positively charged
B both alpha particles and the nucleus are negatively charged
C alpha particles have no charge but the nucleus is positive
D the nucleus is made of electrons

32

An alpha particle passes close to a nucleus and is deflected.

Which factor would usually cause a larger deflection?

A passing closer to the nucleus
B passing farther from the nucleus
C reducing the charge of the nucleus to zero
D removing all protons from the nucleus

33

Which observation from alpha scattering gives the strongest evidence for a concentrated positive nucleus?

A most alpha particles pass straight through
B some alpha particles are strongly deflected or rebound
C the gold foil becomes hot
D electrons leave the foil and form sparks

34

The nuclear model replaced the plum pudding model mainly because:

A alpha-particle scattering results could not be explained by spread-out positive charge
B electrons were found to be made of protons
C atoms were found to have no mass
D gold atoms were found to be radioactive

35

Which statement is correct about the size of the nucleus compared with the size of the atom?

A the nucleus is almost the same size as the atom
B the nucleus is much smaller than the atom
C the nucleus is larger than the atom
D the nucleus fills all the empty space in the atom

36

Which statement is correct about the mass of an atom?

A most of the mass is in the electrons
B most of the mass is in the nucleus
C mass is spread evenly throughout the atom
D electrons have the same mass as neutrons

37

Which statement is correct about the charge of an atomic nucleus?

A it is negative because it contains electrons
B it is positive because it contains protons
C it is neutral because protons and electrons cancel inside it
D it changes from positive to negative every second

38

A nucleus contains 9 protons and 10 neutrons.

Which statement is correct?

A its charge is +9e and its nucleon number is 19
B its charge is +10e and its nucleon number is 19
C its charge is −9e and its nucleon number is 19
D its charge is +19e and its nucleon number is 9

39

A neutral atom has 20 protons and 22 neutrons.

Which row is correct?

	nuclear charge	number of electrons
A	+20e	20
B	+22e	20
C	+42e	22
D	−20e	20

40

A nucleus has charge +3.2 × 10⁻¹⁸ C.

Charge on one proton = 1.6 × 10⁻¹⁹ C.

How many protons are in the nucleus?

A 2
B 20
C 32
D 200

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

41

A neutral atom has 18 electrons and nucleon number 40.

How many neutrons does it contain?

A 18
B 22
C 40
D 58

42

An atom has proton number Z and nucleon number A.

Which expression gives the number of neutrons?

A A + Z
B A − Z
C Z − A
D A ÷ Z

43

An atom has 12 protons and 12 neutrons. It loses two electrons.

Which statement is correct?

A it becomes an ion with charge 2+ and nucleon number 24
B it becomes an ion with charge 2− and nucleon number 24
C it becomes an isotope with nucleon number 22
D it becomes a different element with proton number 10

44

An atom has 16 protons, 18 neutrons and 18 electrons.

Which statement is correct?

A it is a neutral atom with nucleon number 34
B it is a 2− ion with nucleon number 34
C it is a 2+ ion with nucleon number 34
D it is a 2− ion with nucleon number 52

45

A neutral atom X has nucleon number 31 and proton number 15.

A neutral atom Y has nucleon number 32 and proton number 16.

Which statement is correct?

A X and Y are isotopes of the same element
B X and Y are different elements
C X and Y have the same number of protons
D X and Y have the same number of electrons

46

Which change would produce an isotope of an atom without changing the element?

A add one neutron to the nucleus
B add one proton to the nucleus
C remove one proton from the nucleus
D remove one electron from outside the nucleus

47

Which change would produce an ion of an atom without changing its nucleus?

A remove an electron
B add a neutron
C remove a proton
D split the nucleus

48

A neutral atom of ⁴⁰₂₀Ca loses two electrons to form an ion.

Which row describes the ion?

	protons	neutrons	electrons	charge
A	20	20	18	2+
B	20	20	22	2−
C	18	22	18	2+
D	20	40	18	2+

49

Which statement best explains why the atom is electrically neutral overall?

A number of neutrons equals number of electrons
B total positive charge of protons equals total negative charge of electrons
C protons and neutrons have equal and opposite charges
D electrons are inside the nucleus with protons

50

Which statement is correct about the nuclear model of the atom?

A electrons are inside the nucleus with protons and neutrons
B the nucleus contains most of the atom’s mass but occupies very little of its volume
C the nucleus has negative charge and large volume
D protons orbit the nucleus while electrons stay fixed

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Chapter 25 Answer Key

Nuclear Model of the Atom

Q	Ans	Q	Ans	Q	Ans	Q	Ans	Q	Ans
1	B	11	A	21	A	31	A	41	B
2	C	12	B	22	A	32	A	42	B
3	C	13	D	23	A	33	B	43	A
4	B	14	B	24	B	34	A	44	B
5	C	15	B	25	A	35	B	45	B
6	B	16	A	26	B	36	B	46	A
7	A	17	C	27	B	37	B	47	A
8	B	18	A	28	A	38	A	48	A
9	B	19	A	29	A	39	A	49	B
10	B	20	B	30	A	40	B	50	B

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Detailed Explanations

1. B

The nuclear model says:
- atom has a tiny dense nucleus
- nucleus is positively charged
- electrons are around the nucleus
- most of the atom is empty space
The plum pudding model had charge spread throughout the atom, which Rutherford’s experiment destroyed like a bad argument.

2. C

The nucleus contains:
- protons
- neutrons
Electrons are outside the nucleus.

3. C

Electron has negative charge.
Proton has positive charge.
Neutron has no charge.

4. B

Neutron has no electric charge.
That is why it is called neutral.
Proton is positive.
Electron is negative.

5. C

Electron has the smallest mass.
Proton and neutron have much larger masses.
Alpha particle is a helium nucleus, so it is much heavier than an electron.

6. B

A neutral atom has:
- number of protons = number of electrons
If it has 19 protons, it has 19 electrons.

7. A

Neutral atom:
- electrons = protons
It has 12 electrons, so it has 12 protons.
Proton number = 12

8. B

Proton number = number of protons = 15
Nucleon number = protons + neutrons
Nucleon number = 15 + 16 = 31

9. B

Neutrons = nucleon number − proton number
Neutrons = 40 − 18
Neutrons = 22

10. B

In ⁶⁵₂₉X:
- nucleon number = 65
- proton number = 29
Neutrons = 65 − 29
Neutrons = 36

11. A

In ²³₁₁Na:
- protons = 11
- nucleon number = 23
- neutrons = 23 − 11 = 12
Neutral atom:
- electrons = protons = 11
Answer = 11 protons, 12 neutrons, 11 electrons

12. B

Protons = 30, so proton number = 30.
Neutrons = 34.
Nucleon number = 30 + 34 = 64.
Symbol = ⁶⁴₃₀X

13. D

Protons = 13.
Electrons = 10.
Net charge = +13 − 10 = +3.
Ion charge = 3+

14. B

Protons = 8.
Electrons = 10.
Extra 2 electrons means charge = 2−
Nucleon number = protons + neutrons
Nucleon number = 8 + 10 = 18

15. B

A positive ion forms when an atom loses electrons.
Losing negative charge leaves the atom positive.
Protons do not leave during normal ion formation.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

16. A

A negative ion forms when an atom gains electrons.
Extra electrons give the atom negative charge.

17. C

Proton number is the number of protons.
It identifies the element.
If proton number changes, the element changes.
Gaining or losing electrons changes charge, not element.

18. A

Nucleon number = protons + neutrons.
Nucleons are the particles in the nucleus:
- protons
- neutrons

19. A

Isotopes have:
- same proton number
- different nucleon number
³⁵₁₇X and ³⁷₁₇X both have proton number 17.
Their nucleon numbers are different.
So they are isotopes.

20. B

Isotopes are atoms of the same element with different numbers of neutrons.
Same element means same proton number.
Different neutrons means different nucleon numbers.

21. A

Same proton number means same element.
Different nucleon number means different number of neutrons.
Therefore they are isotopes of the same element.

22. A

Neutral isotopes of the same element have:
- same number of protons
- same number of electrons
- different number of neutrons
Same proton number gives same element.
Neutral atoms have electrons equal to protons.

23. A

³⁵₁₇Cl and ³⁷₁₇Cl:
- both have 17 protons
- neutral atoms both have 17 electrons
- neutrons differ
³⁵Cl has 35 − 17 = 18 neutrons.
³⁷Cl has 37 − 17 = 20 neutrons.

24. B

Protons = 6, so proton number = 6.
Neutrons = 8.
Nucleon number = 6 + 8 = 14.
Symbol = ¹⁴₆X

25. A

Nucleon number = protons + neutrons.
Proton number = nucleon number − neutrons.
Proton number = 238 − 146.
Proton number = 92

26. B

Plum pudding model:
- positive charge spread throughout the atom
- electrons embedded in the positive charge
It did not include a tiny dense nucleus.

27. B

Rutherford’s experiment fired alpha particles at thin gold foil.
Gold foil was used because it could be made extremely thin.
The alpha particles were detected after passing through or being deflected.

28. A

Most alpha particles passed straight through.
This showed that most of the atom is empty space.
If atoms were solid, most alpha particles would have bounced back or been strongly deflected.

29. A

A few alpha particles were deflected through large angles.
Some even rebounded.
This showed the atom has a tiny, dense, positively charged nucleus.

30. A

Only a few alpha particles came close enough to the nucleus to be strongly deflected.
This means the nucleus is extremely small compared with the atom.
Most alpha particles pass through empty space.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

31. A

Alpha particles are positively charged.
The nucleus is positively charged because it contains protons.
Like charges repel.
Therefore alpha particles are repelled by the nucleus.

32. A

The closer an alpha particle passes to the nucleus, the stronger the repulsive force.
Stronger force causes greater deflection.
Passing far away causes little or no deflection.

33. B

Strong deflection or rebound gives the strongest evidence for a concentrated positive nucleus.
A spread-out positive charge could not repel alpha particles backwards strongly.
This was the killer evidence against the plum pudding model.

34. A

The plum pudding model could not explain large-angle alpha deflections.
The nuclear model could explain them using a tiny dense positive nucleus.
So Rutherford’s results replaced the old model.

35. B

The nucleus is much smaller than the atom.
The atom is mostly empty space.
The nucleus occupies a tiny fraction of the atom’s volume.

36. B

Most of the atom’s mass is in the nucleus.
Protons and neutrons are much heavier than electrons.
Electrons contribute very little to the total mass.

37. B

The nucleus is positive because it contains protons.
Neutrons are neutral.
Electrons are not inside the nucleus in the basic nuclear model.

38. A

Nucleus has 9 protons and 10 neutrons.
Nuclear charge = +9e.
Nucleon number = protons + neutrons
Nucleon number = 9 + 10 = 19

39. A

Nuclear charge depends on protons.
20 protons means nuclear charge = +20e
Neutral atom has electrons = protons = 20

40. B

Nuclear charge = number of protons × charge of one proton.
Number of protons = 3.2 × 10⁻¹⁸ / 1.6 × 10⁻¹⁹
Number of protons = 20
Answer = 20

41. B

Neutral atom has 18 electrons.
Therefore it has 18 protons.
Nucleon number = 40.
Neutrons = 40 − 18.
Neutrons = 22

42. B

Nucleon number = A.
Proton number = Z.
Neutrons = nucleon number − proton number.
Neutrons = A − Z

43. A

Protons = 12.
Neutrons = 12.
Nucleon number = 24.
Losing two electrons makes charge = 2+
Nucleus does not change, so nucleon number stays 24.

44. B

Protons = 16.
Neutrons = 18.
Electrons = 18.
It has 2 more electrons than protons, so charge = 2−
Nucleon number = 16 + 18 = 34

45. B

X has proton number 15.
Y has proton number 16.
Different proton numbers mean different elements.
They are not isotopes because isotopes must have the same proton number.

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

46. A

Adding a neutron changes the nucleon number.
Proton number stays the same.
Same proton number means same element.
Different neutron number means isotope.

47. A

An ion forms when electrons are gained or lost.
Removing an electron makes a positive ion.
The nucleus remains unchanged.

48. A

⁴⁰₂₀Ca:
- protons = 20
- neutrons = 40 − 20 = 20
Neutral calcium has 20 electrons.
Losing two electrons gives 18 electrons and charge 2+.
Correct row = 20 protons, 20 neutrons, 18 electrons, 2+

49. B

A neutral atom has no overall charge.
This is because:
- total positive charge of protons = total negative charge of electrons
Neutrons do not affect charge.

50. B

In the nuclear model:
- nucleus contains most of the atom’s mass
- nucleus is tiny compared with the atom
- electrons are outside the nucleus
- most of the atom is empty space

For Full Scale Course: Written and Compiled By Sir Hunain Zia (AYLOTI), World Record Holder With 154 Total Personal A Grades, 11 World Records and 7 Distinctions, Educate A Change.

Common Traps From This Chapter

Trap	Correct Rule
Proton number	number of protons
Nucleon number	protons + neutrons
Neutrons	nucleon number − proton number
Neutral atom	protons = electrons
Positive ion	lost electrons
Negative ion	gained electrons
Isotopes	same protons, different neutrons
Same element	same proton number
Different proton number	different element
Nucleus contains	protons and neutrons
Electrons	outside nucleus
Nuclear charge	positive, due to protons
Most atomic mass	in nucleus
Most atomic volume	empty space
Plum pudding model	positive charge spread out with electrons embedded
Rutherford experiment	alpha particles fired at thin gold foil
Most alpha particles pass through	atom mostly empty space
Large deflections/rebounds	tiny dense positive nucleus
Alpha particle	positive, repelled by nucleus
Closer alpha path to nucleus	greater deflection
Adding neutron	makes isotope
Removing electron	makes positive ion
Adding proton	changes element

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