The Nucleus

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Notes de leçon

Composition of the Nucleus

The nucleus is composed of protons (positive charge) and neutrons (no charge).
The nucleus has an overall positive charge due to the protons.
Protons and neutrons are collectively called nucleons.
Electrons orbit the nucleus and have a negative charge.

Bohr model of a helium atom

Proton Number (Z) and Nucleon Number (A)

The proton number (Z) is the number of protons in an atom; it determines the element.
The nucleon number (A) is the total number of protons and neutrons in the nucleus.
Number of neutrons = nucleon number − proton number.
In a neutral atom, the number of electrons equals the number of protons.

Nuclide Notation

Nuclide notation is written as ^A_Z X (e.g., ¹⁹⁷₇₉ Au).
The top number A is the nucleon number; the bottom number Z is the proton number.
A nuclide is a group of atoms with the same number of protons and neutrons.

Nuclide notation — lithium-7

Isotopes

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
Isotopes have the same proton number but different nucleon numbers.
Some isotopes are radioactive and emit α, β, or gamma radiation.
Examples: carbon-14, uranium-235, technetium-99m.

Relative Charge of Subatomic Particles

Relative charge compares a particle's charge to the fundamental charge (1.6 × 10⁻¹⁹ C).
Proton: relative charge +1.
Neutron: relative charge 0.
Electron: relative charge −1.

Relative charge of subatomic particles

Nuclear Charge (Extended Tier Only)

Nuclear charge is the total relative charge of the nucleus.
It equals the number of protons multiplied by +1.
For example, a carbon nucleus (6 protons) has a nuclear charge of +6.

Nuclear Fission (Extended Tier Only)

Nuclear fission is the splitting of a large, unstable nucleus into two smaller nuclei.
A neutron collides with the nucleus, causing it to split and release 2–3 neutrons and gamma rays.
The products are daughter nuclei and neutrons with high kinetic energy.
Example: fission of uranium-235.

Nuclear fission process

Nuclear Fusion (Extended Tier Only)

Nuclear fusion is the joining of two light nuclei to form a heavier nucleus.
In stars, hydrogen nuclei fuse to form helium, releasing huge amounts of energy.
Fusion requires extremely high temperature and pressure.
It is difficult to reproduce on Earth.

Nuclear fusion of hydrogen

Diapos

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1.What particles are found in the nucleus of an atom?
Easy
- AProtons and neutrons
- BProtons and electrons
- CNeutrons and electrons
- DProtons, neutrons, and electrons
2.How many neutrons are in a gold atom with mass number 197 and atomic number 79?
Easy
- A130
- B142
- C118
- D106
3.What is the relative charge of a chromium nucleus with 24 protons?
Easy
- A+24
- B+52
- C+1
- D0
4.The number of protons in an atom is equal to the number of electrons.
Easy
True or false?
5.What is the term for atoms of the same element with different numbers of neutrons?
Easy
6.Complete the sentence.
Easy
In nuclide notation, the top number A represents the ____ number.
7.Match each particle to its relative charge.
Easy
- Proton
- Neutron
- Electron
- +1
- 0
- -1
8.Put the following steps of nuclear fission in the correct order.
Medium
- A neutron collides with the nucleus
- The nucleus splits into two smaller nuclei and neutrons
- Gamma rays are emitted
- The nucleus becomes unstable

Plus de questions

9.What is the name of the process where two light nuclei join to form a heavier nucleus?
Easy
10.In the diagram of a sodium atom with electron configuration 2,8,1, what is the total number of electrons?
Easy
- A11
- B12
- C23
- D1
11.In the diagram of a sodium atom, what is the name of the central part labelled with 11 protons and 12 neutrons?
Easy
12.A uranium-235 nucleus undergoes fission. The number of protons in uranium-235 is 92. One of the daughter nuclei has 54 protons. How many protons does the other daughter nucleus have?
Medium
- A34
- B38
- C46
- D42
13.What is the relative charge of a neutron?
Easy
- A+1
- B0
- C-1
- D+2
14.Which two particles are found in the nucleus of an atom?
Easy
- Aprotons and electrons
- Bneutrons and electrons
- Cprotons and neutrons
- Dprotons, neutrons and electrons
15.The number of protons in an atom is called the nucleon number.
Easy
True or false?
16.Atoms of the same element with different numbers of neutrons are called:
Easy
- Aions
- Bisotopes
- Cisomers
- Disotones
17.Nuclear fission is the process where two light nuclei join to form a heavier nucleus.
Easy
True or false?
18.In the nuclide notation 14 6 C, what does the number 14 represent?
Easy
- Athe number of protons
- Bthe number of neutrons
- Cthe nucleon number
- Dthe number of electrons
19.Which statement about an atom with 11 protons and 12 neutrons is correct?
Medium
- AIts nucleon number is 11.
- BIts proton number is 12.
- CIt has 23 electrons.
- DIt is an atom of sodium.
20.A lithium atom has nucleon number 7 and proton number 3. How many neutrons are in the nucleus?
Easy
- A3
- B4
- C7
- D10
21.The nucleus of an atom has an overall positive charge.
Easy
True or false?
22.Which of the following is an example of an isotope?
Easy
- ACarbon-12 and Carbon-14
- BOxygen and ozone
- CSodium ion and sodium atom
- DWater and heavy water
23.Which of the following are products of nuclear fission of uranium-235? (Select all that apply)
Medium
- Atwo smaller nuclei
- Btwo or three neutrons
- Cgamma rays
- Dα particles
- Ea helium nucleus
24.The relative charge of a nucleus with 20 protons is:
Easy
- A+20
- B20
- C0
- D-20
25.Arrange the following events in the order they occur during nuclear fusion in a star.
Medium
- Two hydrogen nuclei approach each other
- Electrostatic repulsion is overcome
- The nuclei fuse to form a helium nucleus
- Energy is released
26.In the diagram of a sodium atom with 11 protons and 12 neutrons, what is the nucleon number?
Easy
- A11
- B12
- C23
- D24
27.Arrange the following events in the correct order for nuclear fission of uranium-235.
Medium
- A neutron is absorbed by the uranium nucleus
- The nucleus splits into two smaller nuclei
- Two or three neutrons are released
- Gamma rays are emitted
28.Which of the following statements about the nucleus of an atom are correct? (Select all that apply)
Medium
- AIt contains protons and neutrons
- BIt has an overall positive charge
- CIt contains electrons
- DIts relative charge is determined by the number of protons
29.The nucleon number of an atom is the total number of protons and neutrons in its nucleus.
Easy
True or false?
30.An atom has 17 protons and 18 neutrons. What is its nucleon number?
Easy
- A17
- B18
- C35
- D1
31.Which of the following statements about nuclear fusion is correct?
Easy
- AIt involves the splitting of a large nucleus into smaller nuclei
- BIt requires extremely high temperatures and pressures
- CIt is the process used in nuclear power stations
- DIt releases neutrons as products
32.A nucleus of uranium-235 absorbs a slow-moving neutron and undergoes fission. One possible pair of daughter nuclei is barium-144 and krypton-90. How many neutrons are released in this fission reaction? (Uranium has atomic number 92, barium 56, krypton 36.)
Medium
- A1
- B2
- C3
- D4
33.The table shows the number of protons and neutrons in four nuclei, W, X, Y and Z. Which nucleus is an isotope of another nucleus in the table?
Medium
- AW and X
- BW and Y
- CX and Z
- DY and Z
34.Which of the following statements about nuclear fusion are correct? (Select all that apply)
Medium
- AIt involves two light nuclei joining to form a heavier nucleus.
- BIt releases a large amount of energy.
- CIt requires extremely high temperatures and pressures.
- DIt is the process used in nuclear power stations on Earth.
35.The nuclide notation for an atom of oxygen is 16 8 O. How many neutrons are in this atom?
Easy
- A8
- B16
- C24
36.An atom of carbon-14 has 6 protons and 8 neutrons.
Easy
True or false?
37.In an experiment to model nuclear fission, a student uses a large plasticine ball to represent a uranium-235 nucleus. She hits it with a smaller ball (neutron) and it splits into two unequal pieces. Which statement best describes the energy change in this model?
Medium
- AThe kinetic energy of the small ball is converted entirely into sound energy.
- BThe small ball provides activation energy to overcome the strong nuclear force, and the pieces fly apart with kinetic energy.
- CThe plasticine ball absorbs the small ball and becomes heavier.
- DThe splitting releases gravitational potential energy.
38.In a nuclear fusion reaction, two light nuclei join to form a heavier nucleus.
Easy
True or false?
39.Which of the following are required for nuclear fusion to occur? Select all that apply.
Easy
- AExtremely high temperature
- BExtremely high pressure
- CA slow-moving neutron
- DA large unstable nucleus
40.Which of the following is an isotope of carbon-12?
Easy
- ACarbon-14
- BNitrogen-14
- COxygen-16
- DCarbon-12 (same)
41.The nucleus of an atom contains protons and neutrons.
Easy
True or false?
42.How many neutrons are in an atom of uranium-235 if its proton number is 92?
Easy
43.Complete the sentence using the words 'proton' and 'neutron'.
Easy
The number of ____ in an atom determines the element, while the number of ____ can vary among isotopes.
44.Name the three subatomic particles: ___, ___, ___.
Easy
The three subatomic particles are ____, ____, and ____.
45.An atom has 26 protons and 30 neutrons. What is its nucleon number?
Easy
46.What is the term for the total number of protons and neutrons in an atom?
Easy
47.Complete the sentence about isotopes.
Easy
Isotopes are atoms of the same ____ with different numbers of ____.
48.How many neutrons are in an atom of carbon-14? (Carbon has atomic number 6.)
Easy
49.What is the term for atoms of the same element that have different numbers of neutrons?
Easy
50.Explain why nuclear fusion is difficult to achieve on Earth.
Hard
51.Describe the process of nuclear fission.
Medium
52.How many neutrons are in an atom of uranium-235 if its proton number is 92?
Easy
- A171
- B143
- C157
- D129
53.An atom has 26 protons and 30 neutrons. What is its nucleon number?
Easy
- A68
- B56
- C62
- D50
54.How many neutrons are in an atom of carbon-14? (Carbon has atomic number 6.)
Easy
- A8
- B9
- C7
- D10

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