The nucleus
16 flashcards to master The nucleus
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Describe the composition of the nucleus of an atom.
The nucleus of an atom is composed of protons and neutrons. Protons are positively charged particles, and neutrons are neutral particles. These two types of particles are collectively known as nucleons.
State the two types of particles found within the nucleus of an atom and give the relative charge of each.
The nucleus contains protons, which have a relative charge of +1, and neutrons, which have a relative charge of 0 (neutral).
State the relative charge of a proton, a neutron, and an electron.
Proton: +1
Neutron: 0
Electron: -1
Explanation: These are the standard relative charges assigned to these subatomic particles. The actual charge of a proton is +1.6 x 10⁻¹⁹ C, and the charge of an electron is -1.6 x 10⁻¹⁹ C. Neutrons have no charge.
A neutral atom of sodium (Na) contains 11 protons, 12 neutrons, and 11 electrons. Explain why the atom is electrically neutral, referencing the relative charges of the subatomic particles.
The atom is electrically neutral because the total positive charge of the protons cancels out the total negative charge of the electrons.
Protons: 11 protons * (+1 charge/proton) = +11
Electrons: 11 electrons * (-1 charge/electron) = -11
Neutrons: Neutrons have 0 charge.
Total charge: +11 + (-11) + 0 = 0
Define the term proton number (atomic number) Z.
The proton number (Z) is the number of protons in the nucleus of an atom. This number determines the element that the atom is.
An atom of Uranium-235 (<sup>235</sup>U) has a proton number of 92. State the number of neutrons in the nucleus of this atom.
Number of neutrons = Nucleon number (A) - Proton number (Z)
Number of neutrons = 235 - 92 = 143
Answer: 143 neutrons. This calculation uses the definition that the nucleon number represents the total number of protons and neutrons in the nucleus.
A nucleus is represented by the nuclide notation 235/92 U. State the number of protons and neutrons in this nucleus.
Number of protons = Z = 92.
Number of neutrons = A - Z = 235 - 92 = 143.
Protons determine the element, and neutrons affect stability.
The nuclide notation for a nucleus is given as A/ZX. Explain what the numbers A and Z represent.
A represents the nucleon number (mass number), which is the total number of protons and neutrons in the nucleus.
Z represents the proton number (atomic number), which is the number of protons in the nucleus. The number of protons identifies the element.
Explain what is meant by the term 'isotope'.
Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. This means they have the same atomic number but different mass numbers. Explanation: The number of protons defines the element, but the number of neutrons can vary.
State two isotopes of Hydrogen. Hydrogen has an atomic number of 1.
1. Hydrogen-1 (Protium): 1 proton, 0 neutrons
2. Hydrogen-2 (Deuterium): 1 proton, 1 neutron
Explanation: Isotopes of the same element (Hydrogen) have the same number of protons (1) but differ in the number of neutrons (0 and 1 respectively).
Describe the process of nuclear fission, including what happens to the mass and energy of the system.
Nuclear fission is the splitting of a heavy nucleus into two smaller nuclei. The total mass of the products is slightly less than the mass of the original nucleus, and this 'missing' mass is converted into energy (E=mc²) according to Einstein's mass-energy equivalence. Therefore, mass decreases and energy increases during fission.
State two differences between nuclear fission and nuclear fusion.
1. Fission is the splitting of a large nucleus, while fusion is the joining of two small nuclei.
2. Fission reactions are commonly used in nuclear power plants, while fusion reactions occur in stars and are difficult to achieve on Earth.
The nucleus of an atom has a proton number of 11. State the relative charge on the nucleus.
The relative charge on the nucleus is +11.
Explanation: The relative charge on the nucleus is equal to the proton number, as each proton has a charge of +1 and neutrons are neutral.
Explain why the relative charge of a nucleus is equal to its proton number and not its nucleon number.
The relative charge of a nucleus is determined by the number of protons it contains. Each proton has a relative charge of +1. Neutrons, which are also present in the nucleus and contribute to the nucleon number, are electrically neutral (have no charge). Therefore, they do not affect the overall charge of the nucleus.
A nucleus has a nucleon number of 235. The relative mass of a single nucleon is approximately 1 atomic mass unit (u). Calculate the approximate relative mass of the nucleus.
Relative mass = Nucleon number × mass of a single nucleon
Relative mass = 235 × 1 u
Relative mass = 235 u
Explanation: The nucleon number represents the total number of protons and neutrons in the nucleus. Since each nucleon has a relative mass of approximately 1 u, the relative mass of the nucleus is simply the nucleon number multiplied by 1 u.
State the relationship between the nucleon number of a nucleus and its relative mass.
The relative mass of a nucleus is approximately equal to its nucleon number, when expressed in atomic mass units (u). This is because each nucleon (proton or neutron) contributes approximately 1 atomic mass unit to the total mass of the nucleus.
Key Questions: The nucleus
State the relative charge of a proton, a neutron, and an electron.
Proton: +1
Neutron: 0
Electron: -1
Explanation: These are the standard relative charges assigned to these subatomic particles. The actual charge of a proton is +1.6 x 10⁻¹⁹ C, and the charge of an electron is -1.6 x 10⁻¹⁹ C. Neutrons have no charge.
Define the term proton number (atomic number) Z.
The proton number (Z) is the number of protons in the nucleus of an atom. This number determines the element that the atom is.
About The nucleus (5.1.2)
These 16 flashcards cover everything you need to know about The nucleus for your Cambridge IGCSE Physics (0625) exam. Each card is designed based on the official syllabus requirements.
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After mastering The nucleus, explore these related topics:
- 5.1.1 The atom - 6 flashcards
- 5.2.1 Detection of radioactivity - 10 flashcards
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