The Nuclear Model Of The Atom

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Notas de aula

Atomic Structure

Atoms consist of a small, dense, positively charged nucleus surrounded by negatively charged electrons in orbit.
Atom radius ≈ 1 × 10⁻¹⁰ m; nucleus radius is over 10,000 times smaller but contains almost all the mass.
A neutral atom has equal numbers of protons and electrons.
Ions are formed when an atom loses or gains electrons: losing electrons → positive ion; gaining electrons → negative ion.

Diagram of an atom with a positively charged nucleus and negatively charged electrons orbiting it.

Rutherford's Alpha Scattering Experiment (Extended Tier)

In 1909, Rutherford, Geiger and Marsden fired α-particles at thin gold foil.
Most α-particles passed straight through → atom is mostly empty space.
Some were deflected → repelled by a small, positively charged nucleus.
A very few bounced back → nucleus is tiny and contains most of the mass.
This disproved the Plum Pudding model and provided evidence for the nuclear model.

Rutherford's Alpha Scattering Experiment

The Nucleus

The nucleus contains protons (positive charge) and neutrons (no charge); overall positive charge.
Proton number (Z) = number of protons = atomic number; determines the element.
Nucleon number (A) = total number of protons and neutrons (mass number).
Number of neutrons = nucleon number − proton number.

Structure of the atom

Nuclide Notation

Nuclide notation: \ce{^A_ZX} where X = element symbol, A = nucleon number, Z = proton number.
Example: \ce{¹⁹⁷₇₉Au} has 79 protons, 118 neutrons (197−79), and 79 electrons.
A nuclide is a group of atoms with the same number of protons and neutrons.

Nuclide notation

Isotopes

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.
They have the same Z but different A.
Example: \ce{²³⁵₉₂U} and \ce{²³⁸₉₂U} are isotopes of uranium.
Isotopes tend to be more unstable due to imbalance of protons and neutrons.

Isotopes of hydrogen

Protons, Neutrons & Electrons

Relative charges: proton = +1, neutron = 0, electron = −1.
Relative masses: proton = 1, neutron = 1, electron = negligible (≈1/2000).
Nuclear charge = number of protons × (+1).
Relative mass of atom ≈ nucleon number (mass of electrons negligible).

Nuclear Fission (Extended Tier)

Nuclear fission is the splitting of a large, unstable nucleus into two smaller nuclei.
A neutron collides with the nucleus, which splits into daughter nuclei and 2–3 neutrons, releasing energy and gamma rays.
Example: \ce{²³⁵₉₂U + ¹₀n → ⁹²₃₆Kr + ¹⁴¹₅₆Ba + 3¹₀n + energy}.
The total nucleon and proton numbers are conserved; mass decreases slightly as mass is converted to energy.
Used in nuclear power stations with fuels like uranium-235 and plutonium.

Diagram illustrating nuclear fission where a neutron collides with a target nucleus, splitting it into fission products and releasing more neutrons.

Nuclear Fusion (Extended Tier)

Nuclear fusion is the joining of two light nuclei to form a heavier nucleus.
Occurs in stars (e.g., hydrogen fusing to helium) and requires extremely high temperature and pressure.
Example: \ce{²₁H + ¹₁H → ³₂He + energy}.
Mass of product is slightly less than reactants; mass converted to energy releases huge amounts (1 kg hydrogen ≈ 10 million kg coal).

Nuclear fusion of hydrogen

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Questões de prática

Prévia grátis — 8 de 50 perguntas. Cadastre-se para ver todas.

1.Which statement about the three isotopes of hydrogen is correct?
Easy
- AThey must have different numbers of electrons orbiting their nucleus.
- BThey must all have one proton in their nuclei.
- CThey must all have one neutron in their nuclei.
- DThey must all have the same number of nucleons in their nucleus.
2.An atom consists of electrons orbiting a nucleus. The nucleus contains protons and neutrons. For the atom to be neutral, which statement must be correct?
Easy
- AThe number of electrons is equal to the number of protons.
- BThe number of protons is equal to the number of neutrons.
- CThe number of electrons, protons and neutrons are all different.
- DThe number of electrons is equal to the number of neutrons.
3.The charge on an electron is -e. Which answer correctly describes the charge of a proton and the charge on a neutron?
Easy
- AProton: 0, Neutron: +e
- BProton: +e, Neutron: -e
- CProton: +e, Neutron: 0
- DProton: -e, Neutron: +e
4.An isotope of uranium is represented by the symbol 92²³⁵U. Which of the answers below could be a different isotope of uranium?
Medium
- A91²³⁵U
- B92²³⁸U
- C235⁹²U
- D90²³⁵U
5.Atom X loses an electron to form an ion. Atom Y gains an electron to form an ion. Which row in the table is correct?
Easy
- Acharge on ion of X: positive, charge on ion of Y: positive
- Bcharge on ion of X: positive, charge on ion of Y: negative
- Ccharge on ion of X: negative, charge on ion of Y: positive
- Dcharge on ion of X: negative, charge on ion of Y: negative
6.Where is the positive charge in an atom?
Easy
- Aon the orbiting particles
- Bin the nucleus
- Cin the space between the nucleus and the orbiting particles
- Dspread throughout the atom
7.Which row correctly identifies the relative charges of the three types of particle in an atom?
Easy
- Aproton: +1, neutron: -1, electron: 0
- Bproton: +1, neutron: 0, electron: -1
- Cproton: -1, neutron: +1, electron: 0
- Dproton: -1, neutron: 0, electron: +1
8.How many neutrons are in a nucleus of aluminium? The chemical symbol is 13²⁷Al.
Easy
- A13
- B27
- C14
- D40

Mais perguntas

9.Which of the following statements would not be correct for the nucleus of any atom?
Medium
- AThe nucleus contains protons and neutrons.
- BThe nucleus has a total charge of zero.
- CThe nucleus is very small compared to the size of the atom.
- DThe atom contains the same number of protons and electrons.
10.A nitrogen atom loses an electron. What is it called now?
Easy
- AAn atom
- BAn isotope
- CA negative ion
- DA positive ion
11.Which row in the table describes the process of nuclear fusion and identifies the change in total mass of the particles involved?
Medium
- Aprocess: a large nucleus splits into two smaller nuclei, change in total mass: decreases
- Bprocess: a large nucleus splits into two smaller nuclei, change in total mass: increases
- Cprocess: two small nuclei combine to form a larger nucleus, change in total mass: decreases
- Dprocess: two small nuclei combine to form a larger nucleus, change in total mass: increases
12.The diagram shows the nuclide notation for an atom. What is the number of neutrons in this atom?
Easy
- A6
- B12
- C18
- D0
13.The diagram shows a model of a lithium atom. The nucleus contains 3 protons and 4 neutrons. How many electrons are in the atom?
Easy
- A3
- B4
- C7
- D1
14.The diagram shows a model of a sodium atom. The nucleus contains 11 protons and 12 neutrons. Which shell contains the most electrons?
Medium
- AFirst shell
- BSecond shell
- CThird shell
- DAll shells have the same number
15.In Rutherford's α scattering experiment, a beam of α particles is directed at a thin gold foil. Which statement explains why most α particles pass straight through the foil?
Medium
- AThe α particles are very small and miss the gold atoms entirely.
- BThe gold atoms are mostly empty space.
- CThe α particles are repelled by the nucleus and go around it.
- DThe α particles are neutral and not affected by the gold atoms.
16.In Rutherford's α scattering experiment, a few α particles are deflected back towards the source. What does this observation indicate about the nucleus?
Medium
- AThe nucleus is very small and positively charged.
- BThe nucleus is large and negatively charged.
- CThe nucleus is the same size as the atom.
- DThe nucleus has no charge.
17.The nuclide notation for an atom is 17³⁵Cl. How many neutrons are in this atom?
Easy
- A17
- B18
- C35
- D52
18.Which of the following pairs are isotopes of the same element?
Medium
- A19⁴⁰K and 20⁴⁰Ca
- B6¹²C and 6¹⁴C
- C8¹⁶O and 7¹⁵N
- D1¹H and 2³He
19.A nuclide equation for fission is: 92²³⁵U + 0¹n → 36⁹²Kr + 56¹⁴¹Ba + N 0¹n. What is the value of N?
Medium
- A2
- B3
- C4
- D1
20.The relative charge of a proton is +1 and the relative charge of an electron is -1. What is the relative charge of the nucleus of an atom of beryllium (proton number 4)?
Medium
- A+4
- B-4
- C0
- D+1
21.Which of the following statements about nuclear fusion is correct?
Medium
- AFusion involves the splitting of a large nucleus into two smaller nuclei.
- BFusion occurs in nuclear power stations on Earth.
- CFusion involves two light nuclei joining to form a heavier nucleus.
- DFusion releases less energy than fission.
22.An atom has 8 protons and 10 neutrons. What is its nucleon number?
Easy
- A8
- B10
- C18
- D2
23.A neutral atom of an element has 19 electrons. The nucleon number of this atom is 39. How many neutrons does it have?
Medium
- A19
- B20
- C39
- D58
24.Which of the following best describes the composition of the nucleus of an atom?
Easy
- AProtons and electrons
- BNeutrons and electrons
- CProtons and neutrons
- DProtons, neutrons, and electrons
25.In Rutherford's α scattering experiment, most α particles passed straight through the gold foil. What does this observation suggest about the structure of the atom?
Medium
- AThe atom is mostly empty space.
- BThe nucleus is very small and dense.
- CThe nucleus is positively charged.
- DElectrons are arranged in shells.
26.The diagram shows a model of a sodium atom with 11 protons and 12 neutrons. How many electrons are in a neutral atom of sodium?
Easy
- A11
- B12
- C23
- D1
27.In Rutherford's α scattering experiment, a few α particles were deflected back towards the source. Which conclusion about the nucleus is supported by this observation?
Medium
- AThe nucleus is very small and contains most of the mass of the atom.
- BThe nucleus is positively charged.
- CThe atom is mostly empty space.
- DElectrons orbit the nucleus in fixed paths.
28.What is the relative charge of a neutron?
Easy
- A0
- B+1
- C-1
- D+2
29.The nuclide notation for an atom is 6¹²C. How many neutrons are in this atom?
Easy
- A6
- B12
- C18
- D0
30.Which particle in an atom has a negative charge?
Easy
- AElectron
- BProton
- CNeutron
- DNucleus
31.In a nuclear fission reaction, the total mass of the products is slightly less than the total mass of the original nucleus and neutron. What happens to the 'missing' mass?
Medium
- AIt is converted into energy according to E=mc².
- BIt is destroyed.
- CIt is converted into additional neutrons.
- DIt remains as mass but is undetectable.
32.Which of the following is a correct statement about the isotopes of an element?
Easy
- AIsotopes have the same number of protons but different numbers of neutrons.
- BIsotopes have the same number of neutrons but different numbers of protons.
- CIsotopes have the same number of nucleons but different numbers of protons.
- DIsotopes have different chemical properties.
33.The nuclide notation for a generic element is Z^A X. Which row correctly identifies the terms X, A, and Z?
Easy
- AX = symbol, A = nucleon number, Z = proton number
- BX = symbol, A = proton number, Z = nucleon number
- CX = symbol, A = neutron number, Z = proton number
- DX = nucleon number, A = proton number, Z = symbol
34.Which statement about the nucleus of any atom is correct?
Easy
- AThe nucleus contains protons and neutrons.
- BThe nucleus has a total charge of zero.
- CThe nucleus is very large compared to the size of the atom.
- DThe nucleus contains the same number of protons and electrons.
35.In the nuclide notation 79¹⁹⁷ Au, how many neutrons are in the nucleus?
Easy
- A118
- B79
- C197
- D276
36.Which subatomic particle has a relative charge of +1?
Easy
- Aproton
- Bneutron
- Celectron
- Dα particle
37.The nucleus of an atom contains protons and neutrons.
Easy
True or false?
38.Which two particles have approximately the same relative mass?
Easy
- Aproton and neutron
- Bproton and electron
- Cneutron and electron
- Delectron and α particle
39.Isotopes of an element have the same number of protons but different numbers of neutrons.
Easy
True or false?
40.Arrange the following particles in order of increasing relative mass (smallest first).
Easy
- electron
- proton
- neutron
41.In Rutherford's α scattering experiment, what did the small number of α particles that bounced back indicate?
Medium
- AThe atom is mostly empty space.
- BThe nucleus is very small and dense.
- CThe nucleus is positively charged.
- DElectrons orbit the nucleus.
42.Nuclear fusion is the splitting of a large nucleus into two smaller nuclei.
Easy
True or false?
43.Match each particle to its relative charge.
Easy
- proton
- neutron
- electron
- +1
- 0
- -1
44.Select all the statements that are true about the Rutherford α scattering experiment.
Medium
- AMost α particles passed straight through the foil.
- BSome α particles were deflected by the nucleus.
- CA few α particles bounced back off the foil.
- DThe experiment confirmed the plum pudding model.
- Eα particles are positively charged.
45.Arrange the following events in the order they occur during nuclear fission of uranium-235. (1 = first, 2 = second, 3 = third, 4 = fourth)
Medium
- A neutron is absorbed by the uranium nucleus.
- The uranium nucleus splits into two smaller nuclei.
- Two or three neutrons are released.
- Energy is released.
46.Complete the sentence:
Easy
The number of protons in an atom is called the ____ number.
47.An atom of aluminium has a nucleon number of 27 and a proton number of 13. How many neutrons does it contain?
Easy
48.A nuclide equation for nuclear fission is: 92²³⁵U + 0¹n → 37⁹⁶Rb + 55¹³⁷Cs + N 0¹n. Calculate the number of neutrons, N, emitted.
Medium
49.An atom of aluminium has a nucleon number of 27 and a proton number of 13. How many neutrons does it contain?
Easy
- A15
- B14
- C13
- D16
50.A nuclide equation for nuclear fission is: 92²³⁵U + 0¹n → 37⁹⁶Rb + 55¹³⁷Cs + N 0¹n. Calculate the number of neutrons, N, emitted.
Medium
- A4
- B2
- C5
- D3

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