Atoms and isotopes Revision - AQA Physics 8463

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34 objective pages available

The structure of an atom11 objectives

Describe atoms as very small particles with a radius of about 1 x 10^-10 metres.
Describe the nucleus as the small central part of an atom.
State that the nucleus contains protons and neutrons.
State that nearly all the mass of an atom is concentrated in the nucleus.
Describe electrons as negatively charged particles arranged in shells or energy levels around the nucleus.
Compare the relative charges of protons, neutrons and electrons.
Compare the relative masses of protons, neutrons and electrons.
Explain why an atom has no overall electrical charge when it contains equal numbers of protons and electrons.
Explain that atoms can form ions by losing or gaining electrons.
Determine the numbers of protons, neutrons and electrons in simple atoms and ions.
Use atomic structure to explain the difference between a neutral atom and a charged ion.

Mass number, atomic number and isotopes11 objectives

Define atomic number as the number of protons in the nucleus of an atom.
Define mass number as the total number of protons and neutrons in the nucleus of an atom.
Calculate the number of neutrons using mass number minus atomic number.
Define isotopes as atoms of the same element with different numbers of neutrons.
Explain that isotopes of an element have the same number of protons.
Explain that isotopes of an element have different mass numbers because they contain different numbers of neutrons.
Explain why isotopes of the same element have the same chemical properties.
Interpret isotope notation using atomic number and mass number.
Compare the composition of two isotopes of the same element.
Describe radioactive isotopes as isotopes with unstable nuclei.
Explain that unstable nuclei may emit radiation to become more stable.

The development of the model of the atom12 objectives

Describe the early model of the atom as a tiny indivisible sphere.
Describe how the discovery of the electron led to the plum pudding model.
Describe the plum pudding model as a ball of positive charge with negative electrons embedded in it.
Describe the alpha particle scattering experiment carried out by Geiger and Marsden.
Explain why most alpha particles passing straight through gold foil suggested that atoms are mostly empty space.
Explain why some alpha particles being deflected suggested that positive charge is concentrated in a small nucleus.
Explain why a few alpha particles bouncing back suggested that most of the atom's mass is concentrated in the nucleus.
Describe how alpha scattering evidence led to the nuclear model replacing the plum pudding model.
Describe how Bohr adapted the nuclear model by suggesting that electrons orbit at specific distances or energy levels.
Describe how later evidence led to the idea that the positive charge of the nucleus can be divided into whole numbers of protons.
Describe how Chadwick's work provided evidence for the neutron.
Use evidence to compare the plum pudding model, nuclear model and modern atomic model.

atomnucleusprotonelectronneutronIonElectronneutral atomcharged ionatomic numbermass numberisotope

Understand Atomic Size: Explain connect The structure of an atom to the exact command in the question: remember that atoms are extremely small, with a radius of about 1 x 10^-10 metres. Visualize this scale to grasp their size relative to everyday objects.
Understand the Nucleus: Compare connect The structure of an atom to the exact command in the question: remember that the nucleus is the small central part of an atom, containing protons and neutrons.

Misinterpreting Atomic Size: Explain that 1 × 10⁻¹⁰ m is an average value for a typical neutral atom; actual radii differ between elements and depend on factors such as nuclear charge and electron shielding.
Nucleus Size Misconception: Emphasize that the nucleus is actually very small compared to the overall size of the atom, which is mostly empty space.

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