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Essential idea: The mass of an atom is concentrated in its minute, positively charged nucleus.
2.1/2.2 Sub-atomic particles and structure of an atom
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Understandings:
Atoms contain a positively charged dense nucleus composed of protons and neutrons (nucleons). Negatively charged electrons occupy the space outside the nucleus. The main energy level or shell is given an integer number, n, and can hold a maximum number of electrons, 2n2. A more detailed model of the atom describes the division of the main energy level into s, p, d and f sub-levels of successively higher energies. |
2.1 Atomic number and mass number
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Applications and skills:
Use of the nuclear symbol notation to deduce the number of protons, neutrons and electrons in atoms and ions. |
2.1 Isotopes
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Definition and properties of isotopes
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2.1 Calculating relative atomic mass
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Understandings:
The mass spectrometer is used to determine the relative atomic mass of an element from its isotopic composition. Applications and skills: Calculations involving non-integer relative atomic masses and abundance of isotopes from given data, including mass spectra. |
2.2 Atomic orbitals
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Understandings:
Sub-levels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron. Applications and skills: Recognition of the shape of an s atomic orbital and the px, py and pz atomic orbitals. |
2.2 The Aufbau principle
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Understandings:
Each orbital has a defined energy state for a given electronic configuration and chemical environment and can hold two electrons of opposite spin. Applications and skills: Application of the Aufbau principle, Hund’s rule and the Pauli exclusion principle to write electron configurations for atoms and ions up to Z = 36. Guidance: Orbital diagrams should be used to represent the character and relative energy of orbitals. |
2.2 Electron configurations
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Applications and skills:
Application of the Aufbau principle, Hund’s rule and the Pauli exclusion principle to write electron configurations for atoms and ions up to Z = 36. Guidance: Orbital diagrams should be used to represent the character and relative energy of orbitals. The electron configurations of Cr and Cu as exceptions should be covered. |
2.2 Electromagnetic spectrum
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Applications and skills:
Description of the relationship between colour, wavelength, frequency and energy across the electromagnetic spectrum. |
2.2 Line Spectra
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Applications and skills:
Distinction between a continuous spectrum and a line spectrum. |
2.2 Hydrogen emission spectrum
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Understandings:
Emission spectra are produced when photons are emitted from atoms as excited electrons return to a lower energy level. The line emission spectrum of hydrogen provides evidence for the existence of electrons in discrete energy levels, which converge at higher energies. Applications and skills: Description of the emission spectrum of the hydrogen atom, including the relationships between the lines and energy transitions to the first, second and third energy levels. |
2.2 Exceptions to the Aufbau principle
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This video covers exceptions to the Aufbau principle (Cu and Cr) as well as writing abbreviated electron configurations.
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2.2 Orbital diagrams
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Understandings:
Each orbital has a defined energy state for a given electronic configuration and chemical environment and can hold two electrons of opposite spin. Guidance: Orbital diagrams should be used to represent the character and relative energy of orbitals. |