IB Chemistry - Atomic Theory

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Syllabus ref: 2.2 Syllabus ref: 12.1

When Isaac Newton first employed a glass prism to break sunlight into its constituent colours, little did he know that he was experimenting with the very tool that subsequent scientists were to use to explore the inner secrets of the smallest fundamental particles of nature, the atoms.

Nature of science:

Developments in scientific research follow improvements in apparatus-the use of electricity and magnetism in Thomson's cathode rays.

Theories being superseded-quantum mechanics is among the most current models of the atom.

Use theories to explain natural phenomena-line spectra explained by the Bohr model of the atom

Understandings - SL

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

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.

Sub-levels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron.

Each orbital has a defined energy state for a given electronic configuration and chemical environment and can hold two electrons of opposite spin.

Understandings - HL

Essential idea: The quantized nature of energy transitions is related to the energy states of electrons in atoms and molecules.

In an emission spectrum, the limit of convergence at higher frequency corresponds to the first ionization energy.

Trends in first ionization energy across periods account for the existence of main energy levels and sub-levels in atoms.

Successive ionization energy data for an element give information that shows relations to electron configurations.

Applications and skills - SL

Description of the relationship between colour, wavelength, frequency and energy across the electromagnetic spectrum

Distinction between a continuous spectrum and a line spectrum. 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.

Recognition of the shape of an s atomic orbital and the px, py and pz atomic orbitals.

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.

Applications and skills - HL

Solving problems using E = hv.

Calculation of the value of the first ionization energy from spectral data which gives the wavelength or frequency of the convergence limit.

Deduction of the group of an element from its successive ionization energy data.

Explanation of the trends and discontinuities in first ionization energy across a period.

In Chapter 1.3