WJEC Chemistry for AS Level Student Book: 2nd Edition (Draft)

You should be able to demonstrate and apply knowledge and understanding of the: ▪ Nature of radioactive decay and the resulting changes in atomic number and mass number (including positron emission and electron capture). ▪ Behaviour of α -, β - and γ -radiation in electric and magnetic fields and their relative penetrating power. ▪ Half-life of radioactive decay. ▪ Adverse consequences for living cells of exposure to radiation and use of radioisotopes in many contexts, including health, medicine, radio-dating, industry and analysis. ▪ Significance of standard molar ionisation energies of gaseous atoms and their variation from one element to another. ▪ Link between successive ionisation energy values and electronic structure. ▪ Shapes of s- and p-orbitals and the order of s-, p- and d-orbital occupation for elements 1–36. ▪ Origin of emission and absorption spectra in terms of electron transitions between atomic energy levels. ▪ Atomic emission spectrum of the hydrogen atom. ▪ Relationship between energy and frequency ( E = hf ) and that between frequency and wavelength ( f = c / λ ). ▪ Order of increasing energy of infrared, visible and ultraviolet light. ▪ Significance of the frequency of the convergence limit of the Lyman series and its relationship with the ionisation energy of the hydrogen atom. internal structure comprising protons, neutrons and electrons. Protons and neutrons are made from quarks, and electrons belong to the lepton particle family. This unit looks at protons, neutrons and electrons. It shows what happens when an unstable atom splits to form smaller particles and how ionisation energies and emission spectra provide evidence for electronic configuration. Chemistry is the study of how matter behaves. We know that all matter is made up of very small particles called atoms. The idea of atoms was put forward by the Greeks in the fifth century BCE but it was not until the nineteenth and early twentieth century that scientists showed that matter is made up of atoms and atoms have an 1.2 Basic ideas about atoms

1.2

Topic contents 17 Atomic structure 18 Radioactivity

22 Electronic structure 24 Ionisation energies 27 Emission and absorption spectra 30 Test yourself

Maths skills • Use fractions and percentages in calculations. • Make use of appropriate units in calculations. • Use an appropriate number of significant figures. • Substitute numerical values into algebraic equations. • Change the subject of an equation. 16 DRAFT