distillation and chromatography. physical processes do not involve chemical reactions and no new substances are made. to suggest suitable separation and purification techniques for them. Students can investigate how to purify dirty salty water and acquire pure salt and pure water. WS 2.2, 2.3, 4.1 5.1.1.3 New experimental evidence may lead to a scientific model being changed or replaced. Before the discovery of the electron atoms were thought to be tiny spheres that could not be divided. The discovery of the electron led to the plum-pudding model of the atom. The model suggested that the atom was a ball of positive charge with negative electrons embedded in it. The results from the alpha particle scattering experiment led to the plum-pudding model being replaced by the nuclear model. Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations Describe how and why the atomic model has changed over time. Describe the difference between the plum-pudding of the atom and the nuclear model of the atom. Describe why the new evidence from the scattering experiment led to a change in the atomic model. 1 Students can make a timeline of the scientific developments leading to the current model of the atom. Links to Physics Unit 6.7. Describe the evidence from the scattering experiment and why it led to a change in the atomic model. Compare the plum pudding model of the atom and the nuclear model of the atom. Demonstrate the difference between the plum pudding and the atomic model using a hula hoop with negative electrons hanging in it and a quadrat with gold protons stuck on the corners of the grid (see Physics Unit 6.7 Atoms and isotopes) WS 1.1, 1.2
Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element. Atoms can be represented as shown in this example: students to come up with their own improved models. WS 4.3, 4.4 Ma 1b 5.1.1.6 The relative atomic mass of an element is an average value that takes account of the abundance of the isotopes of the element. Be able to calculate the relative atomic mass of an element given the percentage abundance of its isotopes. 0.5 YouTube: 5.1.1.7 The electrons in an atom occupy the lowest available energy levels (innermost available shells). The electronic structure of an atom can be represented by numbers or by a diagram. For example, the electronic structure of sodium is 2,8,1 or Be able to represent the electronic structures of the first twenty elements of the periodic table in both forms. Students may answer questions in terms of either energy levels or shells. 0.5 Relate the numbers of electrons to the numbers of protons. Draw the electronic structure of sodium. Draw out the electronic structure of the atoms used in the previous lesson. Write out the numerical electronic structure below the shell diagram of each. Make models of the electronic structure of various elements. Suspend from string and hang from ceiling in order of numbers of electrons and electron shells. WS 1.2 Ma 5b YouTube: YouTube:
energy level, except for helium, which has only two electrons. The boiling points of the noble gases increase with increasing relative atomic mass (going down the group). 5.1.2.5 The elements in Group 1 of the periodic table are known as the alkali metals and have characteristic properties because of the single electron in their outer shell.: In Group 1, the reactivity of the elements increases going down the group. Describe the reactions of the first three alkali metals with oxygen, chlorine and water. Explain how properties of the elements in Group 1 depend on the outer shell of electrons of the atoms. Predict properties from trends down the group. 1 Define the Group 1 metals. Describe the properties and describe how the reactivity changes as you move down the group. Draw the electronic shells of the Group 1 metals and link to the reactivity. Describe how properties of the elements in Group 1 depend on the outer shell of electrons of the atoms. Predict the properties of caesium and rubidium based on their electronic structure. Demonstrate the reactivity of the Group 1 metal in water. Demonstrate that alkali metals form alkaline solutions in water using UI. Students can investigate the colours of compounds of alkali metals using flame tests. Video clip: YouTube: YouTube: 5.1.2.6 The elements in Group 7 of the periodic table are known as the halogens and have similar reactions because they all have seven electrons in their outer shell. The halogens are non-metals and Describe the nature of the compounds formed when chlorine, bromine and iodine react with metals and non-metals. 1 Define the elements of Group 7. Describe the properties of the elements in Group 7 including the electron shell configuration. Demonstrate the relative reactivities of the halogens by reacting potassium halogens solution (eg iodide) with bromine or chlorine. Video clip: YouTube: