1. 5.1.1.3 The development of the model of the atom (common content with physics)
1.1. Models of the atom
1.1.1. SPHERE MODEL Before the discovery of the electron, atoms were thought to be tiny spheres that could not be divided.
1.1.2. PLUM PUDDING MODEL The discovery of the electron led to the plum pudding model of the atom. The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it.
1.1.2.1. the difference between the plum pudding model of the atom and the nuclear model of the atom.
1.1.3. NUCLEAR MODEL The results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was charged. This nuclear model replaced the plum pudding model.
1.1.3.1. The experimental work of James Chadwick provided the evidence to show the existence of neutrons within the nucleus. This was about 20 years after the nucleus became an accepted scientific idea.
1.1.3.2. why the new evidence from the scattering experiment led to a change in the atomic model
1.1.3.3. 5.1.1.4 Relative electrical charges of subatomic particles The relative electrical charges of the particles in atoms are: PROTON +1; nEUTRON 0, ELECTRON -1 In an atom, the number of electrons is equal to the number of protons in the nucleus. Atoms have no overall electrical charge. The number of protons in an atom of an element is its atomic number. All atoms of a particular element have the same number of protons. Atoms of different elements have different numbers of protons.
1.1.3.3.1. Students should be able to use the nuclear model to describe atoms.
1.1.3.3.2. ISOTOPES Atoms of the same element can have different numbers of neutrons; these atoms are called isotopes of that element.
1.1.3.3.3. ATOMIC NUMBER The number of protons
1.1.3.4. 5.1.1.5 Size and mass of atoms Atoms are very small, having a radius of about 0.1 nm (1 x 10-10 m). The radius of a nucleus is less than 1/10 000 of that of the atom(about 1 x 10-14 m). Almost all of the mass of an atom is in the nucleus. The relative masses of protons IS 1, neutrons IS 1 and electrons VERY SMALL.
1.1.3.4.1. MASS NUMBER The sum of the protons and neutrons in an atom is its mass number.
1.1.3.4.2. Use SI units and the prefix nano.
1.1.3.4.3. Recognise expressions in standard form.
1.1.4. BOHR MODEL Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations. Later experiments led to the idea that the positive charge of any nucleus could be subdivided into a whole number of smaller particles,each particle having the same amount of positive charge. The name proton was given to these particles.
1.1.4.1. 5.1.1.7 Electronic structure 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 showing two electrons in the lowest energy level, eight in the second energy level and one in the third energy level.
1.1.4.1.1. Students should be able to represent the electronic structures of the first twenty elements of the periodic table in both forms.
1.1.4.1.2. MS 5b Visualise and represent 2D and 3D forms including twodimensional representations of 3D objects.
1.1.4.2. 4.1.1.7 Electronic structure 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
1.2. WS 1.1, 1.6 This historical context provides an opportunity for students to show an understanding of why and describe how scientific methods and theories develop over time. WS 1.2
2. 4.1.3 Properties of transition metals (chemistry only)
2.1. 4.1.3.1 Comparison with Group 1 elements The transition elements are metals with similar properties which are different from those of the elements in Group 1.
2.1.1. Students should be able to describe the difference compared with Group 1 in melting points, densities, strength, hardness and reactivity with oxygen, water and halogens. Students should be able to exemplify these general properties by reference to Cr, Mn, Fe, Co, Ni, Cu.
2.2. 4.1.3.2 Typical properties Many transition elements have ions with different charges, form colored compounds and are useful as catalysts.
2.2.1. Students should be able to exemplify these general properties by reference to compounds of Cr, Mn, Fe, Co, Ni, Cu.
3. 5.1.1.1 Atoms, elements and compounds
3.1. ATOMS All substances are made of atoms. An atom is the smallest part of an element that can exist. Atoms of each element are represented by a chemical symbol, eg O represents an atom of oxygen, Na represents an atom of sodium
3.2. ELEMENT There are about 100 different elements. Elements are shown in the periodic table.
3.2.1. use the names and symbols of the first 20 elements in the periodic table, the elements in Groups 1 and 7, and other elements in this specification
3.3. COMPOUNDS Compounds contain two or more elements chemically combined in fixed proportions and can be represented by formulae using the symbols of the atoms from which they were formed. Compounds can only be separated into elements by chemical reactions.
3.3.1. CHEMICAL REACTIONCompounds are formed from elements by chemical reactions. Chemical reactions always involve the formation of one or more new substances, and often involve a detectable energy change
3.3.1.1. WORD EQUATIONS Chemical reactions can be represented by word equations or equations using symbols and formulae.
3.3.1.1.1. write word equations for the reactions
3.3.1.2. SYMBOL EQUATIONS
3.3.1.2.1. Write formulae and balanced chemical equations for the reactions
3.3.2. name compounds of the first 20 elements from given formulae or symbol equations
3.3.3. MOLECULES
4. 5.1.1.2 Mixtures
4.1. A mixture consists of two or more elements or compounds not chemically combined together. The chemical properties of each substance in the mixture are unchanged.
4.1.1. Mixtures can be separated by physical processes that do not involve chemical reactions and no new substances are made.
4.1.1.1. filtration
4.1.1.2. crystallisation
4.1.1.3. distillation
4.1.1.3.1. fractional distillation
4.1.1.3.2. simple distillation
4.1.1.4. chromatography.
4.1.1.5. describe, explain and give examples of the specified processes of separation
4.1.1.6. suggest suitable separation and purification techniques for mixtures when given appropriate information.
4.1.2. WS 2.2, 2.3 AT 4 Safe use of a range of equipment to separate chemical mixtures.