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neurologyYou need to know

• The first 20 elements are hydrogen (H), helium (He), lithium (Li), beryllium (Be), boron (B), carbon (C), nitrogen (N), oxygen (O), fluorine (F), neon (Ne), sodium (Na), magnesium (Mg), aluminium (Al), silicon (Si), phosphorus (P), sulfur (S), chlorine (Cl), argon (Ar), potassium (K), and calcium (Ca).
• The Group 1 elements are hydrogen (H), lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).
• Hydrogen is in Group 1, but it is not an alkali metal; the alkali metals are lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr).
• The elements called Group 7 in the school numbering system, corresponding to modern Group 17, are fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts), and these elements are known as the halogens.
• Atoms are the smallest particles of an element that retain its properties.
• Elements are pure substances made of only one type of atom.
• Compounds are substances formed from two or more elements chemically bonded together.
• The particle model describes the arrangement and movement of particles in solids, liquids, and gases.
• Atoms, elements, and compounds have different physical and chemical properties due to their structure.
• Mixtures are combinations of two or more substances that are not chemically bonded.
• The atomic model has changed over time due to new experimental evidence.
• Thomson's plum-pudding model described atoms as spheres of positive charge with embedded electrons.
• Rutherford's nuclear model proposed a small, dense, positively charged nucleus with electrons orbiting around it.
• Bohr's model introduced energy levels (shells) for electrons.
• Chadwick discovered the neutron, leading to the modern atomic model.
• Protons are located in the nucleus, have a relative charge of +1, and a relative mass of 1.
• Neutrons are located in the nucleus, have a relative charge of 0, and a relative mass of 1.
• Electrons are located in shells around the nucleus, have a relative charge of -1, and a relative mass of approximately `\frac{1}{1836}`.
• Atomic number is the number of protons in an atom.
• Mass number is the total number of protons and neutrons in an atom.
• Atoms are neutral because they have equal numbers of protons and electrons.
• For the first 20 elements, electron structures are written using 2 in the first shell, up to 8 in the second shell, and up to 8 in the third shell before the fourth shell begins.
• Ions are atoms or molecules that have gained or lost electrons and thus have a charge.
• Isotopes are atoms of the same element with different numbers of neutrons.
• The relative atomic mass of an element is the weighted average of the masses of its isotopes.
• In a chemical reaction, atoms are rearranged to form new substances, but no atoms are created or destroyed (law of conservation of mass).
• The mass of reactants equals the mass of products in a chemical reaction.
• State symbols are (s) for solid, (l) for liquid, (g) for gas, and (aq) for aqueous solution.
• Filtration, crystallisation, distillation, fractional distillation, and paper chromatography are methods for separating mixtures.
• The choice of separation technique depends on the properties of the components in the mixture.
• Electron structure influences chemical reactivity, especially in terms of how easily atoms lose, gain, or share electrons.

• Write the names and chemical symbols for the first 20 elements, every Group 1 element, and every Group 7 element in the school numbering system (modern Group 17).
• Use particle diagrams to distinguish between atoms, elements, and compounds.
• Deduce the chemical formula of a substance from particle diagrams.
• Name compounds from given chemical symbol equations.
• Describe, using the particle model, the differences between atoms, elements, and compounds.
• Write word equations and balanced symbol equations, including state symbols, for chemical reactions.
• Balance given symbol equations.
• Write a balanced symbol equation with state symbols from a given word equation.
• Describe what happens to atoms during a chemical reaction, including conservation of mass.
• Compare the size and scale of atoms to objects in the physical world, using standard form where appropriate.
• Represent the electronic structures of the first 20 elements using diagrams and numbers.
• Explain how electron structure affects chemical reactivity.
• Calculate the number of protons, neutrons, and electrons in atoms, ions, and isotopes given atomic and mass numbers.
• Explain why atoms are neutral and how ions are formed by gaining or losing electrons.
• Calculate the number of electrons gained or lost from the overall charge of an ion.
• Define and give examples of ions and isotopes.
• Calculate the relative atomic mass of an element given the percentage abundance of its isotopes.
• Describe and explain how to separate mixtures using filtration, crystallisation, distillation, fractional distillation, and paper chromatography.
• Suggest and justify suitable separation and purification techniques for mixtures based on their properties.
• Compare and contrast the atomic models of Thomson, Rutherford, Bohr, and Chadwick, explaining why each model was revised.