2024 AQA GCSE Chemistry - Paper 1. Exam Questions with Complete Solutions Merged (Verified)

Atom definition The smallest component of an element Compound Two or more elements, chemically joined in fixed proportions. They can only be separated by chemical means. Mixture Two or more elements/compounds which are not chemically combined. Ways to separate mixtures - Filtration - Evaporation - Crystallisation - Simple distillation - Fractional distillation - Paper chromatography The plum and pudding model Before electrons were discovered, people thought that atoms were indivisible spheres. The plum and pudding model was the response to this; considered a sphere of positive charge with negatively charged areas spread throughout The alpha scattering experiment This was carried out by Ernest Rutherford. He fired positively charged alpha particles at a thin sheet of gold foil. The particles should have either gone straight through, or slightly deflected. However, some particles experienced significant deflections. This lead to the conclusion that the centre of the atom was positively charged, and causing the deflections. Niels Bohr He adapted the nuclear model by suggesting the electrons orbit the nucleus at specific distances, backed up with experiments. James Chadwick He proved evidence for the neutron within the nucleus around 20 years after the nucleus was an accepted idea. Proton relative mass and charge Relative mass: 1 Charge: +1 Neutron relative mass and charge Relative mass: 1 Charge: 0 Electron relative mass and charge Relative mass: very small (around 0.0005 or 1/2000) Charge: -1 Atomic number The number of protons within an atom. This defines an element, so different atomic numbers mean different elements. Mass number The sum of protons and neutrons within an atom. Atom average radius 0.1 nm (1 × 10⁻¹⁰ m) Nucleus average radius 0.00001 nm (1 × 10⁻¹⁴ m) Isotope An atom of the same element with a different number of neutrons (a different mass number but the same atomic number) Relative atomic mass when working out in terms of isotopes Relative atomic mass = Sum of (isotope abundance × isotope mass number) -------------------------------------------------- Sum of abundances of all the isotopes Highest electronic structure 2, 8, 8, 2 How the periodic table is arranged - In terms of atomic number. - Elements with the same number of electrons in the outer shell (excluding group 0) are arranged in groups (vertical columns). - Elements with the same number of shells are arranged in periods (horizontal rows). - Elements in the same groups have similar properties. How the periodic table was arranged before Mendeleev In terms of atomic weight. This didn't work, as not all elements had been discovered and isotopes were ruining the periodic table (although these had not been discovered yet). Dmitri Mendeleev He ordered the periodic table in t