C1 Atomic Structure Flashcards
C1.1 atoms
All substances are made up of atoms. The periodic table lists all the chemical elements, with eight main groups each containing elements with similar properties. Elements comtain only one type of atom. Compounds contain more than one type of atom. An atom has a tiny nucleus at its centre, surrounded by electrons.
C1.2 chemical equations
No new atoms are created or destroyed in a chemical reaction: the total mass of reactants = the total mass of products. There is the same number of each type of atom on each side of a balanced symbol equation. You can include state symbols to give extra information in balanced symbol equations. These are, (l) for liquids, (g) for gases, (s) for solids, and (aq) for aqueous solutions.
C1.3 separating mixtures
A mixture is made up from two or more substances that are not chemically combined together. Mixtures can be separated by physical means, such as filtration, crystallisation, and simple distillation.
C1.4 Fractional distillation and paper chromatography
Fractional distillation is an effective way of spearating miscible liquids, using a fractioning column. The separation is possible because of the different boiling points of the liquids in the mixture. Paper chromatography separates mixtures of substances dissolved in a solvent as they move up a piece of chromatography paper. The different substances are separated because of their different solubilities in the solvent used
C1.5 History of the atom
The ideas about atoms have changed over time. New evidence has been gathered from the experiments of scientists who have used their observations and calculations. Key ideas were proposed successively by Dalton, Thomas, Rutherford, and Bohr, before arriving at the current model of the atom.
C1.6 Structure of the atom
Atoms are made of protons, neutrons, and electrons. Protons have a relative charge of +1 and electrons have a relative charge of -1. Neutrons have no electric charge. They are neutral. The relative masses of a proton and neutron are both 1. Stoms contain an equal number of protons and electrons, so carry no overall charge. Atomic number = number of protons = number of electrons. Mass number = number of protons and neutrons. Atoms of the same element have the same number of protons and electrons in their atoms.
C1.7 Ions, atoms, and isotopes
Atoms that gain electrons form negative ions. If atoms lose electrons they form positive ions. Isotopes are atoms of the same element with different numbers of neutrons. They have identical chemical properties, but their physical properties, such as density, can differ
C1.8 Electronic structures
The electrons in an atom are arranged in energy levels or shells. The lowest energy level (1st shell) can hold up to 2 electrons and the next energy level (2nd shell) can hold up to 8 electrons. The 4th shell starts to fill after 8 electrons occupy the 3rd shell. The number of electrons in the outermost shell of an element’s atoms determine the way in which that element react.
