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Fundamental concepts of chemistry
chemical formula, chemical equation, proton, neutron, element, electron, atomic nucleus, molecule, cation, anion, chemical compound, chemical reaction, chemical bonds, ion, molecule, atomic number An atom is a collection of matter consisting of a positively charged core (the ________________) which contains ____________ and ____________ and which maintains a number of electrons to balance the positive charge in the nucleus. The atom is also the smallest portion into which an ____________ can be divided and still retain its properties, made up of a dense, positively charged nucleus surrounded by a system of ____________.
An ____________ is an atom or a molecule that has lost or gained one or more electrons. Positively charged ____________ (e.g. sodium cation Na+) and negatively charged ___________ (e.g. chloride Cl−) can form neutral salts (e.g. sodium chloride NaCl). Electrical forces at the atomic level create _____________ __________ that join two or more atoms together, forming ____________. Some molecules consist of atoms of a single element.
When atoms of two or more different elements bond together, they form a ____________________. Water is a compound made up of two hydrogen atoms and one oxygen atom. The __________ _________ for a water molecule is H2O. Compounds are formed or broken down by means of ____________ __________. All chemical reactions involve the formation or destruction of chemical bonds. Chemists use ___________ ___________ to express what occurs in chemical reactions. Chemical equations consist of chemical formulas and symbols that show the substances involved in chemical change. For example, the equation C + O2 = CO2 expresses the chemical change that occurs when one carbon atom reacts, or bonds, with an oxygen molecule. The reaction produces one molecule of carbon dioxide, which has the formula CO2. Tasks
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