2. elements A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. The term is also used to refer to a pure chemical substance composed of atoms with the same number of protons.[1
3. atoms The atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons (except in the case of hydrogen1 which is the only stable nuclide with no neutron).
4. Metals and Non-metals. Non-metal, or non-metal, is a term used in chemistry when classifying the chemical elements. On the basis of their general physical and chemical properties, every element in the periodic table can be termed either a metal or a non-metal. (A few elements with intermediate properties are referred to as metalloids.)
5. Compounds A chemical compound is a pure chemical substance consisting of two or more different chemical elementsthat can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms[3] that are held together in a defined spatial arrangement by chemical bonds. Chemical compounds can be compound molecules held together by covalent bonds, salts held together by ionic bonds, metallic compounds held together by metallic bonds, or complexes held together by coordinate covalent bonds. Substances such as pure chemical elements and elemental molecules consisting of multiple atoms of a single element (such as H2, S8, etc.) are not considered chemical compounds.[5]
6. Chemical reactions A chemicalreaction is a process that leads to the transformation of one set of chemical substances to another.[1]. They are studied by chemists under a field of science called chemistry. It can be either spontaneous that is requiring no input of energy or non-spontaneous, that often comes about only after input of some form of energy, viz. heat, light or electricity.
7. Reaction rate The reactionrate or rate of reaction for a reactant or product in a particular reaction is intuitively defined as how fast a reaction takes place. For example, the oxidation of iron under the atmosphere is a slow reaction which can take many years, but the combustion of butane in a fire is a reaction that takes place in fractions of a second. Chemical kinetics is the part of physical chemistry that studies reaction rates. The concepts of chemical kinetics are applied in many disciplines, such as chemical engineering, enzymologist and environmental engineering.
8. Chemical reactions A chemicalreaction is a process that leads to the transformation of one set of chemical substances to another.[1]. They are studied by chemists under a field of science called chemistry. It can be either spontaneous that is requiring no input of energy or non-spontaneous, that often comes about only after input of some form of energy. A chemical reactions
9. Chemical changes ChemicalChanges Chemical changes take place on the molecular level. A chemical change produces a new substance. Examples of chemical changes include combustion (burning), cooking an egg, rusting of an iron pan, and mixing hydrochloric acid and sodium hydroxide to make salt and water. Physical changes Physical changes are concerned with energy and states of matter. A physical change does not produce a new substance. Changes in state or phase (melting, freezing, vaporization, condensation, sublimation) are physical changes. Examples of physical changes include crushing a can, melting an ice cube, and breaking a bottle.
