Chemistry Glossary

Chemistry Glossary                      electron affinity: the energy associated with the uptake of an electron by an atomin the gaseous state, thus forming a charged ion –1. quaternary C atom: a C atom bonded to 4 other C atoms. primary C atom: the C atom that is bonded to 1 other C atom. secondary C atom: a C atom bonded to 2 other C atoms. tertiary C atom: a C atom bonded to 3 other C atoms. octet rule: the tendency for other elements to achieve a noble gas configuration by forming bonds in order to match their electron configuration with that of the nearest noble gas. Oxidation number: a number indicating the ability of an atom to lose or gain electrons in the formation of a compound. octane number: a number that indicates the quality of a gasoline. Electron: The elementary particle that makes up an atom that has a negative charge. Electrons surround the atomic nucleus in atomic shells. valence electrons: electrons in the outermost shell. Valence electrons play an important role in forming bonds with other atoms and determining chemical properties atom. ionization energy: the energy required to remove an electron from a neutral atom in the gaseous state. The energy required to remove the second electron is called the second ionization energy and so on. noble gases: group VIIIA elements, a group of elements that are very stable (hard to react). groups: vertical columns in the SPU, namely groups of elements arranged based on similar properties. The group number of an element = the number of valence electrons of that element. halogens: group VIIA elements, the most reactive non-metallic group of elements. hydrate:a solid crystalline compound containing crystalline water (HO ). hydrocarbons: the simplest carbon compounds consisting of carbon atoms and hydrogen. Avogadro's hypothesis: a hypothesis which states that at the same temperature andpressure, all gases with the same volume will contain the same number of molecules as well. law of conservation of mass (Lavoisier's law): a chemical law which states that in a chemicalreaction, the mass of the substances before and after the reaction is The same. law of multiple ratios (Dalton's law): a chemical law which states that if two types of elements combine to form more than one compound and if the masses of one of the elements in the compounds are the same, while the masses of the other elements are different, then the mass ratio of the elements The rest in these compounds are simple integers. law of fixed proportions (Proust's law): a chemical law which states that the mass ratio of elementsin a compound is fixed. law of volume ratio (Gay Lussac's law): a chemical law which states that at the same temperature and pressure, the volumes of the reacting gases and the volumes of the reacting gases are proportional as simple whole numbers. law of octaves: the periodic system of elements based on increasing relative atomic masses, in which the first and eighth order elements (one octave apart) show similar properties.                      ionic bond: bond formed by the transfer of electrons from one atom to another. Ionic bonds are formed between atoms that give up electrons (metals) and atoms that gain electrons (nonmetals). chemical bond: the force that binds the atoms in a molecule or ionic combination in any compound. covalent bond: a bond formed by the sharing of a pair of electrons shared by two atoms. coordinate covalent bond: a covalent bond in which a shared pair of electrons is contributed by only one atom, while the other atom does not donate electrons. nonpolar covalent bonds: bonds between atoms with the same electronegativity. polar covalent bond: bond between two atoms with different electronegativities. atomic nucleus: the solid part of the atom, located at the center of the atom. The atomic nucleus is charged positive. isobars: atoms of different elements, but have the same mass number. isotones: atoms of different elements, but have the same number of neutrons. isotopes: atoms of the same element, but different masses. The difference in mass is due to the difference in the number of neutrons. Atoms of the same element can have different numbers of neutrons. atomic radius: the distance from the nucleus to the outer shell. electronegativity: a number that expresses the tendency of an element to attract electrons to its side in a bond. organic chemistry: a branch of chemistry that studies organic carbon compounds. Organic chemistry is also known as carbon chemistry. electron configuration: the arrangement of electrons in each shell. coefficient reaction: a number that expresses the stoichiometric mole ratio of the reactants and the products of the reaction. Lewis symbol: symbol for an atom with its valence electrons. Electrons in the Lewis symbol can be represented by dots or small crosses. electrolyte solution: a solution that can conduct electricity. alkali metals: metal elements of group IA, the most active metal group. alkaline earth metals: group IIA elements, also classified as active metals but less active than the alkali metals of the same period. molar mass (mm): the mass possessed by one mole of a substance and has units of grams mole. atomic model: a model (fiction) put forward by experts to replace the real atom that cannot be observed. moles of substance (n): the amount of substance that contains the same number of particles as the number of particles in 12 grams of C–12. Neutron: The basic particle that makes up an atom that is neutral. Neutrons are in atomic nucleus. atomic number (Z): the number of protons in the nucleus. The atomic number is unique for each element.                           mass number (A): the number of protons + neutrons. The mass of the electron is very small, it can be neglected. nucleon: the particle that makes up the nucleus of an atom. Nucleons consist of protons and neutrons. oxidation: binding of oxygen, loss of electrons, increase in oxidation number. limiting reagent: the reactant that gets used up first in a chemical reaction. period: horizontal stripes in SPU. In modern SPU, the periods are arranged in order of increasing atomic number. The period number of an element = the number of valence electrons of that element. reaction equation: an equation that describes the chemical substances involved before and after a chemical reaction, both qualitatively and quantitatively. petrochemicals: oil and gas-based industrial products. Examples of petrochemicals are plastics, detergents, and artificial rubber. proton: the elementary particle that makes up an atom with a positive charge. Protons are located in atomic nucleus. electromagnetic radiation: electromagnetic waves, massless radiation and unloaded. particle radiation: radiation that is the scattering of particles, such as electrons and proton. reduction: loss of oxygen, gain of electrons, and decrease in oxidation number. empirical formula: a chemical formula that expresses the simplest ratio of the elemental atoms in a compound. chemical formula: a formula that contains information about the type of element and the ratio of the atoms of the elements that make up the substance. molecular formula: a chemical formula that states the types and ratios of atoms in a molecule. binary compound: a chemical compound composed of only two elements. alpha rays: radioactive rays that have a positive charge. Alpha rays are helium nuclei. beta rays: radioactive rays that are negatively charged. Beta rays are electron beams. gamma rays: radioactive rays which are electromagnetic waves. cathode rays: radiationof particles originating from the anode surface towards the cathode. The cathode ray particles are electrons. canal beam: particle radiation originating from the surface of the anode towards the cathode. The channel beam particles depend on the gas in the tube. Hydrogen gas produces protons. periodic system of elements: a list of elements arranged according to certain rules. TEL: an additive added to gasoline to increase the octane number gas. triad: a periodic system of elements consisting of three elements that are similar in properties. If three elements with similar properties are arranged in order of increasing atomic mass, then the atomic mass of the element in the middle is the average of the atomic masses of the first and third elements. Triad discovered by Dobereiner. main group elements: elements that occupy group A. transition elements: elements that occupy group B. molar volume of gas (Vm): volume occupied by 1 mole of gas at a certain temperature (T) and pressure (P) .  radioactive substance: a substance that spontaneously emits radiation.