Periodic Table Vocabulary Periodic Table – a chart that organizes information about all of the known elements according to their properties. Matter – anything that has mass and volume. Element – a substance that cannot be broken down into a simpler substance by ordinary chemical means. Synthetic Element – elements that are made by scientists in a laboratory and do not exist in nature. Synthetic elements are typically identified as any element with the atomic number of 93 and up. Atom – the smallest unit of an element that has all of the properties of the element; basic building block of matter. Molecule – the smallest unit of a compound that has all of the properties of the compound. Elemental Symbol – the single capital letter or capital letter followed by a lower case letter or letters that represents the name of the element. Atomic Mass – the number of protons and neutrons in the nucleus of one atom of the element. Located under the elemental symbol (at the bottom of the element box on the periodic table). Atomic Number – the number of protons contained in each nucleus of its atoms of the element. Located over the elemental symbol (at the top of the element box on the periodic table). Period – a horizontal row (left to right) in the periodic table. Group – a vertical column (up and down) on the periodic table. Reactivity – describes how likely an element is to form bonds with other elements. Valence Electrons – electrons that are located in the outermost energy level of an atom. Electron Cloud – the region surrounding the nucleus of an atom where the electrons are located. Ion – an atom that has gained or lost one or more electrons. Ionic Bond – a bond formed by the transfer of electrons (when valence electrons of one atom are transferred to the outer energy level of another atom). Covalent Bond – a bond formed when two atoms share valence electrons. Please copy the “Atomic Theory” below. The Atomic Theory States: (1) All matter is composed of atoms (2) Atoms of a given element are identical (3) Atoms of different elements combine in simple whole-number ratios to form chemical compounds. Metal – an element or substance that conducts heat and electricity. Nonmetal – an element that does not conduct electricity or heat and is usually a gas at room temperature. Metalloid – an element that has some properties of a metal and some properties of a nonmetal. Inert – elements and/or compounds that when put together are unable to react chemically. The Law of Conservation of Matter – a scientific law that states that during a chemical reaction, matter cannot be created or destroyed but can be changed into a different form.