Elements, Atoms, <br />Compounds and Molecules<br />By An He<br />
Elements<br />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.<br />
Atom<br />The Atom is a basic unit of matter consisting of a dense, central nucleus surrounded by a cloud of negatively charged electrons.<br />Mass range: 1.67 × 10−27 to 4.52 × 10−25 kg.<br />Electric charge: zero (neutral), or ion charge.<br />Diameter range: 62 pm (He) to 520 pm (Cs) (data page)<br />Components Electrons and a compact nucleus of protons and neutrons<br />
Metals<br />Chemical Properties<br /><ul><li>Usually have 1-3 electrons in their outer shell.
Solid at room temperature (except Hg). </li></li></ul><li>non-metals<br />Chemical Properties<br />Usually have 4-8 electrons in their outer shell. <br />Gain or share valence electrons easily. <br />Form oxides that are acidic. <br />Are good oxidizing agents. <br />Have higher electro negativities.<br />Physical Properties<br />Poor conductors of heat and electricity. <br />Brittle - if a solid. <br />No ductile. <br />Do not possess metallic luster. <br />Transparent as a thin sheet. <br />Solids, liquids or gases at room temperature.<br />
The Periodic Table<br />The periodic table of the chemical elements (also, Mendeleev's table, periodic table of the elements or just periodic table) is a tabular display of the chemical elements. Although precursors to this table exist, its invention is generally credited to Russian chemist Dmitri Mendeleev in 1869, who intended the table to illustrate recurring ("periodic") trends in the properties of the elements. The layout of the table has been refined and extended over time, as new elements have been discovered, and new theoretical models have been developed to explain chemical behavior.<br />