英文化学元素周期表新.docVIP

The Periodic Table of Elements by Anthony Carpi, Ph.D. In 1869, the Russian chemist  HYPERLINK /library/pop_glossary_term.php?oid=4522l= Dmitri Mendeleev first proposed that the chemical  HYPERLINK /library/pop_glossary_term.php?oid=1510l= elements exhibited a periodicity of properties.? Mendeleev had tried to organize the chemical elements according to their atomic  HYPERLINK /library/pop_glossary_term.php?oid=3418l= weights, assuming that the properties of the elements would gradually change as  HYPERLINK /library/pop_glossary_term.php?oid=849l= atomic weight increased.? What he found, however, was that the chemical and physical properties of the elements increased gradually and then suddenly changed at distinct steps, or periods.? To account for these repeating trends, Mendeleev grouped the elements in a table that had both rows and columns.? The modern periodic table of  HYPERLINK /library/pop_glossary_term.php?oid=1510l= elements is based on Mendeleevs observations; however, instead of being organized by atomic  HYPERLINK /library/pop_glossary_term.php?oid=3418l= weight, the modern table is arranged by  HYPERLINK /library/pop_glossary_term.php?oid=1512l= atomic number (z).? As one moves from left to right in a row of the periodic table, the properties of the elements gradually change.? At the end of each row, a drastic shift occurs in chemical properties. The next element in order of atomic number is more similar (chemically speaking) to the first element in the row above it; thus a new row begins on the table.?? For example, oxygen (O), fluorine (F), and neon (Ne) (z = 8, 9 and 10, respectively) all are stable nonmetals that are gases at room temperature. Sodium (Na, z = 11), however, is a silver metal that is solid at room temperature, much like the  HYPERLINK /library/pop_glossary_term.php?oid=1510l= element lithium (z = 3). Thus sodium begins a new row in the periodic table and is placed directly beneath lithium, highlighting their