Elements p.

The first periodic table was published in 1869 by Mendeleev. The periodic table is arranged by atomic number today and no longer by atomic mass. The properties of an element can be predicted from its location in the periodic table.

Each square contains the element’s atomic #, chemical symbol, name, and atomic mass. Fe 26 Iron Atomic # Chemical symbol Element Name Atomic Mass

Periodic Table—is a chemist’s calendar Atomic Mass—the average mass of all the isotopes of an element There is a pattern of properties when the elements are arranged in order of increasing atomic mass.

Atomic # increases from left to right. Periods—horizontal rows that the table is organized into: each period contains a series of different elements. Groups—(also known as families) 18 vertical columns—elements in the same group/family have similar properties.

Elements on the left side of the periodic table are the most reactive. Elements on the right side of the periodic table are the least reactive. 4 Sentence Summary and 4 Study Questions

Summary Starter The Periodic Table of elements organizes the elements like a calendar according to their masses and other properties.

Calculating number of neutrons Atomic # = # of protons Atomic # also = # of electrons H atomic # 1 has ___ protons and ___ electrons # of neutrons = atomic mass - atomic number H atomic mass ___ - ___ = ___ neutrons