Elements p. 33

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 Chemical symbol Element Name Iron Atomic Mass 55.847

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.

Summary 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

Where do Elements come from? Elements are the simplest substances from which other forms of matter made. The sun is made up of mostly one element: Hydrogen. It exists at tremendously high pressures and at temperatures as hot as 15 million degrees celsius.

In conditions such as these, matter cannot exist as a solid, liquid, or gas, Instead it is plasma. Plasma—a state of matter that consists of a gas-like mixture of free electrons & nuclei of atoms that have been stripped of all electrons.

Nuclear Fusion: a process in which 2 atomic nuclei combine, forming a larger nucleus and releasing huge amounts of energy. This process combines smaller nuclei into larger nuclei, creating heavier elements. These heavier elements include carbon, nitrogen and oxygen

Summary Nuclear fusion combines smaller nuclei into larger ones. To get energy powerful enough to create these heavy elements, a Supernova occurs. These elements are blown into space. Supernovas create the heavy elements such as carbon, nitrogen, and oxygen.