Elements and the Periodic Table

• A classification scheme for matter.

• Names of Elements– The first 103 elements have internationally accepted

names, which are derived from:• The compound or substance in which the element was

discovered

• An unusual or identifying property of the element

• Places, cities, and countries

• Famous scientists

• Greek mythology

• Astronomical objects.

• The elements of aluminum, Iron, Oxygen, and Silicon make up about 88 percent of the earth's solid surface. Water on the surface and in the air as clouds and fog is made up of hydrogen and oxygen. The air is 99 percent nitrogen and oxygen. Hydrogen, oxygen, and carbon make up 97 percent of a person. Thus almost everything you see in this picture us made up of just six elements.

– Chemical Symbols• There are about a dozen common elements that have a

single capitalized letter for their symbol• The rest, that have permanent names have two letters.

– the first is capitalized and the second is lower case.• Some elements have symbols from their Latin names.•

SymbolAtomic Mass

Atomic Number

Charge (if ion)

HHydrogenHydrogen

1

1

Protons: 1Neutrons: 0Electrons: 1

NaSodiumSodium

23

11

Protons: 11Neutrons: 12Electrons: 11

• The Modern Periodic Table

• Introduction– The periodic table is made up of r 7 rows of elements and

18 columns.– An element is identified by its chemical symbol.– The number above the symbol is the atomic number– The number below the symbol is the rounded atomic

weight of the element.– A row is called a period– A column is called a group

• (A) Periods of the periodic table, and (B) groups of the periodic table.

– Group A elements are called representative elements– Group B elements are called transition elements.

• Chemical “Families”– IA are called alkali metals because the react with water

to from an alkaline solution– Group IIA are called the alkali earth metals because

they are reactive, but not as reactive as Group IA.– Group VIIA are the halogens

• These need only one electron to fill their outer shell

• They are very reactive.

– Group VIIIA are the noble gases as they have completely filled outer shells

• They are almost non reactive.

• Four chemical families of the periodic table: the alkali metals (IA), the alkaline earth metals (IIA), halogens (VII), and the noble gases (VIIIA).

Metal: Elements that are usually solids at room temperature. Most elements are metals.Non-Metal: Elements in the upper right corner of the periodic Table. Their chemical and physical properties are differentfrom metals.

Metalloid: Elements that lie on a diagonal line between the Metals and non-metals. Their chemical and physical properties are intermediate between the two.

– When an atom or molecule gain or loses an electron it becomes an ion.• A cation has lost an electron and therefore has a

positive charge• An anion has gained an electron and therefore has a

negative charge.

What would the charge be on a sodium ion?

EXAMPLE

Since sodium in in Group IA it is a metal and so wouldLOSE an electron

You can tell how many would be lost by the group numberGroup 1A elements lose 1 electron

So the charge would be +1Remember an electron is negatively charged. When you lose them atom becomes positively charged…

when you gain them it becomes negatively charged

How would you right the symbol for the sodium CATION?

EXAMPLE

Na+1

How many outer electrons does sodium have before it loses one?

It has 1…remember the group number!