Guided Tour of the Periodic Table

Properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number, or number of protons in their atoms.

How does this pattern appear when put into a table?

Groups

Peri

ods

Groups (also called families) are the vertical columns of elements in the periodic tablePeriods are the horizontal rows of elements in the periodic table

Periodic Table Applet

Remember: The valence electrons are the ones at the outermost energy level of an atom

Remember: There are usually the same number of protons as electrons in an atom and no overall charge

An ion is an atom that has gained or lost electrons from its valence shell and therefore has a positive or negative charge

Most atoms LOVE to have a full valence shell

Lithium atom0 charge

Lithium ion+1 charge

Ions that have a positive charge are called “cations”

Fluorine atom0 charge

Fluorine ion-1 charge

Ions that have a negative charge are called “anions”

Atomic number (Z): # of protons in an atom

Atomic mass: # of protons and neutrons in an atom (why isn’t it a whole number?)

An isotope is any atom having the same number of protons, but having different numbers of neutrons within its nucleus

Atomic mass (amu)

Atomic number

Subtract the (rounded) atomic number from the atomic mass of the atom:

# neutrons = atomic mass – Z Example: Calculate the number of neutrons

contained in a Sodium atom (Z = 11) and mass = 22.989 amu

Round 22.989 amu to 23 amu 23 amu – 11 = 12 neutrons Sodium contains 12 neutrons.

Atomic number: 11 Name: Sodium Symbol: Na Family: Alkali Metals

Seldom found as a pure element in nature. A soft metal that can be cut with a butter knife, it reacts violently with chlorine to produce table salt. Explodes in water, producing hydrogen gas and sodium hydroxide (drano)

Atomic number: 12 Name: Magnesium Symbol: Mg Family: Alkaline Earth Metals

A common ingredient found in fireworks and in metal alloys

Atomic number: 13 Name: Aluminum Symbol: Al Family: Other metals

Mined from earth in the mineral bauxite. Light, recyclable, but not very strong. The oxidized form of the element is the basis of rubies and sapphires

Atomic number: 14 Name: Silicon Symbol: Si Family: Semiconductors

The third most abundant element in the earth. The oxidized form of this element is the basis for glass. Used widely in the electronics industry for its use in integrated circuits

Atomic number: 15 Name: Phosphorus Symbol: P Family: Nonmetals

An essential component in living systems. Originally extracted from urine, but is obtained through phosphate minerals nowadays. The white variety catches fire spontaneously in air and water won’t wash the burning material from the skin. For this reason, it was first used as a weapon during World War I and continues to be used in warfare today.