C3aL2  The Modern Periodic Table

Key Words

Alkali Earth Metals - Elements in Group II

Alkali Metals - elements of Group I

Atomic number  - number of protons

Halogens - Group 7, consisting of fluorine, chlorine, bromine, etc.

Noble gases - Group 0 elements, unreactive gases

Proton - a positively charged particle in the nucleus

Reactivity - how reactive an element is.

Grade E

To see a modern periodic table, go to http://www.webelements.com/ .

Image from Art Branch Inc

1372 - 2384 Yonge St.
Toronto, Ontario M4P 3J4
Canada
 

Click on the link http://www.privatehand.com/flash/elements.html  to go to Tom Lehrer's Periodic table song.

Grade C

The elements of the periodic table are arranged in the order of the atomic number, the number of protons.  You can have different numbers of neutrons in the nucleus to give isotopes.  If you change the protons, you change the element.  Experiments in the early Twentieth Century enabled scientists to determine the number of protons.

The number of protons determines the number of electrons.  The electrons are involved in chemical reactions; the nucleus is never involved.

The Groups have elements that have the same number of electrons in the outer shell.  Group I elements (in yellow) have one electron in the outer shell.  As you go down the group, the outer shell electron gets less tightly held, making the reactivity of each element higher.

On the right hand side, you see the elements in white, 15 in all.  They are non metals.  The halogens, Group VII,  have 7 electrons in the outer shell.  Since the maximum that can be accommodated in the outer shell is 8, it is easier for them to gain 1 electron than to shed 7 electrons.  The reactivity of the halogens goes down as you go down the Group. 

The group number reflects the number of outer shell electrons.

If you go across the Periodic Table, you follow the Periods.  The trend across a period is for the reactivity to decrease, as the number of outer shell electrons increases.  The alkali earth metals, Group II, as less reactive than Group I metals as they have two electrons to lose, which is harder than one.  The same is true between Groups VI and VII.  The halogens are more reactive because it's easier to gain one electron than two

Grade A

The Group 0 (or Group VIII) have a full outer electron shell, so they are very unreactive.  They are often called the Noble gases or the inert gases.

Some elements, such as the those in Lanthanides and Actinides, are made artificially by bombarding the nuclei of other elements with alpha particles.  Their names, like unniloctium (Unn), are as contrived as the elements themselves.  Most of them are very unstable, with half-lives of a fraction of a second.  They have no use whatever, other than scientific curiosities that only exist in the nuclear bear-garden of a reactor.