Monday, October 5th, 2009

Today we saw a new theme: the periodic table.

First the teacher shows us a little bit of the past:

· 1860, only 60 elements were known.

· They knew only the basic stuff.

· Jöns Jakob Berzelius- made the 2 letter system for elements.

· Johann Döbereiner- was the 1^st to “organize” the periodic table by the Law of Triads (groups of 3 elements because of their property.)

· John Newlands- use the Law of Octaves (groups of 8 elements), and he relate it with music scales.

· Mendeleev- He was the real 1^st one who made a periodic table with 12 columns and 8 rows, also we left blank spaces – he predicts the properties of the missing elements. He was considered “Chemist of predictions.”

· Henry Moseley- he organized it by atomic numbers.

As well, teacher Ariel explained us the 2 letter system for elements, that is to use the first letter of the name in English; but also why some elements are not in that system, and that’s because some elements were first written in Latin and they kept that name like gold (Au) means Aurum in Latin, and after that, he gave us a list of the 5 elements in Latin:

*Aurum (Au) = Gold

*Kabium (K) = Potassium

*Natium (Na) = Sodium

*Ferrum (Fe) = Iron

*Argentums (Ag) = Silver

· Of all the elements, 83 elements are stable in nature, while 24 are not from earth.

Now, the periodical table is conformed of rows (horizontal) and columns (Vertical):

The horizontal are the Periods-the mass and size are similar in each period.

The vertical are the Groups, and in these one are different classification:

1) Alkali Metal

2) Alkali earth metal

11) Coinage Metal- soft metals (gold, silver and copper)

17) Halogens- they separate vey easy.

18) Zero, Noble gases, Inert gases- the ones that are stable.

· Periodical table also use the electronic configuration helping you find a element more quick; the periods will be used as the biggest number of the list, example: if you got as the biggest one 3p⁴, then the period will be #3; and the groups are represented in these way:

Andrea Favela