Remember your last visit of a book store to purchase a book. You asked for a book and shopkeeper gave you within a minute. The shop was full of different books. Then how come he brought a desired book this much quickly. In book stores all books are arranged into various categories and sub-categories. They are arranged on shelves accordingly. Therefore you can easily check the location of the books. Has there been something like a bookstore in chemistry? Have you known that there are total 114 elements discovered till today.
You have learnt about atom, molecule ad compound. Terms like atomic number are mass number play an important role for collecting information about the elements. There should be some way to arrange these elements. So when you want to know about any element, you can collect all information by seeing that arrangement. Now we have a long form of the periodic table which is a tabular arrangement of element on the basis of atomic number.
Now we know about long form of the periodic table of elements but long back there was no information about all elements. Alexandre Beguyer de Chancourtois was first recognized periodicity in the physical properties of the elements in 1862. Later William Odling intrigued by atomic weights and the periodicity of the elements. Let's discuss one of the parts of the long form of the periodic table that is known as main group elements.
|Factor by Grouping|
S - block elements consists of 1 and 2 group of the periodic table. They are metals, except for Hydrogen, the first member of the group. Hydrogen is a gas and has just one electron in it. It usually forms a covalent bond, unlike other metals in the s- block.
The first group elements, from Lithium(Li), Sodium(Na), Potassium(K), Rubidium(Rb), cesium(Cs) and Francium(Fr) are all soft metals. They are called as alkali metals since they form strongly alkaline oxides and hydroxides. Francium is a radioactive element.
Alkali metals or the first A group have just one electron in their valence shell. (ns1). They are highly malleable and ductile. They are bright and give distinctive luster, when freshly cut. They are electropositive in nature and have very less first ionization constant. They produce coloration during the flame test.Lithium - Crimson red
Alkaline earth metals are Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium(Sr), Barium (Ba) and Radium(Ra). The oxides of the three metals, Ca, Sr and Ba were known much earlier than the metals themselves and were called alkaline earths, since they were alkaline in character and occurred in nature as earths- Lime(CaO), Strontia (SrO) and Baryta (Bao).
This made the elements as alkaline earth metals. They have two electrons in their valence shell and have a configuration of ns2. Radium is the radioactive member, though it possess similar properties like its group members. They are also electropositve in nature and have low first and second ionization energies. These elements are metals with distinctive luster when freshly cut.
In the flame tests, they give the following colors
P- block elements form the other end of the periodic table separated from the 's' block by the transition elements. There are six groups in the p- block elements, the main group elements. They are
Noble gases - Elements of 18th group
XeOF4 + 2H2O --> 4HF + XeO2Only one fluoride, krypton tetra fluoride is known. They are less stable than the Xenon fluorides.
|More topics in Main Group Elements|
|S-block Elements||P-block Elements|
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