GENERAL KNOWLEDGE

     ELEMENTS

An element is asubstance composed of only one type of atom.Elements are the most basic substances in the universe and cannot be split into anything simpler.There are 109 elements ,91 of which occur naturally ,ans 18 of which can be made artificially.All life on earth is based on the element carbon, which is vital to functioning of living cells.Oxygen is the most plentifull element on Earth.It occur in water, Air and even rocks.

       Groups of Elements

      Just as the members of a human family share the same characteristics,ther are ''families'' of elements that have similar properties.An elements chemical properties are determined by the structure of its attoms. Elements in same group have similar atomic structures.

 Alkali metals

The alkali metals make up Group 1 of the table, and comprise lithium (Li) through francium (Fr). These elements have very similar behavior and characteristics. Hydrogen is Group 1, but it exhibits few characteristics of a metal and is often categorized with the nonmetals.

      Alkaline earth metals

The alkaline earth metals make up Group 2 of the periodic table, from beryllium (Be) through radium (Ra). The alkaline earth metals have very high melting points and oxides that have basic alkaline solutions.

      Lanthanides

The lanthanides comprise elements 57 — lanthanum (La), hence the name of the set — through 71, lutetium (Lu). They, along with the actinides, are often called "the f-elements" because they have valence electrons in the f shell.

      Actinides

The actinides comprise elements 89, actinium (Ac), through 103, lawrencium (Lr). They, along with the lanthanides, are often called "the f-elements" because they have valence electrons in the f shell. Only thorium (Th) and uranium (U) occur naturally with significant abundance. They are all radioactive.

      Transition metals

The transition elements are metals that have a partially filled d subshell and comprise Groups 3 through 12 and the lanthanides and actinides.

      Post-transition metals 

The post-transition elements are aluminum (Al), gallium (Ga), indium (In), thallium (Tl), Tin (Sn), lead (Pb) and bismuth (Bi). As the name implies, these elements have some of the characteristics of the transition metals, but they tend to be softer and conduct more poorly than the transition metals.

      Metalloid

The metalloids are boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), tellurium (Te) and polonium (Po). They sometimes behave as semiconductors (B, Si, Ge) rather than as conductors. Metalloids are also called "semi-metals" or "poor metals."

      Nonmetals

The term "nonmetals" is used to classify Hydrogen(H), carbon (C), nitrogen (N), phosphorus (P), oxygen (O), sulfur (S) and selenium (Se).Halogens 

The halogen elements are a subset of the nonmetals. They comprise Group 17 of the periodic table, from fluorine (F) through astatine (At). They are generally very chemically reactive and are present in the environment as compounds rather than as pure elements.

      Noble gases

 The inert, or noble, gases comprise Group 18. They are generally very stable chemically and exhibit similar properties of being colorless and odorless.

       Artificial Elements 

New elements can be created by bombarding existing elements with high-speed subatomic particles in a device is called a partivle accelerator.since 1937, scientists have made 18 new elements,some of which only exist for a few millions of second.

       Elements in nature

Only a few of the naturally ocurring elements can be found in their pure state.Most elements combine ,or react,with other elements to form more complex substance called compounds.pure gold can be mined directly from the ground because it is unreactive, that is it does not readily form compounds.

orange color are the natural elements

       Dmitry Mendeleev
          

 Dmitry Mendeleev was a Russian chemist and inventor. He formulated the Periodic Law, created his own version of the periodic table ofelements, and used it to correct the properties of some already discovered elements and also to predict the properties of eight elements yet to be discovered.