You are not the first to wonder about that. Fred Hoyle did so with considerable success. Except that very few of the various isotopes of nuclei hanging around are actually formed on earth, but rather in primordial nucleosynthesis or during later stellar processes.

Why is every element formed this way? Maybe because everything which is not explicitly forbidden in nature is mandatory :=D. A more challenging, and perhaps rewarding, question is to explain the relative amount of the various nuclides. This has been used to constrain theories for cosmological evolution.

http://physicsworld.com/cws/article/news/2013/jan/03/carbons-hoyle-state-calculated-at-long-last

Dear Kare Olaussen, thank you for your answer. It seems few elements are not naturally available and they have been artificially prepared in laboratories. I again thank those scientists who with their patient research works have invented these elements.Can you please explain, the industrial use of these artificial elements in commercial scale? Even though these are not useful for human race,we are proud of our great scientists for their continued effort and have come out with flying colors.

Each element has several isotopes. Most of them do not live long, others are stable. 

Some isotopes are being constantly produced on Earth by cosmic rays. Some other unstable isotopes are ancient, remnants of the stars from which the Earth's material came. They are decaying constantly, and in future there will be none left.

The most prominent use of the artificial elements is the production of Plutonium in the breeder for nuclear reactors or for nuclear weapons. Short-lived isotopes can be used as radioactive markers. 

The basic question asked by Sh Muduli is very simple. Once the concept of periodicity is understood the answer to the question put by Sh Muduli can be easily evolved. This basic understanding does not require an expert with Ph.D. degree in chemistry as mentioned by Sh Muduli. The periodicity refers to trends or recurring variations in element properties with increasing atomic number. Periodicity is caused by regular and predictable variations in element atomic structure. Mendeleev organized elements according to recurring properties to make a periodic table of elements. Elements within a group (column) display similar characteristics. The rows in the periodic table (the periods) reflect the filling of electrons shells around the nucleus, so when a new row begins, the elements stack on top of each other with similar properties. For example, helium and neon are both fairly unreactive gases that glow when an electric current is passed through them. Lithium and sodium both have a +1 oxidation state and are reactive, shiny metals. 

Periodicity was helpful to Mendeleev because it showed him gaps in his periodic table where elements should be. This helped scientists find new elements, because they could be expected to display certain characteristics based on the location they would take in the periodic table. Now that the elements have been discovered, scientists and students used periodicity to make predictions about how elements will behave in chemical reactions and their physical properties. Periodicity helps chemists to predict how the new, superheavy elements might look and behave. Hence before the discovery of any element its periodic properties have already been predicted. Once the new element suits to those properties it occupies the particular position in periodic table.

Dear P.Sahoo Sir,

                 Your concept on periodicity to fill up the vacant place in periodic table is quite logical and understood, but my question centres round the idea that as natural numbers are man made,they came/designed in serial, but all these elements which form under certain fixed environmental and natural conditions dependant may not be available on the earth as it is designed in periodic table.The prevailing environmental conditions may not be favourable/suitable for few elements to form as it is seen in periodic table.  

Radhashyam> The prevailing environmental conditions may not be favourable/suitable for few elements to form as it is seen in periodic table.

You are right. The "periodic" table (which is not really periodic, but reveals a predictable repeated pattern) is governed by atomic physics (electromagnetism and quantum mechanics); i.e. of how Z electrons can bind to a charge-Z nucleus (if it exist). Mendeleev was perhaps lucky that nuclei with all charges from Z=1 (hydrogen) to Z=92 (uranium) can be found on earth. This is determined by nuclear physics; it is not obvious that all values of Z should occur as stable entities.

Actually, element 91 (protactinium) was missing for a very long time. Probably because there is no stable isotope of it; the least unstable one (Pa 231) has a lifetime of 3.276 x 104 years. So there goes your connection between Nature and the Natural Numbers! After uranium, you have to go to very big chunks of nuclear matter (in the form of gravitationally bound neutron stars) to regain stability.

Actually, almost every nuclide is only metastable; when a single nucleus cannot divide into smaller pieces with release of (kinetic) energy, as in fission and alpha-decay (or undergo beta-decay/electron-capture), it will not change in a normal earthly environment. But by cooking baryonic matter in stars for sufficiently long time, and cooling down very carefully, it should all end up as Iron-56, which is the isotope with lowest mass per baryon. Unless all baryonic matter disappear through proton decay, as predicted by some theories of elementary particle physics...

Note added: See the post by Gamlet below for a more accurate description of which elements are stable (in an earthly environment). So Mendeleev was perhaps not as lucky as I thought.

There are now 118 discovered elements (not 117). The last, 118th is Oganesson (Og) - an inertial gas. Elements from 1 (Hydrogen H) till 82 (Plumbum Pb) have stable isotops except 43 (Technecium Tc) and 61 (Prometium Pm) and were found on Earth and Sun (Helium He) with som unstable but long living elements (from Bi to Uranium). Elements from 93 Neptunium till 98 Californium (as well as 43 and 61) are created in nuclear reactors. Some higher elements are found as a result of nuclear explosion. The ultra high elements are created jn colliders.