How have the elements of the periodic table been created?

Question

and what hold them as such unique structures of mass

Answer 1

In Ancient Greece, the influential Greek philosopher Aristotle proposed that there were four main elements: air, fire, earth and water. All of these elements could be reacted to create another one; e.g., earth and fire combined to form lava. However, this theory was dismissed when the real chemical elements started being discovered. Scientists needed an easily accessible, well organized database with which information about the elements could be recorded and accessed. This was to be known as the periodic table.

The original table was created before the discovery of subatomic particles or the formulation of current quantum mechanical theories of atomic structure. If one orders the elements by atomic mass, and then plots certain other properties against atomic mass, one sees an undulation or periodicity to these properties as a function of atomic mass. The first to recognize these regularities was the German chemist Johann Wolfgang Döbereiner who, in 1829, noticed a number of triads of similar elements:

Some triads Element Molar mass
(g/mol) Density
(g/cm³)
chlorine 35.453 0.0032
bromine 79.904 3.1028
iodine 126.90447 4.933

calcium 40.078 1.55
strontium 87.62 2.54
barium 137.327 3.594
In 1829 Döbereiner proposed the Law of Triads: The middle element in the triad had atomic weight that was the average of the other two members. The densities of some triads followed a similar pattern. Soon other scientists found chemical relationships extended beyond triads. Fluorine was added to Cl/Br/I group; sulfur, oxygen, selenium and tellurium were grouped into a family; nitrogen, phosphorus, arsenic, antimony, and bismuth were classified as another group.

This was followed by the English chemist John Newlands, who noticed in 1865 that when placed in order of increasing atomic weight, elements of similar physical and chemical properties recurred at intervals of eight, which he likened to the octaves of music, though his law of octaves was ridiculed by his contemporaries.[2] However, while successful for some elements, Newlands' law of octaves failed for two reasons:

It was not valid for elements that had atomic masses higher than Ca.
When further elements were discovered, such as the noble gases (He, Ne, Ar), they could not be accommodated in his table.
Finally, in 1869 the Russian chemistry professor Dmitri Ivanovich Mendeleev and four months later the German Julius Lothar Meyer independently developed the first periodic table, arranging the elements by mass. However, Mendeleev plotted a few elements out of strict mass sequence in order to make a better match to the properties of their neighbors in the table, corrected mistakes in the values of several atomic masses, and predicted the existence and properties of a few new elements in the empty cells of his table. Mendeleev was later vindicated by the discovery of the electronic structure of the elements in the late 19th and early 20th century.

Earlier attempts to list the elements to show the relationships between them (for example by Newlands) had usually involved putting them in order of atomic mass. Mendeleev's key insight in devising the periodic table was to lay out the elements to illustrate recurring ("periodic") chemical properties (even if this meant some of them were not in mass order), and to leave gaps for "missing" elements. Mendeleev used his table to predict the properties of these "missing elements", and many of them were indeed discovered and fit the predictions well.

With the development of theories of atomic structure (for instance by Henry Moseley) it became apparent that Mendeleev had listed the elements in order of increasing atomic number (i.e. the net amount of positive charge on the atomic nucleus). This sequence is nearly identical to that resulting from ascending atomic mass.

In order to illustrate recurring properties, Mendeleev began new rows in his table so that elements with similar properties fell into the same vertical columns ("groups").

With the development of modern quantum mechanical theories of electron configuration within atoms, it became apparent that each horizontal row ("period") in the table corresponded to the filling of a quantum shell of electrons. In Mendeleev's original table, each period was the same length. Modern tables have progressively longer periods further down the table, and group the elements into s-, p-, d- and f-blocks to reflect our understanding of their electron configuration.

In the 1940s Glenn T. Seaborg identified the transuranic lanthanides and the actinides, which may be placed within the table, or below (as shown above).

Answer 2

For this discussion, assume the elements are electrically neutral (same number of electrons and protons). To get the mass, we add the number of protons and neutrons. A proton and an electron weighs the same amount as a neutron. Protons repel each other because they have the same electrical charge. Adding neutrons provides a force that will attract the neutrons and protons and hold the nucleus together. Too few or too many neutrons and the nucleus becomes unstable.

The order of the elements is based on the number of electrons in the outer shell of the atoms. The first shell only has room for two electrons. This gives us hydrogen (one electron and one proton) and helium (two electrons and two protons). When the first shell is full, electrons go into the second shell, which has room for eight electrons. When the second shell is full, the third starts filling.

Atoms with the same number of electrons in the outer shell behave similarly, but the lighter elements are more aggressive chemically, so they will replace the heavier ones in a molecule. For example, if you have potassium chloride in a solution and add sodium, you will get sodium chloride and potassium because sodium is lighter (one fewer electron shells).

Answer 3

The elements were created when the big bang happened. Hydrogen (in the explosion) nuclei fused together due to the immense heat to form new elements. This is called nuclear fusion/fission (see sources).

The thing that holds them as such unique structures of mass is the charge of the neutrons and protons in the nucleus, and how much protons there is in the atoms of the element. This positive and negative charge means that the atoms are attracted to other atoms of certain types, or repelled by them. This is why you can never force two atoms together that don't attract, meaning that you can never change the atom arrangement of the unique structure of the element itself. Also, you can't change the number of protons in an element, so you can't change it in that way either.

Answer 4

Only some have been created by people, most were discovered. Among those discovered, it is assumed that most of the heavy ones were created from lighter ones in a fusion process in stars that went nova in the early years of the universe. There are over 100 so dimensioning all of them would be tedious and take a semester of chemistry.
The unique structure of elements is the result of each having a specific number of protons and neutrons. As we go up in counting the number of protons we get specific slots in the periodic table - knock out a proton and we get a new element. The basis for atomic physics, another semester of classes.

Answer 5

In chemistry and physics, the atomic number (also known as the proton number) is the number of protons found in the nucleus of an atom, so all the periodic table is is a list of known atoms, showing the number of protons.
As to what defines the structure, thats a minefield! Simplistically its the bonds between the atoms constituents that define its shape. Different parts have different lengths and attractive qualities.

Answer 6

Hahaha loved both definitions of these elements. your on a roll tonight my friend thx for the laugh star

Answer 7

well most of the elements are not manmade they are natural and the ones that are manmade usually only last for like a minute.

Answer 8

by nuclear reactions, in the beginning they was only hydrogen stars then formed helium when they "burn" and when they went supernova they formed the other elements.