describe how elements are organized right into the periodic table. Explain how some attributes of aspects relate to your positions top top the regular table.

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In the 19th century, many previously unknown elements were discovered, and scientists noted that particular sets of facets had similar yellowcomic.comical properties. For example, chlorine, bromine, and also iodine react v other elements (such as sodium) to make similar compounds. Likewise, lithium, sodium, and potassium react v other aspects (such as oxygen) come make similar compounds. Why is this so?

In 1864, Julius Lothar Meyer, a German yellowcomic.comist, organized the aspects by atomic mass and also grouped them follow to their yellowcomic.comical properties. Later that decade, Dmitri Mendeleev, a Russian yellowcomic.comist, organized all the known elements according to comparable properties. That left gaps in his table because that what he believed were undiscovered elements, and also he made part bold predictions about the nature of those undiscovered elements. When aspects were later found whose properties carefully matched Mendeleev’s predictions, his version of the table obtained favor in the scientific community. Because specific properties the the elements repeat on a continuous basis transparent the table (that is, they space periodic), it came to be known together the regular table.

Mendeleev had to perform some facets out that the bespeak of their atomic masses to team them v other elements that had comparable properties.

The regular table is among the cornerstones the yellowcomic.comistry due to the fact that it organizes all the known facets on the communication of your yellowcomic.comical properties. A modern-day version is displayed in figure \$$\\PageIndex1\$$. Most periodic tables provide added data (such together atomic mass) in a box that consists of each element’s symbol. The facets are listed in order of atomic number.

api/deki/files/259870/clipboard_e78a1746cfda9dd306537c497c2e2ad50.png?revision=1\" />Figure \$$\\PageIndex2\$$: species of Elements. Facets are either metals, nonmetals, or semimetals. Each team is situated in a different part of the periodic table.

Exercise \$$\\PageIndex1\$$

Based on its location in the periodic table, perform you mean indium (In) to be a nonmetal, a metal, or a semimetal?

Answer

metal

### Representative, shift and Inner-transition

Another way to categorize the facets of the periodic table is displayed in figure \$$\\PageIndex3\$$. The an initial two columns ~ above the left and also the last six columns ~ above the appropriate are dubbed the main group or representative elements. The ten-column block between these columns contains the transition metals. The two rows in ~ the main body that the periodic table contain the inner shift metals. The facets in these two rows are also referred to as, respectively, the lanthanide metals and the actinide metals.

Exercise \$$\\PageIndex1\$$

Using the change n to stand for the number of the valence electron shell, create the valence covering electron construction for every group.

the halogens the shaft of aspects headed by oxygen Answer a

The halogens space in the 17th column (or team 7A) that the regular table. This column synchronizes to the ns subshell gift filled v 5 electrons. Therefore, the valence covering electron configuration is ns2np5.

Answer b

The pillar headed through O is the 16th obelisk (or team 6A). This column synchronizes to the p subshell being filled through 4 electrons. Therefore, the valence covering electron configuration is ns2np4.

## Atomic Radius

The periodic table is valuable for knowledge atomic nature that present periodic trends. One such residential or commercial property is the atom radius (Figure \$$\\PageIndex5\$$). The atom radius is characterized as one-half the distance between the nuclei of identical atoms that are bonded together. The devices for atomic radii room picometers, same to \$$10^-12\$$ meters. Together an example, the internuclear distance in between the two hydrogen atom in an \$$\\ceH_2\$$ molecule is measured to it is in \$$74 \\: \\textpm\$$. Therefore, the atom radius the a hydrogen atom is \$$\\frac742 = 37 \\: \\textpm\$$.

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As discussed earlier, the greater the shell number, the farther from the nucleus the electron in that shell are likely to be. In other words, the size of an atom is generally figured out by the variety of the valence electron shell. Therefore, together we go under a shaft on the regular table, the atom radius increases. As we go across a period on the periodic table, however, electrons space being added to the same valence shell; meanwhile, more protons space being added to the nucleus, therefore the positive charge of the cell nucleus is increasing. The raising positive fee attracts the electrons more strongly, pulling them closer to the nucleus. Consequently, together we go throughout a period, from left to right, the atomic radius decreases. This trends room seen plainly in figure \$$\\PageIndex5\$$

Figure \$$\\PageIndex5\$$ fads on the routine Table. Atomic radii of the representative elements measured in picometers. The relative sizes the the atoms show several trends with regard come the structure of the regular table. Atoms come to be larger going down a group and going from appropriate to left throughout a period.