When Mendeleyev elaborated his periodic table in the 1860’s [1] , he classified elements by their atomic weight and by columns containing elements with the same physical or valence properties [2] . The first parameter, the atomic weight, has been changed by Van den Broek who proposed to classify elements by their number of positive charges in the nucleus [3] . This periodic table classifies isotopes having the same positive charge, at the same place. This periodic table is today a reference even in chemistry [4] . Many variations of the periodic table exist, each trying to complete it for a specific purpose, but none gives indications of chemical bonds or of the location of electronic charges. Understanding bonds and charges positions could be very useful in chemistry, mainly when studying compounds structures or predicting chemical reactions.

The present article is an attempt at addressing this limitation with a specific periodic table for chemistry. In this table, elements are classified by their number of electrons and their electronic structure in compounds, including when bearing charges. This specific table is based on the even-odd and the isoelectronicity rules recently proposed [5] [6] [7] [8] [9] . The even-odd rule gives the number of covalent bonds an element can have and the isoelectronicity rule allows to know where and how to add a charge when an element of a compound is needed. The specific periodic table for chemistry presents elements very similarly to the classical periodic table, with elements in rows and columns, but it additionally includes electronic structures of atoms when bearing charges.

First, we briefly recall the rules used and presents the two first rows of the specific periodic table for chemistry. It describes features common to atoms within each cell as well as to neighboring cells. The difference between organic, semi-organic and inorganic elements is then detailed, linked to the number of electrons pairs in their shells. We end with a list of neutral and charged compounds compatible with the featured table. This list is composed of compounds with elements of the main group [10] [11] .

Compounds used to illustrate the use of the table are known to exist under standard conditions in liquid or gaseous phase [12] , i.e. far from extreme pressure and temperature. This evidently removes solid structures from our study [13] [14] .

To remain conform to the notation used in previous papers dealing with the even-odd rule, compounds are noted in capitals: NH3 is for neutral ammonia, NH4(+) is an ammonia cation and NH2(−) an ammonia anion [4] [5] [6] [7] [8] [9] .

As highlighted in previous articles, charged elements that follow the even-odd rule can only bear a single charge. Another criterion of the rule is that a connection between two elements of a compound can only be a single covalent bond [5] [6] [7] [8] [9] .

The even-odd rule offers a method to calculate the number of covalent bonds an element can have when part of a compound [7] . The maximum number of covalent bonds is obviously linked to the valence number since valence electrons are available for bonding. However, valence electrons are not always involved in bonds and those unbound remain in pairs. The number of bonds of an element in a compound may hence be smaller than expected.

The isoelectronicity rule allows an element in a compound to be replaced by an element of the nearest column in the classical periodic table [8] . This is possible first: when both elements have the same external electronic structure and second when multi-charged elements are excluded.

Table 1 lists the first two rows of a specific periodic table for chemistry with 8 elements of the main group [10] [11] , including specifics on organic, inorganic and semi-organic elements [15] .

In Table 1, charged and uncharged elements are placed in columns numbered from 0 to 8.