How is the periodic table constructed? how did electrons shells hold their electrons and the giving (+) and taking of (-) electrons.

In the modern periodic table, the elements are listed in order of increasing atomic number. The atomic number is the number of protons in the nucleus of atoms. The elements are arranged according to the increasing atomic numbers in periodic table. Each horizontal row on the periodic table is called a period. There are seven periods on the periodic table. Elements in the same period all have the same electron ground state energy level. As you move from left to right across a period, elements transition from displaying metal characteristics . Each vertical column on the periodic table is called a group. Elements belonging to one of the 18 groups will share similar properties. Atoms of each element within a group have the same number of electrons in their outermost electron shell. 

Step-by-step explanation

Electrons shells hold their electrons and the giving (+) and taking of (-) electrons:

an electron shell may be thought of as an orbit followed by electrons around an atom's nucleus. The closest shell to the nucleus is called the 1 shell also called the K shell, followed by the 2 shell or L shell then the 3 shell or M shelland so on farther and farther from the nucleus. The shells correspond to the principal quantum numbers (n = 1, 2, 3, 4 ...)The first shell can hold up to two electrons, the second shell can hold up to eight (2 + 6) electrons, the third shell can hold up to 18 (2 + 6 + 10) and so on. The general formula is that the nth shell can in principle hold up to 2(n2)

Atoms and chemical species lose or gain electrons when they react in order to gain stability. Thus, metals (with nearly empty outer shells) lose electrons to non-metals, thereby forming positive . Gaining or losing electron is to acquire duplet or octet configuration which are stable configuration.