Elements, as they appear on the periodic table, have no net charge. They all have equal numbers of protons (+) and electrons (-). HOWEVER, an atom can gain or lose electrons, which will change its charge, but, again, on the periodic table, they all have 0 charge.
Elements listed in the periodic table of elements are neutral; they do not have a charge. When they undergo chemical reactions they may become charged ions. There is no single most common charge for ions, but the most common are -1, -2, -3, +1, +2 and +3.
In the periodic table, an element's atomic number indicates the number of protons in its nucleus. If the number of electrons in its orbit is known, its ionic charge can be easily determined by subtracting the number of electrons from the atomic number.
No. The position of an element in the periodic table cannot predict the number of isotopes it has. However, the position of an element in the periodic table can predict other properties like the charge of its ion, the formula of its oxide, the acidic or basic nature of its oxide, etc.
If they're in the same group (vertical column) on the periodic table, then they will have the same charge. It's based on how many valence electrons they have. The periodic table is organized this way to make it easy to predict things like reactivity.