Here is a table representing the number of valence electrons of elements belonging to the second period and their electronic configuration. The periodic table shown above demonstrates how the configuration of each element was aligned so that the last orbital filled is the same except for the shell. So, just by writing the electronic configuration of that element, we can quickly determine its number of valence electrons. The configuration of electrons gives a quick overview of the number of electrons present in the last shell. The arrangement of electrons in such orbitals is known as electronic configuration. Within the shells, electrons occupy a special place called atomic orbitals. Count the number of valence electrons: How many valence electrons in Bi. By Using Electronic Configuration of the Element Get information about a chemical element. Answer: All have an ns2np5 electron configuration, one electron short of a noble gas electron configuration. Use the periodic table to predict the characteristic valence electron configuration of the halogens in group 17. The table below depicts the number of valence electrons in the different groups of the periodic table: Periodic Table GroupĢ. By extrapolation, we expect all the group 2 elements to have an ns2 electron configuration. The rule applies to the transition and inner transition elements in groups 3-12. However, this only holds for the main group elements, groups 1-2 and 13-18. In contrast, the number of valence electrons across a period increases by one as we move left to right of a period.Įxception: As discussed, the period number indicates the number of shells, whereas the group number specifies the valence electron number in the outermost shell of an atom. This similarity occurs because the members of a group have the same number and distribution of electrons in their valence shells. As we proceed downwards in a group, the numbers of valence electrons are same, although the number of shells increases. Here, we just refer to the periodic table and search for the position of the element in it. It is the most widely used method to determine the number of valence electrons in an element. There are two ways of calculating the number of valence electrons in an element.
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