In addition, the total number of electron shells an atom has determines which period it belongs to. Element C is located in Period 5, the 1st position in 5s. This means that B has two valence electrons in 3s (3s 2). Element B is located in Period 3, the 2nd position in 3s-block. Here is a table representing the number of valence electrons of elements belonging to the second period and their electronic configuration. An element’s location in the periodic table is largely dependent on its electrons the number of valence shell electrons determines its group, and the type of orbital in which the valence electrons lie in determines the element’s block. This means that A has two valence electrons in 2s (2s 2) and five valence electrons in 2p (2p 5). So, just by writing the electronic configuration of that element, we can quickly determine its number of valence electrons. Generally, elements in Groups 1, 2, and 13 to 17 tend to react to form a closed shell with a noble gas electron configuration ending in ns2 np6. The configuration of electrons gives a quick overview of the number of electrons present in the last shell. Elements whose atoms have the same number of valence electrons are grouped together in the Periodic Table. That is, he organized the elements in groups according to their chemical characteristics. Mendeleev combined the order of atomic weight with common valences to organize the elements in a table. All of the other elements have a charge when they have eight electrons all to themselves. The arrangement of electrons in such orbitals is known as electronic configuration. The valence, in Mendeleevs understanding, was an indication of the ability of an element to combine with other elements. Only the noble gases (the elements on the right-most column of the periodic table) have zero charge with filled valence octets. Within the shells, electrons occupy a special place called atomic orbitals. By Using Electronic Configuration of the Element The table below depicts the number of valence electrons in the different groups of the periodic table: Periodic Table GroupĢ. 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. 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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