![]() ![]() Point to Remember: Mostly for transition and inner transition elements, the valence electrons are the electrons present in the shells outside the noble gas core. The electron dots in the Lewis structure are a convenient way to determine how many bonds an atom of an element can make. 1: Lewis symbols or electron-dot symbols of the first twenty elements in the periodic table. Thus the inner transition elements have valence electrons ranging from 3 to 16 (See above image of periodic table). Helium is an exception that has only two valence electrons, but they are shown paired. ![]() So the electrons present in the f-orbitals as well as s-orbitals act like valence electrons. The inner transition elements have incomplete f-orbitals and the f-orbitals are very close to outer s-orbitals. The inner transition elements also have a similar case. Thus the transition elements have valence electrons ranging from 3 to 12 (See above image of periodic table). So the electrons present in the d-orbitals as well as s-orbitals act like valence electrons. The transition elements have incomplete d-orbitals and the d-orbitals are very close to the outer s-orbitals. It seems a little difficult to find the valence electrons of transition elements and inner transition elements. Valence electrons of Transition and Inner transition elements Now, this method does not suit for transition and inner transition elements. And the number of electrons present in this principal quantum number is 2. Most periodic tables provide additional data (such as atomic mass) in a box that contains each element’s symbol. A modern version is shown in Figure 4.9.1 4.9. These variables allowed Mendeleev to place each element in a certain row (called a period) and column (called a group). The periodic table is one of the cornerstones of chemistry because it organizes all the known elements on the basis of their chemical properties. In this electron configuration, you can see that the highest principal quantum number is 3. The chemical properties of elements is determined primarily by the number and distribution of valence electrons. The periodic table is arranged by atomic weight and valence electrons. The electron configuration of magnesium is 1s 2 2s 2 2p 6 3s 2. Let’s consider the example of magnesium only. In the electron configuration, you have to see the total number of electrons present in the shell with a highest principal quantum number. You can also find the valence electrons by using the electron configuration of elements. So the valence electrons of magnesium are 2. You can see that the magnesium atom has 2 electrons in its outermost orbit.
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