How does the electron configuration of an atom change when it gains or loses an electron to become an ion? The answer to this important question depends on the location of the atom in the Periodic Table. By extrapolation, we expect all the group 2 elements to have an ns 2 electron configuration. The next element down, magnesium, is expected to have exactly the same arrangement of electrons in the n = 3 principal shell: 3 s 2. Beginning with beryllium, we see that its nearest preceding noble gas is helium and that the principal quantum number of its valence shell is n = 2.ī Thus beryllium has an 2 s 2 electron configuration. Write the valence electron configuration of each element by first indicating the filled inner shells using the symbol for the nearest preceding noble gas and then listing the principal quantum number of its valence shell, its valence orbitals, and the number of valence electrons in each orbital as superscripts.Ī The group 2 elements are in the s block of the periodic table, and as group 2 elements, they all have two valence electrons.Locate the nearest noble gas preceding each element and identify the principal quantum number of the valence shell of each element. Identify the block in the periodic table to which the group 2 elements belong.Use the periodic table to predict the valence electron configuration of all the elements of group 2 (beryllium, magnesium, calcium, strontium, barium, and radium).Īsked for: valence electron configurations For elements after No, the electron configurations are tentative. The electron configurations of the elements indicated in blue are also anomalous, but the reasons for the observed configurations are more complex. The electron configurations of elements indicated in red are exceptions due to the added stability associated with half-filled and filled subshells. Figure 2.3.2 Electron Configurations of the Elements. Although helium, with a filled ns subshell, should be similar chemically to other elements with an ns 2 electron configuration, the closed principal shell dominates its chemistry, justifying its placement above neon on the right. Although hydrogen is not an alkali metal, its 1 s 1 electron configuration suggests a similarity to lithium (2 s 1) and the other elements in the first column. Hydrogen and helium are placed somewhat arbitrarily. Figure 2.3.2.īecause each orbital can have a maximum of 2 electrons, there are 2 columns in the s block, 6 columns in the p block, 10 columns in the d block, and 14 columns in the f block. As you will see, this is reflected in important similarities in the chemical reactivity and the bonding for the elements in each column. Within each column, each element has the same valence electron configuration-for example, ns 1 (group 1) or ns 2 np 1 (group 13). At the bottom lie the 14 columns of the f block, elements in which the ( n − 2) f orbitals are filled.īecause two electrons can be accommodated per orbital, the number of columns in each block is the same as the maximum electron capacity of the subshell: 2 for ns, 6 for np, 10 for ( n − 1) d, and 14 for ( n − 2) f. In between are the 10 columns of the d block, elements in which the ( n − 1) d orbitals are filled. The six columns on the right, elements in which the np orbitals are being filled, constitute the p block. As a result, the periodic table can be divided into “blocks” corresponding to the type of subshell that is being filled, as illustrated in Figure 2.3.1.įor example, the two columns on the left, known as the s block, consist of elements in which the ns orbitals are being filled. Although the table was originally organized on the basis of physical and chemical similarities between the elements within groups, these similarities are ultimately attributable to orbital energy levels and the Pauli principle, which cause the individual subshells to be filled in a particular order. Atomic no.\)Īs you have learned, the electron configurations of the elements explain the otherwise peculiar shape of the periodic table. The Shorthand electron configuration (or Noble gas configuration) as well as Full electron configuration is also mentioned in the table. Electron configuration chart of all Elements is mentioned in the table below.
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