3.5.2. Groupwise Electronic Configurations

Elements in the same vertical column or group have similar valence shell electronic configurations, the same number of electrons in the outer orbitals, and similar properties. For example, the Group 1 elements (alkali metals) all have ns1 valence shell electronic configuration as shown below.

This chunk explains that elements within the same group of the periodic table exhibit similar chemical properties due to their shared electronic configuration, specifically in their outermost shell. The notation 'ns1' signifies that these elements have one electron in their outer 's' orbital. This similarity is crucial because it defines how these elements react chemically. For instance, all the alkali metals in Group 1, such as lithium and sodium, easily lose that one outer electron, leading to similar reactivity traits.

Think of a group of people who all wear similar clothing styles. Just as their similar styles can suggest that they may enjoy similar activities, the similar electronic configurations in a group suggest that these elements will undergo similar chemical reactions.

We can classify the elements into four blocks viz., s-block, p-block, d-block and f-block depending on the type of atomic orbitals that are being filled with electrons.

This chunk introduces the classification of elements into different blocks on the periodic table based on their electronic configurations. The classification depends on the type of orbital being filled - 's', 'p', 'd', or 'f'. For example, elements in the s-block have their outermost electrons filling 's' orbitals and generally include alkali and alkaline earth metals. Understanding these blocks helps in predicting the properties of the elements, as elements in the same block often share similar characteristics and reactivity.

Imagine different sections in a library labeled by genres—fiction, non-fiction, biographies, etc. Just as books in the same section share a common theme or subject matter, elements in the same block on the periodic table share characteristics influenced by the type of orbital being filled.

We notice two exceptions to this categorisation. Strictly, helium belongs to the s-block but its positioning in the p-block along with other group 18 elements is justified because it has a completely filled valence shell (1s2) and as a result, exhibits properties characteristic of other noble gases.

This chunk highlights exceptions in the classification based on electronic configuration, specifically with helium and hydrogen. Although helium has an 's' orbital configuration (1s2), it is placed in the p-block among noble gases because it exhibits similar properties, such as a full valence shell and non-reactivity. This demonstrates that while electronic configuration is crucial, group placement also considers chemical behavior.

Consider a prestigious club where entry is based on specific criteria. Although someone might technically fit one category (like helium in the s-block), their behavior and characteristics might align better with another group (the noble gases), allowing them to be accepted there instead.

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