Test: Electronic Configurations of Elements and the Periodic Table - Chemistry MCQ

Every period ends with a noble gas, as the element at the end of the period is with the fully filled orbitals. The 4^th period has an outer shell as O i.e. n = 4. So the configuration is [Ar}4s²3d¹⁰4p⁶, that is Krypton.

When electrons are distribution into the orbitals of the atoms by following Aufbau’s principal, Hund’s rule maximum multiplicity and Pauli’s exclusive principle, the order they are filled is represented by the electronic configuration.

Group I elements are known as Alkali metals as they have a great ability to form strong bases i.e. alkalies. Alkalies are the strong bases with the ability to neutralize strong acids. They consists of Lithium(Li), Sodium(Na), Potassium(K), Rubidium(Rb), Cesium(Cs) and Francium(Fr).

Quantum numbers are responsible for an element’s position in the periodic table. For example, as we know the principal quantum number defines the main energy level i.e. shell. The last orbital principal quantum number is the periodic number of the element.

The atomic number of Boron is 5 and it contains two elements in the K-shell and three elements in the L-shell as well as 4 electrons in s-orbital and 1 electron and p-orbital. The element preceding Boron is beryllium and the element succeeding Boron is carbon.

Neon is made up of 10 electrons. As per Aufbau’s principle, orbitals with lower energy must be filled first and s-orbital can only accommodate 2 electrons while p can accommodate 6 electrons. So the electronic configuration of Neon is 1s²2s²2p⁶.

The d-block elements are called transition elements as the electrons are energetically filled. The exact meaning of transition elements is that elements have either partially or fully filled subshell or can actively cations by losing electrons.

In the 3d transition series, the have either partially or fully filled 3d orbitals. The 3d transition state starts from Scandium (Z = 21) having electronic configuration as 3s²3d¹ and ends with Zinc (Z = 30) whose electronic configuration is 3s²3d¹⁰.

Both the Lanthanoid series and the Actinoid series make up Inner transition elements, but they are not the same. The 4f elements are lanthanoids (Z = 57 to Z = 71) and 5f are actinides (Z = 89 to Z = 113).

Inner transition elements are f-block i.e. 4f and 5f. They include elements from 57 to 71 and 89 to 103. The 4f elements are lanthanoids (57 – 71) and 5f are actinides (89 – 113). Most of the actinides are radioactive.