Electronic Configuration- Halogen Group

The group 17 elements of the periodic table are made up of five chemically similar elements:

Halogen Group

Halogen Group

  • Fluorine

  • Chlorine

  • Bromine

  • Iodine

  • Astatine

The term halogen has been derived from the Greek language which means salt producers, as halo means ‘salts’ and genes mean ‘born’.  The elements of the halogen group are highly reactive, non-metallic elements. These elements exhibit a gradual successive change in the physical and chemical properties of the elements.

Electronic configuration can simply be defined as the arrangement of electrons of an atom in its orbitals. Studying the electronic configuration of an atom or a molecule helps one understand the trends in the physical and chemical properties of an element. The reactivity and types of bonds formed by an element can be determined by knowing the number of electrons in the outermost shell of the element. In order to understand the electronic configuration of elements the three important principles for assigning the electrons into orbitals should be understood. The principles are:

  • Pauli’s exclusion principle

  • Hund’s rule of maximum multiplicity

  • Aufbau principle

Pauli’s exclusion principle is based on the quantum numbers defined by Pauli. He stated that all the four quantum numbers of any two electrons in an atom can never be identical. According to Hund’s rule, electrons get paired up in an orbital only after all the sub-shells consist of at least one electron in it. As per Aufbau principle, electrons of an element fill the energy levels in an increasing order. The general electronic configuration of group 17 elements is ns2np5. The electronic configuration of the halogen group is as shown below:

Period Element Symbol Atomic Number Electronic Configuration
2 Fluorine Fl 9 [He]2s22p5
3 Chlorine Cl 17 [Ne]3s23p5
4 Bromine Br 35 [Ar]3d104s24p5
5 Iodine I 53 [Kr]4d105s25p5
6 Astatine At 85 [Xe]4f145d106s26p5

Hence, these elements consist of seven electrons in their outermost shell. Join BYJU’S to get your doubts clarified by our expert mentors.


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