The positioning of hydrogen in periodic table, as an element of Group I (Alkali metals) is somewhat contentious. This is because, hydrogen shares some similarities with elements of Group I, IV-A and VII-A. It also exhibits different behavior than elements of all these groups.
Group IV-A (also known as Group 14) consists of carbon, silicon, germanium, tin, lead, etc. These elements share certain characteristics with hydrogen. Like hydrogen, all these elements have half filled valence shells. Hydrogen has an atomic number of 1 and its electronic configuration is `1s^1` . Similarly, carbon has an atomic number of 6 and an electronic configuration of `1s^2, 2s^2, 2p^2` . When comparing the electronegativity, hydrogen and members of group IV A have similar values. The electronegativity of hydrogen is 2.2 and carbon is 2.55, etc. The electron affinity of hydrogen and carbon are also comparable. The ionization potential of hydrogen is 13.6, while that of carbon is 11.3.
Thus, hydrogen and members of group IV-A of the periodic table share some common characteristics.
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