![]() ![]() Hydrogen resembles alkali metals in its electronic configuration. Hydrogen has an electronic configuration of 1s¹ so by rule, it has to be placed at the first position. In some tables, it is placed lonely at the top, and in some other tables, it is placed with alkali metals. In the periodic table, hydrogen does not have a fixed position. Position of Hydrogen in the Periodic Table This is why hydrogen ions do not exist freely in nature. This size is much smaller than the atomic size of many metals. When an electron is lost from a hydrogen atom, its nucleus size reduces to about 1.5 × 10 -3 pm. That is why special attention is for hydrogen’s position in the periodic table. Hydrogen exists as a diatomic molecule that is similar to halogens like chlorine.Įven if the hydrogen is similar to both alkali metals and halogens, both of them are different. For example, the ionization enthalpy of lithium is 520 kJ mol-1 and that for fluorine is 1680 kJ per mol and lastly that for hydrogen is 1312 kJ per mol. In terms of ionization enthalpy, hydrogen is more similar to halogens in comparison to alkali metals. Different from alkali metals, hydrogen has very high ionization enthalpy due to which it lacks metallic characters in normal conditions. And when an electron is lost, a cation is produced and hydrogen resembles alkali metals.Ĭoming to the formation of compounds, hydrogen can produce sulfides, oxides, and halides as other alkali metals. When one electron is gained hydrogen becomes a uni-negative ion, which is similar to hydrogens. Hydrogen has one electron less required for completion of electron octet in its shell. This structure is the same as that of halogens (ns 2, np 5). Hydrogen can have a noble gas configuration structure and have a similar structure as helium by accepting an electron. Therefore the electronegativity is greatest at the top-right of the periodic table and decreases toward the bottom-left.The structure of hydrogen is similar to that of alkali metals (ns¹) that have 1 electron in their outermost shell. Elements with high ionization energies have high electronegativities due to the strong pull exerted by the positive nucleus on the negative electrons. Electrons with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on electrons. Electronegativity is related with ionization energy and electron affinity. The most electronegative atom, fluorine, is assigned a value of 4.0, and values range down to cesium and francium which are the least electronegative at 0.7. The higher the associated electronegativity number, the more an element or compound attracts electrons towards it. In general, an atom’s electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The electronegativity of Hydrogen is: χ = 2.2 ![]() For this purposes, a dimensionless quantity the Pauling scale, symbol χ, is the most commonly used. Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom to attract electrons towards this atom. ![]()
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