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# Which is the first element of the periodic table $?$

Last updated date: 26th Mar 2023
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The modern periodic table consists of $118$ elements of which $94$ are naturally occurring, the rest are man-made. Hydrogen (H) is the first element of the periodic table with atomic number $1$ . Its atomic weight is 1.008 u and is the lightest element in the periodic table. It is a colourless, odourless, tasteless and inflammable diatomic gas that exists as ${H_2}$ in the atmosphere.
A hydrogen atom consists of a single proton in its nucleus and an electron in its outermost shell. It does not have any neutrons. The electronic configuration of H is $1{s^1}$ . Two hydrogen atoms share their outer electrons to form a covalent bond to attain a stable $1{s^2}$ configuration and exist as ${H_2}$ . The position of hydrogen in the periodic table is a matter of discussion. Due to its $n{s^1}$ configuration, it resembles the alkali metals. But, the ionisation energy is very high and comparable with the halogens. Like halogens, it is non-metal and accepts an electron to complete its valence shell. Considering many other factors like melting and boiling point, reactivity towards metals and non-metals , hydrogen is placed under Group $1$ and period $1$ of the periodic table.