Hydrogen may be produced from water using the process of electrolysis, but this process is significantly more expensive commercially than hydrogen production from natural gas. Elemental hydrogen is relatively rare on Earth, and is industrially produced from hydrocarbons such as methane, after which most elemental hydrogen is used "captively" (meaning locally at the production site), with the largest markets almost equally divided between fossil fuel upgrading, such as hydrocracking, and ammonia production, mostly for the fertilizer market. Stars in the main sequence are mainly composed of hydrogen in its plasma state. Hydrogen is the most abundant of the chemical elements, constituting roughly 75% of the universe's elemental mass. With an atomic mass of 1.00794 amu, hydrogen is the lightest element. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H 2. Hydrogen (H) is the chemical element with atomic number 1. This trend states that the first element of each group often behaves quite differently from the succeeding ones: the difference is largest in the s-block (H and He), is moderate for the p-block (B to Ne), and is less pronounced for the d- and f-blocks. The valence shell lacks "p" or any other kind of orbitals due to the general l > p > d > f). The first electron shell, n = 1, consists of only one orbital, and the maximum number of valence electrons that a period 1 element can accommodate is two, both in the 1s orbital.
Position of period 1 elements in the periodic table In terms of vertical trends down groups, helium can be seen as a typical noble gas at the head of the IUPAC group 18, but as discussed below, hydrogen's chemistry is unique and it is not easily assigned to any group. However, period 1 contains only two elements, so this concept does not apply here. 2 Position of period 1 elements in the periodic tableĪll other periods in the periodic table contain at least eight elements, and it is often helpful to consider periodic trends across the period.
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