<span>There is a direct correlation between the period number and the energy level for valence electrons. For example, the H and He elements, in period 1, have their outer electrons in the energy level "1". This continues down the rows: all the elements in period 2 have their principal energy level as n = 2, period 3 has n = 3, and so on.</span>
<u>Halogens are reactive because:</u>
They have high electronegativity and also high nuclear charge. So, they are reactive and also gain an electron when they react with other elements.
Since they are very reactive, halogens are very harmful to living organisms. Some of the halogens are fluorine, chlorine, bromine, iodine, astatine. These are mostly non metals. Fluorine is one of the most reactive gas and also very toxic gas. When Fluorine reacts with glass along with small amounts of water, it forms silicon tetra fluoride (SiF4). Hence fluorine should be handled with substances like the inert organofluorine compound Teflon.
The cis and Trans-forms of hyponitrous acid are given below in the attached document.
Hyponitrous acid has the chemical formula H2N2O2 or HON=NOH. 62.028 g/mol is the molecular weight of it. Additionally, it can take either a trans or cis form. When dry, the trans-hyponitrous acid crystallizes into white, explosive particles. Additionally, it has a half-life of 16 days at 25oC at a pH 1-3 in aqueous solution and is a weak acid (pKa1=7.21, pKa2=11.54). It decomposes into nitrous oxide and water. It is incorrect to think of N2O as the anhydride of H2N2O2. However, even though cis acid is unknown, we can still get its sodium salts.
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