Nitrogen has 5 valence electrons; it needs 3 more to complete the octet. It shares three electrons with three hydrogen atoms, forming three covalent bonds. Therefore, valency is 3. In the case of nitrogen, covalency is 3, while its electrovalency could be 5 (losing all 5). For covalent molecules, valency = number of shared electron pairs. In N₂, valency is also 3 (triple bond).
Explanation:
Stainless steel contains iron, chromium (min 10.5%), and often nickel. Chromium forms a passive oxide layer preventing rust. Nickel improves ductility and corrosion resistance. Molybdenum may be added for pitting resistance. Brass is Cu-Zn, bronze is Cu-Sn, solder is Pb-Sn.
Explanation:
Reactivity series order: Na > Zn > Fe > Cu. Sodium (alkali metal) is extremely reactive, reacting violently with water. Copper is low in the series, hence used for water pipes.
Explanation:
Across a period, the atomic radius decreases. This is because the number of protons (nuclear charge) increases, pulling the electrons in the same shell closer to the nucleus, while the number of shells remains constant. This increases the effective nuclear charge experienced by the valence electrons.
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