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Alkali metals Со mpleted : Kabylkakov Amirzhan Checked: Alexey Nikolaevish

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Position in the periodic table of chemical elements : • Alkali metals are located in the main subgroup of the first group of the periodic table of chemical elements D.I. Mendeleev. These are lithium Li, sodium Na, potassium K, cesium Cs, rubidium Rb and francium Fr.

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Electronic structure of alkali metals and basic properties : • Electronic configuration of the outer energy level of alkali metals: ns1, the outer energy level contains 1 s-electron. Therefore, the typical oxidation state of alkali metals in compounds is +1. • Let us consider some patterns of changes in the properties of alkali metals.

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• In the series Li-Na-K-Rb-Cs-Fr, in accordance with the Periodic Law, the atomic radius increases, metallic properties increase, non-metallic properties weaken, and electronegativity decreases.

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Physical properties : • All alkali metals are soft, silvery substances. Their freshly cut surface has a characteristic shine.

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• The crystal lattice of alkali metals in the solid state is metallic. Consequently, alkali metals have high thermal and electrical conductivity. They boil and melt at low temperatures. They also have low density.

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Qualitative reactions : • A qualitative reaction to alkali metals is the coloring of the flame with salts of alkali metals. • Flame color: • Li - carmine red • Na - yellow • K - purple • Rb - brown-red • Cs - violet-red

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Chemical properties : • 1. Alkali metals are strong reducing agents. Therefore, they react with almost all non-metals. • 1.1. Alkali metals readily react with halogens to form halides: 2K + I2 = 2KI • 1.2. Alkali metals react with sulfur to form sulfides: 2Na + S = Na2S • 1.3. Alkali metals react actively with phosphorus and hydrogen (very actively). In this case, binary compounds are formed - phosphides and hydrides: 3K + P = K3P 2Na + H2 = 2NaH • 1.4. Lithium reacts with nitrogen at room temperature to form nitride: 6Li + N2 = 2Li3N Other alkali metals react with nitrogen when heated.

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• 1.5. Alkali metals react with carbon to form carbides, mainly acetylenides: 2Na + 2C = Na2C2 • 1.6. When interacting with oxygen, each alkali metal exhibits its own individuality: when burning in air, lithium forms an oxide, sodium - mainly peroxide, potassium and other metals - superoxide. 4Li + O2 = 2Li2O 2Na + O2 = Na2O2 K + O2 = KO2

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• 2. Alkali metals actively interact with complex substances: • 2.1. Alkali metals react violently (explosively) with water. The interaction of alkali metals with water leads to the formation of alkali and hydrogen. Lithium reacts violently, but without explosion. For example, potassium reacts very violently with water: 2K0 + H2+O = 2K+OH + H20

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• 2.2. Alkali metals react explosively with mineral acids (hydrochloric, phosphoric and dilute sulfuric acid). This produces salt and hydrogen. For example, sodium reacts violently with hydrochloric acid: 2Na + 2HCl = 2NaCl + H2↑ • 2.3. When alkali metals react with concentrated sulfuric acid, hydrogen sulfide is released. For example, when sodium reacts with concentrated sulfuric acid, sodium sulfate, hydrogen sulfide and water are formed: 8Na + 5H2SO4(conc.) → 4Na2SO4 + H2S + 4H2O

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• 2.4. Alkali metals react with nitric acid. When reacting with concentrated nitric acid, nitric oxide (I) is formed: 8Na + 10HNO3 (conc) → N2O + 8NaNO3 + 5H2O With dilute nitric acid, molecular nitrogen is formed: 10Na + 12HNO3 (diluted)→ N2 +10NaNO3 + 6H2O When alkali metals react with very dilute nitric acid, ammonium nitrate is formed: 8Na + 10HNO3 = 8NaNO3 + NH4NO3 + 3H2O

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• 2.5. Alkali metals can react even with substances that exhibit very weak acidic properties. For example, with ammonia, acetylene, alcohols, phenol and organic acids. For example, when lithium reacts with ammonia, amides and hydrogen are formed: 2Li + 2NH3 = 2LiNH2 + H2 ↑ Acetylene with sodium forms sodium acetylenide and also hydrogen: H ─ C ≡ C ─ H + 2Na → Na ─ C≡C ─ Na + H2

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• Phenol reacts with sodium to form sodium phenolate and hydrogen: 2C6H5OH + 2Na → 2C6H5ONa + H2↑ • Methanol and sodium form sodium methoxide and hydrogen: 2CH3OH + 2Na → 2 CH3ONa + H2↑ • Acetic acid with lithium forms lithium acetate and hydrogen: 2 С H3COOH + 2Li → 2CH3COOLi + H2↑ • Alkali metals react with haloalkanes (Wurtz reaction). For example, chloromethane with sodium forms ethane and sodium chloride: 2CH3Cl + 2Na → C2H6 + 2NaCl

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• 2.6. In a melt, alkali metals can react with some salts. Note! In solution, alkali metals will react with water, and not with salts of other metals. For example, sodium reacts in a melt with aluminum chloride: 3Na + AlCl3 → 3NaCl + Al

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Sources used : • https://chemege.ru/alkalimetals/

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• Thank you for your attention !

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