30. ALKALI METALS.

Elements of the first group, the main subgroup belong to alkali metals: lithium, sodium, potassium, rubidium, caesium, francium.

STAY IN THE NATURE

% Na-2,64 (on weight), % K-2,5 (on weight), Li, Rb, is Cs-much less, Fr-artificially received element NaCl - sodium chloride (rock salt), halite Na2SO4 · 10H2O - glauber salt NaNO3 - nitratine Na3AlF6 - cryolite Na2B4O7 · 10H2O - borax KCl - sylvite KCl · NaCl - sylvinite

Properties of alkali metals.

Element	Lithium Li	Sodium Na	Potassium K	Rubidium Rb	Caesium Cs
Property
Order number of element	3	11	19	37	55
Relative atomic mass	6,941	22,990	39,098	85,468	132,905
Temperature of melting, C0	179,0	97,8	63,5	39,0	28,5
Temperature of boiling, C0	1340	883	760	696	708
G/cm3 density	0,534	0,97	0,86	1,532	1,87
Oxidation levels	+1	+1	+1	+1	+1
Coloring of flame	dark red	yellow	blue-violet	blue-violet	blue-violet
Primeneiye of metals	bearing alloys, catalyst	gas-discharge lamps, the heat carrier in nuclear reactors	-	the scientific researcher - ские works	photo cells

RECEIVING

Since alkali metals are the strongest reducers, they can be recovered from connections only at electrolysis of fusions of salts: 2NaCl=2Na+Cl2 on katode:na ++ e=Na on anode:2cl - e=Cl2

 

CHEMICAL PROPERTIES
1. With oxygen (Rb, Cs - self-ignite)	2Na+O2=Na2O2; 2K+2O2=K2O4 (peroxides) 4Li+O2=2Li2O (lithium oxide)
2. With halogens	2Na+Cl2=2NaCl
3. With sulfur when heating	2Li+S=Li2S (sulfide)
4. Lithium interacts with nitrogen	6Li+N2=2Li3N (nitride)
5. With hydrogen when heating	2Na+H2=2NaH (hydride)
6. With water	2Na+2H2O=2NaOH+H2

 

COMPOUNDS OF ALKALI METALS Alkali metals - the strongest reducers, their ions do not show oxidizing properties
Hydroxides (caustic alkalis) - solid crystal matters, typically ionic connections, the strong bases. NaOH-caustic soda, the caustic soda KOH caustic heat Receiving: 1. Electrolysis of NaCl aqueous solution: cathode: H2O+2e=H2+2OH- anode: 2Cl - 2e=Cl2 overall reaction: 2H2O+2NaCl=2NaOH+Cl2+H2	Salts - typically ionic connections, as govern-are well rastvorima in water, except some salts of lithium. Formed by weak acids strongly are hydrolyzed. Na2CO3 10H2O - soda crystals Na2CO3 - soda ash NaHCO3 - baking soda K2CO3 - potash Receiving soda: 1. Ammoniac way - NaCl solution saturation by CO2 and NH3 gases NH3+CO2+H2O=NH4HCO3 NH4HCO3 +NaCl=NaHCO3+NH4Cl NaHCO3 drops out in deposit (we will a little dissolve) 2. Calcination - calcinating: NaHCO3=Na2CO3+CO2+H2O	Qualitative tests: coloring of flame ions Li + - dark red Na + - yellow K + - violet

  

 

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