Physical properties: Sodium is very soft and can be cut with a knife. After cutting the outer skin, you can see that sodium has a silver-white metallic luster, which will soon be oxidized and lose its luster. Sodium is a good conductor of heat and electricity, and potassium-sodium alloy (liquid state) is the thermal conductive agent of atomic piles. The density of sodium is 0.97g/cm3, which is smaller than water and denser than kerosene. The melting point of sodium is 97.81°C and the boiling point is 882.9°C. Sodium element also has good ductility. Chemical properties: The outermost shell of a sodium atom has only one electron, which can be easily lost. Therefore, the chemical properties of sodium are very active. When it is used as a reducing agent in a redox reaction with other substances, its valence rises from 0 to +1. Strong metallicity. Its ions have weak oxidizing properties. 1. The reaction between sodium and oxygen at room temperature: 4Na＋O2=2Na2O (white powder) When ignited: 2Na＋O2=Na2O2 (light yellow powder) ★When sodium is ignited in the air, it quickly melts into a shining small ball, emitting yellow color Flame produces sodium peroxide (Na2O2). Sodium peroxide is more stable than sodium oxide. Sodium oxide can be synthesized with oxygen to form sodium peroxide. The chemical equation is: 2Na2O+O2=2Na2O2. 2. Sodium can react directly with halogens, sulfur, phosphorus, hydrogen and other non-metals to generate corresponding Compounds (reacted at room temperature), such as 2Na+Cl2=2NaCl (releases a lot of heat and generates a lot of white smoke) 2Na+S=Na2S (sodium sulfide) (it will explode when grinding when sodium and sulfur combine) 2Na+Br2=2NaBr (Sodium bromide) (Sodium bromide can be used as a sedative) 3. Reaction of sodium and water. Add some water to the beaker, add a few drops of phenolphthalein solution, and then put a small piece of sodium into the water. For safety reasons, the beaker should be covered with a glass piece. The observed phenomena and conclusions drawn from the phenomena are: 1. Sodium floats on the water (sodium is less dense than water) 2. Sodium melts into a shiny ball (sodium reacts with water to release heat. The melting point of sodium Low) 3. Sodium swims around on the water surface (gas is generated). The reaction between sodium element and water 4. Makes a hissing sound (gas is generated and the reaction is violent) 5. The water with phenolphthalein test solution dropped in advance turns red ( Alkali is generated) Reaction equation 2Na + 2H2O = 2NaOH + H2↑★Sodium Because this reaction is violent and can cause hydrogen to burn, sodium fires cannot be extinguished with water. Dry sand must be used to extinguish the fire. Sodium has strong reducing properties and can displace metals from some molten metal halides. Since sodium reacts easily with water, sodium cannot be used to displace metals that follow sodium in the order of metal activity from their salt solutions. 4. Reaction of sodium and acid solution The reaction of sodium and acid solution involves the amount of sodium. If there is a small amount of sodium, it can only react with acid, such as the reaction of sodium and hydrochloric acid: 2Na+2HCl=2NaCl+H2↑ If there is excess sodium, priority is given React with acid, and then react with water in the acid solution. The equation is shown in 3. 5. Reaction of sodium and salt (1) Reaction with salt solution. Put sodium into the salt solution. The sodium will first react with the water in the solution to generate hydrogen. Sodium oxide will continue to react if it can react with salt.

For example, sodium is put into copper sulfate solution: 2Na+2H2O=2NaOH+H2↑ 2NaOH+CuSO4=Na2SO4+Cu(OH)2↓ (2) Reaction with molten salt Most of these reactions are displacement reactions, which are common in the metal smelting industry, such as 4Na+ TiCl4 (melted) = 4NaCl + Ti (condition is high temperature) Na + KCl = K + NaCl (condition is high temperature) ★The reaction of sodium and molten salt cannot prove the strength of metal activity 6. Sodium reacts with organic matter and sodium can also react with certain Some organic matter reactions, such as the reaction between sodium and ethanol: 2Na+2C2H5OH→2CH3CH2ONa+H2↑ (the products are hydrogen and sodium ethoxide) 7. Chemical equations related to sodium (1) and non-metallic elements: 2Na+H2=high temperature=2NaH 4Na+O2=2Na2O (white Solid) 2Na＋O2=ignited=Na2O2 (light yellow powder) ⑵With metal elements; does not react ⑶With water: 2Na＋2H2O＝2NaOH＋H2↑　⑷With acid: 2Na+2HCl=2NaCl+H2↑ ⑸With alkali; does not react (reacts with alkali solution )　⑹With salt; ①4Na+TiCl4=High temperature=4NaCl+Ti 6Na+2NaNo2=High temperature=N2↑+4Na2O Na+KCl=High temperature=K↑+NaCl ②2Na＋2H2O＝2NaOH＋H2↑ 2NaOH+CuSO4=Na2SO4+Cu(OH)2↓ Or 2Na+2H2O=2NaOH+H2↑　NH4Cl+NaOH=NaCl+NH3↑+H2O　⑺With oxides: 4Na+CO2=ignite=2Na2O+C↓