Metal element sodium, which is soft in texture, can explain moisture and release hydrogen. The content of sodium 1 in the crust is 2.83%, ranking sixth. It mainly exists in the form of sodium salt, such as salt (sodium chloride), Chilean saltpeter (sodium nitrate) and soda ash (sodium carbonate). Sodium is also one of the main components of human muscle and nerve tissue. In ancient Chinese, the word "sodium" means wrought iron.

chemical property

The outermost layer of sodium atom has only 1 electron, which is easy to be lost. Therefore, the chemical properties of sodium are very active. When it reacts with other substances, its valence rises from 0 to+1. Strong sense of metal.

Reaction of sodium with oxygen

At room temperature, 4Na+O2 = 2Na2O (white solid)

After ignition, 2na+O2 = Na2O2 (light yellow powder)

When sodium is ignited in the air, it quickly melts into a shiny ball, giving off a yellow flame and generating sodium peroxide. Sodium peroxide is more stable than sodium oxide, which can combine with oxygen to form sodium peroxide. The chemical equation is: 2Na2O+O2=2Na2O2.

2. Sodium can directly react with nonmetals such as halogen, sulfur, phosphorus and hydrogen to generate corresponding compounds, such as

2Na+Cl2=2NaCl

2na+s = Na2S (sodium sulfide) (sodium and sulfide will explode when combined with grinding).

3. The reaction of sodium with water

Add some water to the beaker, drop a few drops of phenolphthalein solution, and then put a small piece of sodium into the water.

The observed phenomena and the conclusions drawn from them are as follows:

1. Sodium floats on the water (the density of sodium is less than that of water).

2. Sodium melts into a shiny ball (sodium reacts with water to release heat, and sodium has a low melting point).

3. Sodium swims around on the water (producing gas)

Reaction of sodium with water

4. Make a hissing sound (generate gas and react violently)

5. The water dripping with phenolphthalein test solution in advance turns red (produces alkali).

reaction equation

2Na+2H2O=2NaOH+H2↑

★ Sodium will burn hydrogen because of this violent reaction, so the sodium fire cannot be put out with water, and it must be put out with dry sand. Sodium has strong reducibility and can replace some metals in molten metal halides. Because sodium reacts easily with water, it is impossible to replace the metal after sodium in the metal active sequence with sodium in its salt solution.

4. Sodium reacts with acidic solution.

The reaction of sodium with acidic solution involves the amount of sodium. If sodium is small, it can only react with acids, such as sodium and hydrochloric acid:

2Na+2HCl=2NaCl+H2↑

If sodium is excessive, it will react with acid first, and then with water in acid solution. See equation 3.

5. Sodium reacts with salt.

(1) reacts with salt solution.

When sodium is put into a salt solution, it will first react with the water in the solution, and the generated sodium hydroxide will continue to react if it can react with salt.

If sodium is put into copper sulfate solution:

2Na+2H2O=2NaOH+H2↑

2NaOH+CuSO4=Na2SO4+Cu(OH)2↓

(2) reacting with molten salt

Most of these reactions are displacement reactions, which are common in metal smelting industry, such as

4Na+TiCl4 (melting) =4NaCl+Ti (high temperature)

Sodium +KCl = potassium+sodium chloride (at high temperature)

★ The reaction between sodium and molten salt cannot prove the strength of metal activity.

6, the reaction of sodium and organic matter

Sodium can also react with some organic substances, such as sodium and ethanol;

2Na+2C2H5OH→2CH3CH2ONa+H2↑

② Why is it not good to use aluminum for tableware?

Aluminum is not an essential element for human body. When human body is short of aluminum, it will not bring any harm to human body. On the contrary, aluminum salts can cause human poisoning. As early as 1965, Crazo first discovered that there were neurofibrillary tangles in the brain of rabbits with aluminum poisoning, but it did not attract people's attention. It was not until 1973 that he pointed out that the aluminum content in the cerebral cortex of cats increased, causing obvious brain dysfunction, which awakened the world.

Aluminum is toxic to living things, especially to human body. Soluble aluminum compounds are toxic to most plants. Aluminum compounds dissolved in water in acidic soil make it difficult for ordinary crops to grow normally. Usually, when the dissolved aluminum reaches more than 10-20PPM, plants will show signs of aluminum poisoning. Aluminum in soil can combine with soluble phosphate to produce insoluble aluminum phosphate, which leads to the death of plants due to phosphorus deficiency. Aluminum can also dehydrate plant cell protoplasm, and then destroy it and die. Aluminum combines with pectin in the cell wall, which strengthens the cross-linking structure of pectin and prevents plants from absorbing water and nutrients. Aluminum is also closely related to mineral nutrition such as calcium and phosphorus in plants. It can inhibit the absorption and accumulation of calcium and phosphorus by ordinary plants, and also affect their absorption and accumulation of potassium, magnesium, iron, manganese, copper, zinc and other elements. Aluminum is also toxic to aquatic animals. When the PH value is about 5, it is deposited in the gill of fish in the form of aluminum hydroxide, which makes it difficult for oxygen to enter the blood, which makes the salt concentration in fish out of balance and leads to fish death. The toxic concentration of aluminum to aquatic animals is generally above 70 μ g/L. The increase of aluminum content in water will lead to the coagulation of a large number of organic substances, which will lead to the death of aquatic animals due to lack of nutrition. Aluminum will precipitate phosphorus, which seriously threatens the reproduction of aquatic animals.

Once aluminum salt enters the human body, it is first deposited in the brain, which may lead to brain damage and severe memory loss, which is a unique symptom of Alzheimer's disease. The researchers involved in this work said that experiments on mice showed that the aluminum content in their brains reached a measurable level only after they were given a glass of water treated with aluminum salt. The study of mice found that the trace aluminum mixed in drinking water entered the brain of mice and gradually accumulated there. Researchers' research on dementia patients found that the aluminum concentration in 30% neocortex area of the brain of such patients was above 4 μ g/g (dry weight), and the aluminum content in neuron nuclei of patients' brains was four times that of healthy people, and the highest aluminum content could reach 30 times. Researchers believe that if aluminum gradually accumulates in the brain over time, it will kill neurons and make people lose their memory. A scientist said: We have been drinking water purified by aluminum salt and eating food containing aluminum salt all our lives, so when we are very old, we have accumulated a lot of aluminum in our bodies. He pointed out that in the past 70 years, the incidence of Alzheimer's disease has generally increased around the world. He said that aluminum is also used as food emulsifier.

Aluminum can directly damage the activity of osteoblasts, thus inhibiting the matrix synthesis of bone. At the same time, the absorption of aluminum by the digestive system leads to an increase in urinary calcium excretion and insufficient calcium content in human body. Aluminum accumulates in the human body and plays a physiological role, which can also lead to encephalopathy, osteopathy, nephropathy and non-iron deficiency anemia.

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