(air, oxygen)

1. determination of oxygen content in air: experimental phenomena: ① red phosphorus (charcoal, sulfur, iron wire, etc.) cannot be replaced. ) burning, producing a lot of white smoke; ② At the same time, the water level in the bell jar gradually rises, and after cooling, the water level rises by about 1/5 volume.

If the measured water level rise is less than 1/5 volume, the possible reasons are: ① insufficient red phosphorus and incomplete oxygen consumption; ② Air leakage of equipment; ③ Before cooling to room temperature, open the spring clip.

2. French chemist lavoisier proposed that air is mainly composed of oxygen and nitrogen.

3. According to the volume fraction, the composition of air is about nitrogen, oxygen, rare gas (mixture) and carbon dioxide, and other gases and impurities are 0.03%. The composition of air is mainly nitrogen and oxygen, which belong to a mixture.

The harmful substances discharged into the atmosphere can be roughly divided into dust and gas. Most gaseous pollutants are SO2, CO and NO2, which mainly come from the combustion of fossil fuels and the waste gas from factories.

5. Combustion: The violent oxidation reaction between combustible substances and oxygen in the air releases light and heat.

The combustion conditions are: (1) combustible, (2) contact with oxygen, and (3) the temperature reaches the ignition point.

Fire extinguishing methods: ① isolate the air; ② Reduce the temperature below the ignition point.

Similarities and differences among combustion, slow oxidation and spontaneous combustion

The same point is: all belong to oxidation reaction, and all give off heat.

The differences are as follows: combustion and spontaneous combustion react fiercely, releasing light and heat; Slow oxidation only releases heat and does not emit light.

6. Oxygen is colorless and odorless, slightly denser than air, insoluble in water, and liquid oxygen is light blue.

Oxygen is a kind of active gas, which has oxidizing and combustion-supporting properties, and is a commonly used oxidant. Purpose of oxygen: ① Support combustion ② Supply breathing.

Chemical properties of oxygen

(1) The phenomenon that (black) C reacts with O2 is that it is more intense in oxygen than in air and emits white light.

The chemical equation is:

② The phenomenon that (light yellow) S reacts with O2 is that the flame in the air and the flame in oxygen generate the malodorous gas SO2. The chemical equation is:

③ The phenomenon that (red or white) P reacts with O2 is to produce a large amount, and the chemical equation (used for starting gun) is:

④ The phenomenon that (silvery white) Mg reacts with O2 is that it emits a lot of heat and dazzling light at the same time, producing white solid magnesium oxide. (Used of flares, etc. ) The chemical equation is:

⑤ The phenomenon that (silvery white) Fe reacts with O2 is that it burns violently and sparks are everywhere, producing black solid Fe3O4. Note: put a small amount of water or a layer of sand in advance to prevent the high-temperature melt from splashing and cracking the bottom of the gas container.

The chemical equation is:

⑥ Hydrogen combustion: a light blue flame is emitted. Equation: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

⑦ Carbon monoxide combustion: blue flame. Equation: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

⑧ Methane combustion: it emits a bright blue flame. Equation: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Pet-name ruby alcohol combustion

(water)

1. Water is widely distributed on the earth. Rivers, lakes and oceans account for about 3/4 of the earth's surface area, and the human body accounts for about 2/3 of its mass. However, fresh water resources are not abundant, and the surface fresh water quantity is less than 1% of the total water quantity, and the distribution is very uneven.

2. Water pollution comes from ① waste residue, waste water and waste gas in factory production, ② arbitrary discharge of domestic sewage, and ③ pesticides and fertilizers used in agricultural production flow into rivers with rainwater.

3. Measures to prevent and eliminate water pollution: ① Strengthen water quality monitoring; ② Industrial "three wastes" should be treated before discharge; ③ Rational (not prohibited) use of chemical fertilizers and pesticides in agriculture.

4. The experiment of electrolyzing water can prove that water is composed of hydrogen and oxygen; In chemical changes, molecules can be split into atoms, but atoms cannot be split. Write the equation: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

5. In electrolytic water, a positive electrode is generated, and a negative electrode is generated. The volume ratio (molecular number ratio) is, and the mass ratio is. In experiments, dilute H2SO4 and NaOH are often added to enhance the conductivity of water. The chemical equation of electrolytic water is:

6. Hard water refers to relatively harmonious water. We can use soapy water to distinguish hard water from soft water. Soft water foam is more, hard water foam is less.

(carbon and carbon oxides)

1, and common elemental carbons are sum and C60. Diamond is hard; Graphite is soft and can be used as pencil lead, and graphite can be used as electrode. Graphite is greasy and can be used as high-temperature lubricant.

The reason why the physical properties of diamond and graphite are quite different is _ _ _ _ _ _ _ _ _ _ _ _

Activated carbon and charcoal have strong _ _ _ _ _ _ _ ability, so they can be used to remove odor and adsorb pigments.

Chemical properties: chemical properties of carbon at room temperature _ _ _ _ _ _ _

① Flammability: Charcoal burns in oxygen.

In the case of sufficient oxygen, the reaction equation is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

When oxygen is insufficient, the reaction equation is: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

② Reducibility: The reaction equation of reducing copper oxide with charcoal at high temperature is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

Phenomenon: Black powder turns red, producing gas to make limewater turbid.

Iron oxide is reduced by charcoal at high temperature, and the reaction equation is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

Under the condition of high temperature, carbon reduces carbon dioxide to produce carbon monoxide _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

2. Physical properties of carbon dioxide: it is soluble in water and its density is higher than that of air. "Dry ice" can be easily turned into solid by pressure cooling, which is used for fire fighting, greenhouse fertilizer, refrigeration and artificial rainfall, and is also a chemical raw material.

Chemical properties: (1) Under normal circumstances, CO2 does not support combustion and cannot be burned.

(2) Reacting with water: introducing carbon dioxide into water to generate carbonic acid CO2+H2O=H2CO3.

When carbon dioxide is introduced into the purple litmus test solution, the litmus test solution changes color, because (write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _; After heating, it turns into color again, because H2CO3 carbonate is unstable and easily decomposed to generate water and carbon dioxide. Write the chemical equation _ _ _ _ _ _ _ _ _ _ _ _ _ _.

(3) reacting with alkali to generate salt and water: (identifying CO2 with clarified limewater)

Introduce carbon dioxide into the clarified limewater (write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Phenomenon: white precipitate is produced (or: clear lime water becomes turbid).

Carbon dioxide reacts with sodium hydroxide (write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

3. Carbon monoxide is colorless, odorless, slightly less dense than air, and almost insoluble in water.

chemical property

① Flammability:

Carbon monoxide burns in the air to produce carbon dioxide (write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

② Reducibility: reduction of copper oxide by carbon monoxide (non-displacement reaction)

(Write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Phenomenon: Black powder turns red, producing gas that makes clear limewater turbid.

Reduction of iron oxide with carbon monoxide (write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

Pay special attention to the treatment of tail gas: carbon monoxide is highly toxic and will pollute the air. Unreacted carbon monoxide must be burned into pollution-free carbon dioxide.

③ Toxicity: Carbon monoxide inhaled into the lungs combines with hemoglobin in the blood, which destroys the oxygen permeability of hemoglobin.

The reason why the chemical properties of CO and CO2 are quite different is the different molecular composition.

(Ordinary metal)

Physical properties of iron: silvery white metallic luster, soft quality, good ductility and ductility, and it is a conductor of electricity and heat.

2. Tiesheng embroidery is actually the interaction of iron, oxygen and water, and the main component of rust is _ _ _ _ _ _ (reddish brown). The annual loss of steel due to raw embroidery accounts for about 1/4 of the world's annual output.

3. Methods to prevent iron products from embroidering: (1) Keep the surface of iron products clean and dry; (2) coating a protective film on the surface of the iron product. (such as: ① painting the surface, ② oiling the surface, ③ plating other metals on the surface of metal products, and ④ forming a dense oxide film on the surface of iron products through chemical reaction. (3) making alloy,

Rust removal methods: ① timely polishing ② dilute acid cleaning, such as Fe2O3+6HCl==2FeCl3+ 3H2O.

4. Alloy (mixture): It is a substance with metallic characteristics, which is formed by fusing one metal with one or more other metals (or nonmetals). The alloys of iron are: pig iron and steel (mixture)

The carbon content of pig iron is between and, and that of steel is between and.

Because of the different carbon content, the physical properties of pig iron and steel are very different.

The main equipment of ironmaking is blast furnace, and the main raw materials are iron ore, coke and limestone. Principle: Iron is reduced from iron oxide by reducing agent carbon monoxide at high temperature.

For example, reducing iron oxide with carbon monoxide (write the equation) _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Steelmaking equipment: converter, electric furnace, open hearth furnace. Principle: At high temperature, excess carbon and other impurities contained in pig iron are converted into gas and slag by oxygen or iron oxide and removed.

Several minerals: magnetite (), hematite (), siderite (), pyrite () and bauxite ()

6. Aluminum is a kind of metal with strong chemical activity, which can react with _ _ _ _ _ _ in the air at room temperature to form a dense oxide film, thus preventing aluminum from being further oxidized.

The chemical equation of this reaction is: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

(common acid)

1, acid is a compound in which all cations produced during ionization are H+. Such as hydrochloric acid (HCl), sulfuric acid (H2SO4) and nitric acid (HNO3).

2. Hydrochloric acid is an aqueous solution of hydrochloric acid. Pure concentrated hydrochloric acid is colorless. Hydrochloric acid is volatile, and concentrated hydrochloric acid will form white fog in the air. This is because the hydrogen chloride gas volatilized from concentrated hydrochloric acid contacts with water vapor in the air to form small drops of hydrochloric acid.

When concentrated hydrochloric acid is exposed to air, it will not deteriorate, but its mass and solute mass fraction will decrease.

3. Pure concentrated sulfuric acid is a colorless viscous oily liquid. Because of its water absorption, it is often used as a desiccant for some gases. When diluting concentrated sulfuric acid, it is necessary to slowly inject concentrated sulfuric acid into water along the wall of the device and stir it constantly with a glass rod to make the generated heat spread rapidly.

Concentrated sulfuric acid will not deteriorate when exposed to air, but the mass increases and the solute mass fraction decreases.

4. The nature of acid,

(1) Acidic solution turns purple litmus test solution red, but colorless phenolphthalein test solution does not change color;

(2) Replace the acid with a metal (before H, it reacts with the acid, but after H, it does not react)

Iron and hydrochloric acid: Fe+2HCl=FeCl2+H2↑ zinc and sulfuric acid: _ _ _ _ _ _ _ _ _ _ _ _

2Al+6 HCl = 2 ALCL 3+3 H2↑2Al+3 h2so 4 = Al2(SO4)3+3 H2↑

(3) Reaction between acid and metal oxide (write chemical equation)

Wash rust with hydrochloric acid: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Copper oxide and sulfuric acid _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(4) The reaction between acid and alkali (write the chemical equation)

Neutralize sodium hydroxide with hydrochloric acid: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Copper hydroxide and sulfuric acid: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

(5) the reaction between acid and salt

HCl+agno 3 = AgCl↓+HNO 3 h2so 4+bacl 2 = baso 4 ↓+ HCl

But note that BaSO4 and AgCl are insoluble in acid.

(common alkali)

Alkali is a compound, and all anions produced during ionization are OH-.

1, sodium hydroxide (common name: caustic soda, caustic soda, caustic soda chemical formula: NaOH)

Physical properties: white solid, easily soluble in water and giving off a lot of heat, with water absorption and easy to _ _ _ _ _.

Weighing must be carried out in glassware (such as beaker and watch mirror).

NaOH will absorb moisture in the air and react with carbon dioxide, so it must be sealed and preserved.

Usage: As a desiccant for neutral or alkaline gases, it cannot dry sulfur dioxide, carbon dioxide and hydrogen chloride.

It can dry H2, O2, N2, CO, NH3 CH4, etc. Used in soap, petroleum, paper and other industries.

Carbon dioxide and sulfur dioxide react with sodium hydroxide solution respectively (no obvious phenomenon)

When sodium hydroxide is exposed to air, it will deteriorate. Carbon dioxide +2 sodium hydroxide = sodium carbonate +H2O.

Sodium hydroxide solution absorbs sulfur dioxide SO2+2NaOH=Na2SO3+H2O.

Sodium hydroxide reacts with sulfur trioxide SO3+2NaOH=Na2SO4+H2O.

2. Calcium hydroxide (common name: hydrated lime, hydrated lime, and its aqueous solution is commonly known as lime water chemical formula Ca(OH)2)

White powdery solid, slightly soluble in water, the solubility decreases with the increase of temperature. It is made by the reaction of quicklime and water.

Uses: Hydrated lime can be used in the construction industry and used as industrial raw material to prepare sodium hydroxide. It can reduce soil acidity in agriculture and prepare pesticide Bordeaux mixture (hydrated lime and copper sulfate).

The difference between sodium hydroxide and calcium hydroxide is that calcium hydroxide reacts with carbon dioxide, sodium carbonate and potassium carbonate to produce white precipitate, while sodium hydroxide does not precipitate.

Carbon dioxide+calcium hydroxide = calcium carbonate ↓+H2O

Na2CO3+ Ca(OH)2 =CaCO3↓+2NaOH

Using water, limestone and soda ash as raw materials, a small amount of sodium hydroxide can be prepared through three steps under certain conditions. The chemical equations of these three reactions are (written in preparation order) (1) CaCO3 Cao+CO2 ↑; (2)CaO+H2O = Ca(OH)2； (3) Sodium carbonate+calcium hydroxide = = calcium carbonate ↓+sodium hydroxide. These three reactions belong to decomposition reaction, combination reaction and double decomposition reaction in turn.

There are some white material on the inner wall of reagent bottle, which can hold limewater for a long time. This is because CO2 in the air reacts with limewater to produce calcium carbonate CaCO3. The cleaning method is to use dilute hydrochloric acid. Please write the equation: _ _ _ _ _ _.

Properties of alkali:

Because alkali can ionize in aqueous solution to produce OH- ions, they have some similar chemical properties.

(1) alkaline solution can react with acid-base indicator. (Condition: Alkali must be soluble) Purple litmus test solution turns blue when it meets alkali, and colorless phenolphthalein test solution turns red when it meets alkali. For example, when purple litmus test solution is dropped into Fe(OH)3, litmus does not change color. Because iron hydroxide is insoluble in water, there is no OH-

(2) Alkali can react with most nonmetallic oxides to produce salt and water. Condition: The alkali must be soluble. For example, Cu(OH)2+CO2 does not react because copper hydroxide is insoluble in water, while sodium hydroxide and calcium hydroxide can react with CO2 and SO2.

Hydrated lime hardens in air: Ca (OH) 2+CO2 = CaCO3 ↓+H2O;

Caustic soda deteriorates in air: 2NaOH+CO2=Na2CO3↓+H2O.

Any oxide that can react with alkali to form salt and water is called acid oxide.

(3) Alkali can react with acid to produce salt and water. The reaction between acid and alkali to form salt and water is called neutralization reaction. If the medicine containing aluminum hydroxide is used to treat hyperacidity, the reaction is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

(4) Alkali can react with some salts to generate another salt and another alkali, provided that the reactants are soluble and the products are precipitated.

(salt)

1, salt is a compound formed when metal ions and acid ions are ionized.

2. The salt is sodium chloride, and the chemical formula is NaCl. Raw salt contains impurities such as MgCl2 and CaCl2, which will absorb moisture in the air and deliquesce. Normal saline is 0.9% sodium chloride solution. Industrial salt is sodium nitrite, which is toxic. Salt solution reacts with silver nitrate: NaCl+AgNO3 = Nano3+AgCl ↓

3. The chemical formula of sodium carbonate is Na2CO3, commonly known as soda ash and soda ash. Hou is a famous chemist in China and has made outstanding contributions to improving soda production.

Note: Sodium carbonate Na2CO3 is a salt, but its aqueous solution is alkaline, so the acid-base indicator cannot be used to distinguish sodium carbonate from alkali. But dilute hydrochloric acid can be used, which will produce bubbles. For example: sodium carbonate+hydrochloric acid = sodium chloride +H2O+ carbon dioxide =

You can also use lime water to turn it into turbid (white precipitate) Na2CO3+Ca(OH)2==CaCO3↓+2NaOH.

4. Chemical formula of sodium bicarbonate: NaHCO3, commonly known as baking soda. Compared with sodium carbonate, its chemical properties are unstable, and it is easy to decompose 2 nahco3 Na2CO3+H2O+CO2 when heated.

It can also react with acids, such as nahco3+HCl = = NaCl+H2O+CO2 = When the skin is inadvertently stained with sulfuric acid, it should be immediately coated with 3%-5% sodium bicarbonate solution and rinsed with water.

5. Calcium carbonate CaCO3 is the main component of limestone and marble.

Can react with hydrochloric acid to generate carbon dioxide, and its chemical equation is: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

Limestone is calcined at high temperature in industry to produce calcium oxide, namely calcium oxide. The reaction is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.

6. Chemical properties of salt (soluble salt)

(1) reacts with some metals to form another metal and another salt, provided that ① the salt is soluble ② the metal ranked first in the activity sequence table can replace the last metal from its salt solution. (K, Ca and Na are too active to be replaced by salt), such as Fe+CuSO4=FeSO4+Fe.

(2) Salt reacts with acid, 2 HCl+Na2CO3 = 2 NaCl+H2O+CO2 =

(3) salt reacts with alkali

FeCl 3+NaOH = NaCl+Fe(OH)3↓cuso 4+2 NaOH = na2so 4+Cu(OH)2↓

(4) salt reacts with salt.

NaCl ++ agno 3 = AgCl↓+nano 3 cuso 4+bacl 2 = baso 4 ↓+ cuc L2

Soluble acids, bases and salts can ionize anions and cations that move freely in water, so their aqueous solutions can conduct electricity.

(common chemical fertilizer)

1, nitrogen fertilizer: nitrogenous fertilizer, such as urea CO(NH2)2 and ammonia NH3? H2O, ammonium bicarbonate, ammonium chloride, ammonium nitrate, sodium nitrate and so on. Among them, urea has the largest nitrogen content.

The role of nitrogen fertilizer: promote the growth of crop stems and leaves, flourish and leave dark green.

Ammonium-containing fertilizers, such as ammonium bicarbonate, ammonium chloride, ammonium nitrate, etc. Generally, it is easy to decompose when heated, and at the same time, it is easy to react with alkali to release ammonia with pungent smell. When using it, it should be avoided to mix with alkaline substances.

2. Phosphate fertilizer: Phosphorus-containing fertilizer, such as phosphate rock powder Ca3(PO4)2 calcium magnesium phosphate, calcium superphosphate, etc.

Function: Promote root system development and enhance drought and cold resistance.

3. Potash fertilizer: fertilizer containing potassium, such as potassium nitrate KNO3, potassium dihydrogen phosphate KH2PO4, potassium sulfate K2SO4, potassium chloride KCl, etc.

Function: promote plant growth, strengthen resistance to pests and diseases, lodging and so on.

4. Compound fertilizer refers to chemical fertilizer containing two or more nutrient elements, such as KNO3.

Step 5 identify

Nitrogen, potassium and phosphate fertilizer

Look at the appearance, white crystal, gray powder.

Adding water to dissolve in water is mostly insoluble or slightly soluble in water.

Combustion can burn, melt, bubble or smoke without burning, jumping or bursting.

Adding slaked lime releases ammonia with pungent smell, but there is no pungent smell.

(Molecules, atoms, ions, elements, valence)

1. Molecules are the smallest particles that keep the chemical properties of substances (atoms and ions can also keep the chemical properties of substances). .

For example, the smallest particle that keeps the chemical properties of chlorine gas is chlorine molecule (Cl2). The smallest particle that keeps the chemical properties of CO2 is CO2 molecule; The smallest particles that keep the chemical properties of mercury are mercury atoms. What kind of particles a substance is made of will keep its chemical properties. The smallest particles in this change of electrolytic water are hydrogen atoms and oxygen atoms.

Atoms are the smallest particles in chemical changes. Atoms are composed of nuclei and extranuclear electrons, while nuclei are composed of protons and neutrons. The three kinds of particles that make up atoms are protons (positively charged), neutrons (uncharged) and electrons (negatively charged). Do all atoms have protons, neutrons and electrons? (wrong! Generally, hydrogen atoms have no neutrons).

The relative atomic mass of an atom =112/c atom with an atomic mass. The unit of relative atomic mass is "1", which is a ratio. The unit of relative molecular mass is "1".

In atoms: relative atomic weight = number of protons+number of neutrons.

Number of nuclear charges (positively charged) = number of protons = number of extranuclear electrons (atoms are uncharacteristic)

3. Ions, charged atoms or atomic groups. The positively charged ions are called cations (that is, there are more protons in the nucleus than electrons outside the nucleus), such as Na+Mg2+NH4+; The negatively charged particles are called anions (the number of protons in the nucleus is less than the number of electrons outside the nucleus), such as Cl-O2-SO42-. In the solution, anions and cations exist at the same time, and the positive and negative charges are equal, so the solution does not show electricity.

4. Element: the general name of a kind of atoms with the same nuclear charge number (proton number), which determines the type of element (that is, the essential difference between one element and another is the difference in proton number or nuclear charge number); It is the number of electrons in the outermost layer that determines the chemical properties of elements. The same element has the same nuclear charge, such as Fe, Fe2+ and Fe3+, which are called iron elements because of the same nuclear charge, but the outermost electrons are different, so their chemical properties are different.

The most abundant elements in the earth's crust are oxygen, silicon, aluminum and iron. The compound with the most metallic and nonmetallic elements is Al2O3.

Dictation of symbols and names of 1-20 elements;

Symbol:

Name:

5. Valence

Valence of common elements:

Named ammonium hydroxide nitrate sulfate carbonate phosphate

Symbol NH 4 Ohno 3 so 4 co 3 po 4

Price+1-1-1-2-3

Ion NH4+OH-NO3-SO42-CO32-PO43-

+1 valence k, Na, Ag, h; +2 valence calcium, magnesium, barium, zinc and mercury;

+trivalent aluminum; +4 valence silicon; +5 valent phosphorus

O is generally -2 valence, Cl is generally-1 valence, iron has +2 valence and +3 valence, and iron with +2 valence is generally called bivalent iron.

Symbols and valence of common atomic groups

6. Matter consists of molecules, atoms and ions.

Directly composed of atoms: simple metals, rare gases and most solid nonmetals.

Directly composed of molecules: nonmetallic gases, such as H2, oxygen, N2, chlorine, etc. And valence compounds such as CO2, H2O, etc. Molecules are made up of atoms. In chemical changes, molecules can be subdivided.

Directly composed of ions: ionic compounds (metals and nonmetals or atomic groups), such as NaCl, CaCl2, MgS, NaF, ZnSO4. The particles that make up potassium chlorate are K+ and ClO3-.

7, atomic structure diagram, the total number of electrons outside the nucleus is equal to the number of protons in the nucleus, such as

The chlorine atom of 17 element has three electron shells, and the outermost seven electrons can easily get one electron.

Schematic diagram of ion structure, the total number of electrons outside the nucleus is not equal to the number of protons inside the nucleus, such as

Chlorine atom and chloride ion are the same element, because the number of protons in the nucleus is equal, but the outermost electrons are not equal, so the chemical properties are different.

(Element symbol, chemical formula)

1, meaning of element symbol: macro: an element, micro: an atom of this element.

For example, H: hydrogen, hydrogen atom.

But if you add the coefficient, it only represents the micro, not the macro. For example, 2H means two hydrogen atoms, because elements only talk about types, not quantities.

2. Meaning of chemical formula: Macroscopically, it refers to a substance and its elemental composition.

Microscopy: the molecule representing this substance and the atomic composition of the molecule representing this substance. Plus the coefficient only shows the micro, not the macro.

For example: CO2: ① Carbon dioxide gas ② Carbon dioxide is composed of carbon and oxygen.

③ A carbon dioxide molecule ④ A carbon dioxide molecule consists of one carbon atom and two oxygen atoms.

And 2CO2 represents two carbon dioxide molecules.

3. The meaning of numbers in chemical symbols

① Before: indicates the number of particles, such as two potassium atoms 2K and three water molecules 3H2O.

② Right above: indicates the valence of elements, such as Fe(+2)2O3 iron oxide, with a valence of +2.

③ Lower right corner: The number of atoms contained in a molecule, such as CO2. A carbon dioxide molecule contains two oxygen atoms.

④ Upper right corner: the number of charges carried by ions is Mg2++, and a magnesium ion carries two unit positive charges.