The chemical terminology is a growing proportion of the senior high school entrance examination. Usually, the writing of chemical formulas, the calculation and labeling of valences, the writing of chemical equations, etc., are simple but easy to lose points. Why?~~~This is a ~~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
In Shaanxi, it is a yearly test Drops, in the multiple-choice questions, fill in the blank questions, there are test drops
Our Anhui, the examination of element symbols, chemical formulas, and ion symbols is more important, it is a must-test point
In our Yunnan, this is the key subject of the senior high school entrance examination. We generally check the 22 and 23 questions. The title is fixed, and the score is still big.
Our Hebei is also a year-end test, we only examine it in the multiple-choice question, which is very important for us too~~
Speaking of it, you still have to practice
! Come! Come! Let’s practice our hands and test the knife first~~
Experts secretly hurry to watch
I. Element symbol
1 Macroscopic meaning: an element; microscopic meaning: an atom representing this element.
2 Among the common first 20 elements, substances other than H, O, N, and Cl, which are directly composed of atoms, also represent such substances.
3 Add a number before the element symbol: only how many atoms are represented.
Second, chemical writing
(1) Elemental gases, metals and most non-metallic solids (except iodine-I2) are represented by elemental symbols. Such as:
Sodium (Na) Carbon (C) Helium (He)
(2) Elemental gas (except rare gases), some non-metallic solids and some non- The chemical formula of a metal liquid is expressed by first writing an element symbol, and then numerically indicating the number of the atoms in one molecule in the lower right corner of the element symbol. Such as:
hydrogen (H2) oxygen (O2) nitrogen (N2)
iodine (I2) bromine (Br2) ozone (O3)
(1) Common oxides (all containing oxygen, oxygen later)
a.Reading and chemical formula Inconsistent, such as:
iron oxide (iron oxide) (Fe2O3)
alumina (alumina) (Al2O3)
Hydrogen peroxide, hydrogen peroxide (H2O2)
b. The reading is consistent with the chemical formula—“after reading and writing”, eg:
oxidation Magnesium (MgO) Ferric oxide (Fe3O4)
Carbon dioxide (CO2) Phosphorus pentoxide (P2O5)
(2) Acid (both H+, H+ on the left, acidate) On the right, H+ shows +1 price), such as:
hydrochloric acid (HCl) sulfuric acid (H2SO4) nitric acid (HNO3)
(3) alkali (both OH-, OH- On the right, the metal ion or ammonium ion is on the left, OH-displays -1 valence), such as:
sodium hydroxide (NaOH) calcium hydroxide [Ca(OH)2]
a. Chloride (all containing Cl-, Cl- is on the right, metal ion or ammonium ion on the left, Cl-display -1 valence), eg:
Zinc chloride ( ZnCl2) sodium chloride (NaCl)
potassium chloride (KCl) calcium chloride (CaCl2)
silver chloride (AgCl) copper chloride (CuCl2)
Barium chloride (BaCl2) Aluminum chloride (AlCl3)
ferric chloride (FeCl3) Ferrous chloride (FeCl2)
b.carbonate CO32-, CO32- on the right, metal ion or ammonium ion on the left, CO32-display-2 valence), eg:
sodium carbonate (Na2CO3) calcium carbonate (CaCO3)
potassium carbonate (K2CO3)
c.sulphate (both SO42-, SO42- on the right, metal ion or ammonium ion on the left, SO42-display-2), eg:
Sodium sulfate (Na2SO4) Copper sulfate (CuSO4)
Barium sulfate (BaSO4) Potassium sulfate (K2SO4)
Ferrous sulfate (FeSO4) Ferric sulfate [Fe2 (SO4) 3]
d.Nitrate (both contain NO3-, NO3- is on the right, metal ion or ammonium ion is on the left, NO3-display-1 price), eg:
Sodium nitrate (AgNO3) Sodium nitrate (NaNO3)
Nitrate potassium (KNO3)
1 The law is before the normal price, after the negative price; the valence price is marked on the head; the first reduction is followed by the cross; the algebraic sum is equal to zero.
a. The algebraic sum of the positive and negative valences of each element in the compound is zero
b. Right left negative right, price cross, simplification review, such as:
2If the chemical formula contains atomic groups, when the corner code of the atomic group is not 1, enclose the atomic group in parentheses, and then Write the corner code in the lower right corner of the right parenthesis.
Three, the difference between ionic symbols and valences
(1) The valence of the element is written directly above the element symbol, the symbol is written first, then the number is written, and the value 1 cannot be omitted.
(2) The ion symbol is written at the upper right of the element symbol, first writing the number, then writing the symbol, and the value 1 can be omitted.
The valence of the element is equal to the charge value of the ion, and the sign is the same. For example, in sodium chloride, sodium shows a +1 valence, that is, a sodium ion carries a unit of positive charge.
Four, the meaning of chemical formula (in the case of NaCl)
(1) indicates a substance (sodium chloride)
(2) indicates the elemental composition of this substance (the composition of chlorine and sodium)
(3) indicates the elemental mass ratio of each element in the substance (Na:Cl=23:17)
(1 ) indicates a molecule of this substance (a sodium chloride molecule)
(2) indicates the composition of the molecule (each sodium chloride molecule consists of one chlorine atom and one sodium atom)
(3) indicates the ratio of the number of atoms in one molecule (Na:Cl=1:1)
Five, the meaning of the numbers around the chemical formula>
Six, the writing and meaning of the chemical equation
1. Writing principle :
(1) must be guest Fact-based;
(2) must comply with the law of conservation of mass.
2. Writing steps
(1) Write the chemical formula of the reactants and products on both sides of the short line. Indicate the reaction conditions and the state of the product;
(2) Level and change the short line to the equal sign.
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