Help solve the chemistry knowledge points in junior high school

1 The outermost electrons of the noble gas elements are (8 or 2), and helium is (2), and their chemical properties are stable, so the structure of the outermost shell with (8) electrons (only one electron shell is (2) electrons) is (stable structure).

2. The number of electrons in the outermost shell of a metal element is generally (less than 4), and it is easy to lose the point in the chemical reaction

3. The number of electrons in the outermost shell of non-metallic elements is generally (greater than or equal to 4), and it is easy to obtain electrons in chemical reactions

4 The properties of the element are closely related to (the number of electrons in the outermost shell).

5 (the number of electrons outside the nucleus is not equal to the number of protons in the nucleus) is an ion, (the number of protons in the nucleus is greater than the number of electrons outside the nucleus) is a cation, and (the number of protons in the nucleus is less than the number of electrons outside the nucleus) is an anion.

6 Define the formula that uses elemental symbols to represent the composition of matter.

7 Implications. 8 Macroscopic 1 (for an element) 2 (for a substance).

9 Microscopic 1 (indicates that a substance is composed of an element) 2 (indicates that a certain molecule is composed of several certain atoms. ）

10 When writing the chemical formula of a compound, pay attention to 1 (positive valence in front and negative valence in front), 2 (metal element in front), 3 (the charge number of ions in the upper right corner), 11 chemical formula writing of elemental 1, noble gas (he) 2, metal (Fe) 3, non-metal (Na).

12. The valency of the elements in the compound should pay attention to the following points: 1. The valency has positive valence, negative valence and 1 2 3 4

Small 2 (valency changes in different substances) Small 3 (the sum of positive and negative valence equals 0).

13 Definition and Symbols of Relative Molecular Mass The sum of the relative atomic masses of each atom in a chemical formula is the relative molecular mass The symbol is: mr

1.8, 2, the outermost shell of 8 electrons, only one electron shell of 2 electrons is a stable structure.

2.The outermost electrons of metal elements are generally less than 4, and they are prone to lose electrons in the reaction.

3 The outermost electrons of non-metallic elements are generally greater than or equal to 4, and electrons are easily obtained.

4 Atomic structure.

5 Charged atoms or clusters of atoms; Positively charged atoms or clusters of atoms; Negatively charged atoms or clusters of atoms.

10 (1) When the ratio of the number of atoms of a constituent element is 1, 1 can be born (e.g. NaCl).

2) In the writing of oxides, the element symbol of oxygen is generally written on the right and the other is written on the left (such as CO).

3) When writing compounds composed of metal and non-metal elements, the metal elements are generally written on the left and the non-metal on the right (such as NaCl).

11 Noble gases are monoatomic molecules, and chemistry is the symbol of the elements; Metal elements directly write element symbols; Other non-metallic elements are written element symbols for monoatomic molecules, and polyatomic molecules are indicated by subscripts after the element symbol to indicate the number of atoms in a molecule.

12 (1) There are positive and negative valences: oxygen is usually -2 valence; Hydrogen is typically +1 valence; When metallic elements and non-metallic elements are combined, metals have positive valences and non-metallic negative valences; The same element may show different valence states in different compounds (formula: monovalent potassium, sodium silver, hydrogen chloride, divalent oxygen, calcium, barium, zinc, magnesium, trialuminum, tetrasilicon, pentavalent phosphorus, copper, mercury, bivalent are the most common) (2) The algebraic sum of the valency of the compound is zero (3) The valency of the element is a property exhibited by the element atom when forming a compound, and in the elemental molecule, the valency is zero.

13 Personal Answer: The sum of the relative atomic masses of the atoms in the molecular formula of matter, the symbol mr

1 The outermost electrons of the noble gas elements are (8), helium is (2), and their chemical properties are (extremely inactive), so the structure of the outermost shell with (8) electrons (only one electron shell is (2) electrons) is (stable structure).

2 The outermost electron number of metallic elements is generally (less than 4), and it is easy to lose electrons in chemical reactions3 The outermost electron number of non-metallic elements is generally (greater than or equal to 4), and it is easy (to gain electrons) in chemical reactions4 The properties of the element are closely related to (the number of outermost electrons).

5 (a particle that is charged and has only one nucleus) is an ion, (positively charged) is a cation, and (negatively charged) is an anion.

1.8, 2, 8, 8, relatively stable structure.

2.Less than 4, lose electrons.

3.More than 4 to get electrons.

4.The outermost electron number of an element's atom.

5.Charged atoms (or clusters of atoms), positively charged, negatively charged.

6.The formula that is composed of matter is expressed by a combination of element symbols and numbers.

7.The meaning of the chemical formula.

8.(1) Indicates a substance. (2) Indicates the constituent elements of the substance.

9.If the substance consists of molecules: (1) denotes one molecule of the substance. (2) Indicates the composition of the molecule of the substance.

10.(1) When the ratio of the number of atoms of a constituent element is 1, 1 can be omitted. (2) Oxide, generally the element symbol of oxygen is written on the right, and the symbol of another element is written on the left.

3) For compounds composed of metallic elements and non-metallic elements, the metal element symbol is generally written on the left and the non-metallic element symbol is written on the right.

11.(1) Represented by element symbols (2) Customarily represented by element symbols (3) Solid non-metallic: Customarily represented by element symbols. Non-metallic gases: Write a number in the lower right corner of the element symbol indicating the number of atoms contained in the molecule.

12.Small 2: Hydrogen usually shows +1 valence, and small 3: When metal elements are combined with non-metallic elements, metal elements show positive valence, and non-metallic elements show negative valence.

13.The sum of the relative atomic masses of the atoms in the chemical formula (symbol mr).

2,8,8,2, stable structure.

4. Loss of electrons.

4. Get electrons.

Structure. Charged atoms or clusters of atoms, positively charged, negatively charged.

There are elemental symbols that indicate the composition of matter.

Consists of several elements, one substance.

A molecule (atom) of the substance, the atomic composition of the substance.

Metals come first, non-metal oxides and non-metals come first, and the sum of valencies is zero.

The valency of atoms shows different valencies in different substances, and the valency of the elemental plasma is zero.

The sum of the relative atomic mass exponents, mr

1.8,2, stable, 8,2, helium.

2.Less than 4, lost electrons.

3.If it is greater than or equal to 4, electrons are obtained.

4.Structure.

5.Charged particles, positively charged, negatively charged.

6.The element symbol represents the formula that is made up of matter.

8,2,8,2, helium.

less than four, loses the outermost electrons.

Greater than four, electrons are obtained.

The number of outermost electrons.

Atoms that are electrically charged, positively charged, and negatively charged.

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