What does the plus or minus sign in the upper right corner of the chemical formula of the atomic clu

That's the price of electricity. For example, hydroxide oh - denotes negative monovalent; Carbonate 2-subscript 3 indicates negative trivalent.

If you want to form a new substance with other substances, the new substance must have equal positive and negative valences, for example, water is H2O, containing an OH - and an H+, both positive and negative are monovalent, and a stable substance can be generated.

The positive and negative signs are positively or negatively charged, and the superscript number after them is with several charges, such as CO32-, oxygen is negatively charged, -2 valence, 3*2 is negative, carbon +4 valence, 4-6=-2, so carbonate is -2 valence.

The superscript is the number of charges carried by the group, and the subscript is the number of atoms. This is on the right ... In the middle is the elemental valency.

The number on the top left is the mass number, such as c14 (14 on the top left), and the number of protons on the bottom left.

It's basically complete.

is -1 valence, -2 is negative 2 valence, which indicates the charged number of this atomic cluster, and each atomic cluster or ion has its own charged number, its own valence state

The valence electrons carried by the atomic cluster, such as hydroxide, "- represent the atomic cluster showing -1 valence.

Hydroxide oh hydroxide ions have a negative charge of 1 unit.

Carbonate Carbonate ions have a negative charge of 2 units.

Nitrate no nitrate ion carries a negative charge of 1 unit.

Sulfate so sulfate ions have a negative charge of 2 units.

The charged atomic cluster is an ion, and it must be added with a plus or minus sign, but not in the chemical formula.

There are some substances in which there are groups of atoms that are made up of several atoms, and in a chemical reaction they participate in the reaction as a whole, as if they were one atom, and such groups of atoms are called clusters. When an atomic cluster is charged, it is also called an ion.

Common atomic clusters include sulfate in copper sulfate, carbonate in carbonic acid, hydroxide in sodium hydroxide, sulfite in sulfurite, nitrate in silver nitrate, ammonium in ammonium chloride, etc.

Clusters of atoms, like atoms, also show a certain valency in the compound, which is called the root valence. For example, the sulfate in copper sulfate is -2 valent. In a compound, the algebraic sum of the valency of the atoms and clusters of each element is zero, which is the valency rule.

Sometimes, the molecule of a compound is made up of only one group of atoms, such as cyanide, with the chemical formula (CN)2, in which case the root valence of this cluster is zero.

Based on the valency of the element and the root valence of the atomic cluster, the chemical formula of some compounds can be written, such as the chemical formula of magnesium hydroxide is mg(oh)2. If you want to represent more than two atomic clusters, you should put parentheses around the clusters and then mark the numbers in the lower right corner of the brackets.

Acid is a compound composed of hydrogen elements and acid groups, which can completely ionize hydrogen ions in aqueous solution, which is a strong acid, such as hydrochloric acid, sulfuric acid, nitric acid, etc., and vice versa, a weak acid, such as carbonic acid, acetic acid, hydrosulfuric acid, etc. Concentrated sulfuric acid and nitric acid are not only strong acids, but also strong oxidants, which can oxidize certain substances and make these substances oxygenated.

Alkali is a compound composed of metal elements or ammonium and hydroxide, which can completely ionize hydroxide ions in aqueous solution, which is a strong base, such as sodium hydroxide, calcium hydroxide, potassium hydroxide, etc., and is insoluble in water or cannot completely ionize hydroxide ions in aqueous solution, which is a weak base, such as copper hydroxide, ammonium hydroxide, etc.

There is also a class of compounds that belong to salts, salts are compounds composed of metal elements or ammonium and acid groups, they are generally strong electrolytes, and some salts are strong oxidants, such as sodium chloride, silver nitrate, copper sulfate, calcium carbonate, potassium chlorate, potassium permanganate, etc.

I hope I can help you with your doubts.

Carbonate. Ion: co

Sulfate. Ion: SO

Nitrate ion: no

In the chemical formula of a substance, it should be written according to the writing specification of the chemical formula, without an plus sign. For example, sulfuric acid: Hso

The positive and negative signs of the charge carried by the ion cluster cannot be omitted, and after the ion cluster and the oppositely charged particles are combined, they cancel each other out, so there is no need to write about it.

There are many kinds of compounds, you are asking about the charge of the ion, that must be written, it cannot be omitted anywhere, for example: no3 - charge cannot be omitted, no3 does not exist.

The numbers in the common atomic cluster symbols are determined according to the number of atoms involved in the reaction, or the outermost electrons of the atom, which must become the most stable structure after the reaction, such as NaCl

The number of electrons in the outer shell of sodium is 1, and the number of electrons in the outer shell of Cl is 9, so one sodium atom loses electrons, and chlorine gets one electron and it is stable, so the numbers are all 1, no need to write.

But CO2, the number of electrons in the outer shell of carbon is 4, and the number of electrons in the outer shell of O is 6, so one carbon atom loses 4 electrons and each oxygen atom gets 2 electrons, and it takes two to stabilize, so the numbers are both 2

【Answer】B【Answer Analysis】Test Question Analysis:

aBoth symbols denote the atom of the element iodine with proton number 53. This is correct. b The two atoms have the same number of protons, but the value in the upper left corner is different.

So they have different neutron numbers. This is incorrect. c In an atom, the number of electrons outside the nucleus = the number of protons, so the number of electrons outside the nucleus is the same for both atoms.

This is correct. The type of element d is determined by the number of protons (nuclear charge number) of its atoms. The two atoms have the same number of protons and belong to the same element.

This is correct. Therefore, item B should be chosen.

Test Place: Composition of Atoms.