Meaning of relative atomic mass, meaning of formula level formula 100

wnhtmgmgwgatmw said: Hello! The spirit of learning is commendable! As far as I understand it, I'll talk to you briefly.

First of all, we know that matter is mostly made up of atoms. Atoms, in turn, are made up of nuclei and electrons outside the nucleus. Through the Rutherford bombardment gold leaf experiment we get:

The mass of an atom is mainly determined by the mass of protons and neutrons within the nucleus. The electron mass is 1 1836 of the mass of a proton (neutron), which is negligible. And the mass of protons and neutrons is also very small, and it is too inconvenient to write a lot of them.

Those chemists have found that the difference in the single mass of protons (neutrons) of different atoms is very small, and the difference between the mass of a proton and a neutron is also very small, and it is too troublesome to use the actual atomic mass when doing calculations, so smart people measure the mass of carbon-12 atoms (each carbon atom has 6 protons and 6 neutrons, so it is called C12) very accurately, with its 1 12 as the unit "1", (about equal to half of the mass of a proton + neutron, and also avoid the subtle difference between the mass of protons and neutrons). And because, most atoms have an equal number of protons and neutrons. Namely:

There is "relative atomic weight = number of protons + number of neutrons; One said).

The formula is there: the other atomic mass is divided by the carbon 12 atomic mass and then multiplied by 12.

This is my own understanding, you can understand it slowly.

The meaning is the ratio of (a) the (true) mass (m) of an atom (a) of the (true) mass (mc) of a standard carbon atom (mc) 1 12.

The formula is: m (mc 12) = m mc 12

The relative atomic mass is compared to the mass of carbon-12 which is 12, and the mass of the other atoms is divided by the mass of carbon-12 and then multiplied by 12.

Relative atomic mass refers to the ratio of the true mass of any atom to 1 12 of the mass of a carbon-12 atom as the standard, which is called the relative atomic mass of the atom.

In the study of chemistry, the first thing to come into contact with is the periodic table of chemical elements, each element on the periodic table has its own relative atomic mass, so you can clearly distinguish the differences between different elements, and the lowest number in the periodic table is the relative primordial mass of the element.

Since the actual mass of an atom is small, like the actual mass of a hydrogen atom:; The actual mass of an oxygen atom:.

The concept of atomic weight was first proposed by the British scientist John Dalton, who published the "atomic theory" in 1803, proposing that all matter is composed of atoms, and he believed that the atoms of the same kind of chaotic elements have the same mass, and the atomic masses of different elements are different, and the mass of hydrogen atoms is used as the benchmark for relative atomic mass.

Later, the mass of the oxygen atom and the mass of the carbon atom were used as the benchmark for the relative atomic mass, and the definition of atomic weight was finally proposed by the International Commission on Relative Atomic Mass. The mass of the carbon-12 atom selected internationally is 1 for hydrogen and 12 for carbon.

Relative atomic mass= the mass of a certain atom A carbon atom mass of (1 12) bark =The original row holds the neutron nucleusMass + extranuclear electron mass [(1 12]mc=mass of the proton + mass of the neutron (1 12)mc=Number of protons+ Number of neutrons. ”

Relative atomic mass is a way to calculate the mass of an atom, and since the actual mass of atoms is very small, it would be very troublesome if people used their actual masses to calculate it, such as a hydrogen atom.

The actual mass is kilograms, and the mass of an oxygen atom is kilograms. The mass of one carbon-12 atom is kilograms.

NEED NOTICE:

When we count a water molecule.

When the mass is, it will find extremely inconvenient to calculate. This is even more cumbersome when calculating the mass of other, more complex molecules. Therefore, it is internationally stipulated that the relative atomic mass and relative molecular mass should be used.

to represent atoms.

The mass relationship of the molecule. The relative molecular mass is numerically equal to the molar mass.

But the units are different. The unit of relative molecular mass is "1", while the unit of molar mass is g mol.

The mass of a carbon-12 atom is divided into 12 equal parts, (there are several carbon atoms, among which there is a carbon atom that contains 6 protons and 6 neutrons in its nucleus, which adds up to 12, so it is called carbon-12.)

Of course, there are others such as carbon-14, which contains 8 neutrons and 6 protons, which add up to 14. The reason why carbon-12 is chosen instead of carbon-14 is that when carbon-12 atoms are selected as the standard, the relative atomic masses of other atoms are close to integers, which is easy to remember and use).

Relative atomic mass

The mass of a certain atom The mass of a carbon atom (1 12) = nucleus.

Mass + extranuclear electron mass [(1 12]mc = mass of the proton + mass of the neutron (1 12) mc = number of protons.

+ Number of neutrons. "Relative atomic mass is a way of calculating the mass of an atom, and since the actual mass of an atom is very small, it would be very troublesome if one used their actual mass to calculate the source, such as a hydrogen atom.

The actual mass is kilograms, one oxygen atom.

The mass is kilograms. The mass of one carbon-12 atom is kilograms.

There are several: relative atomic mass m = mass m the amount of matter n m = = m n

The relative atomic mass of an atom = the actual mass of the atom 1 12 of the carbon-12 mass).

In one, is how many times the density of a certain gas, equal to x* the atomic mass of this gas.

Relative atomic mass = mass of a certain atom of carbon atomic mass (1 12). Next, the formula for calculating the relative atomic mass is shared for reference.

Relative atomic mass = mass of a certain atom of carbon atomic mass (1 12).

Nuclear mass + extranuclear electron mass [(1 12]mc

Nuclear mass (1 12)mc

The mass of the proton + the mass of the neutron (1 12)mc

Number of protons * mass of one proton + number of neutrons * mass of one neutron] (1 12) mc

Number of protons * (1 12) mc + number of neutrons * (1 12) mc] (1 12) mc

Number of protons, state car + number of neutrons.

Relative atomic mass refers to the ratio of the average atomic mass of any atom to the mass of a carbon-12 atom 1 12 using 1 12 of the atomic mass of a carbon-12 as the standard, which is called the relative atomic mass of the atomic epoch. The atomic weight is a unit of mass, the symbol u, which is defined as 12 12 of the atomic mass of carbon.

The international basic unit of relative atomic mass is 1. When we calculate what the mass of a water molecule is, we find it extremely inconvenient to calculate. This is even more cumbersome when calculating the mass of other, more complex molecules.

Therefore, it is internationally stipulated that the relative atomic mass and relative molecular mass are used to express the mass relationship between atoms and molecules. The relative molecular mass is numerically equal to the molar mass, but in different units. The unit of relative molecular mass is "1", while the unit of molar mass is g mol.