Why is there a flame color reaction, and what are the common flame color reactions?

When the peripheral electrons of metal ions or atoms are heated, they gain energy, so that the electrons are excited from the low-energy orbital to the high-energy orbital, and these electrons in the high-energy orbital are extremely unstable and instantly return to the low-energy orbital. During this "fallback", the electrons release energy, usually in the form of light energy, thus showing different flame colors.

The phenomenon that the flame of some metals and their volatile compounds takes on different colors when burned is called the flame color reaction.

In general, the atoms or ions in matter are in the lowest energy stable state. However, when an atom or ion is excited by external energy, the electrons outside its nucleus will transition from a stable ground state to an unstable excited state. At this time, the excited atom or ion in an unstable state has to jump back from the excited state of the higher energy level to the ground state of the lower energy level, and the excess energy is radiated in the form of visible light.

Due to the difference in atomic structure and outer electron configuration, the wavelength of the emitted light is also different, and the flame color is also different.

It can be seen that the basic principle of the flame color reaction is the energy level transition of the electrons, although in this process, the motion state of the electrons in the atoms or ions changes, but the combination mode of the atoms or ions does not change because of this, that is, the composition of the atoms or ions has not undergone any qualitative change, so the flame color reaction should be included in the category of physical changes. In short, the phenomenon of light and heat is not necessarily a chemical change.

Why do metals react with flames?

When burning metals or their volatile compounds, the electrons outside the nucleus absorb a certain amount of energy, and transition from the ground state (the stable state in which the electrons move around the nucleus, the energy of this state is the lowest, and the orbit of motion is closest to the nucleus) to the excited state with higher energy, the atom in the excited state is unstable, so it has to return to the ground state, and when the electrons return to the ground state, they will release excess energy in the form of spectral lines of a certain wavelength. The spectrum of each element has some characteristic spectral lines, which emit a characteristic color to color the flame, and the presence of a certain element can be judged according to the flame color.

Metals that do not react with flame color can also undergo these changes, but the wavelengths emitted are not in the range of visible light. It's just that some of the other elements don't have k,naIt's so obvious how easy to tell

The photon receives a transition in energy.

The common metals reacted with flame color are: sodium Na (yellow), lithium Li (purple red), potassium K (light purple), rubidium Rb (purple), calcium Ca (brick red), strontium SR (magenta), copper Cu (green), barium BA (yellow-green), cesium Cs (purple red).

The flame color reaction, also known as the flame color test or flame color test, is a reaction that causes a flame to take on its characteristic color when certain metals or their compounds are burned in a colorless flame.

The principle is that each element has its own special spectrum. Samples are usually in powder or small pieces. Load the sample with a clean and less active wire (e.g., platinum or nichrome) and place it in a matte flame (blue flame).

Chemically, it is often used to test for the presence of a metal in a compound.

Apply. (1) The flame color reaction can be used to detect some metal elements that cannot be identified by conventional chemical methods.

2) Different metals and their compounds react to different flame colors and are colorful in color, so they can be used to make fireworks for festivals.

The flame reaction of sodium should not be difficult to do, but it is the most troublesome to do. Because the flame color of sodium is yellow, while the flame of alcohol lamp is mostly yellow due to the unclean wick of the lamp head and the impurity of the alcohol. Even if the flame is almost colorless (light light blue), a new iron wire (or nickel wire, platinum wire) is burned on the outer flame, and the flame is yellow at the beginning, and it is difficult to tell whether the flame color is sodium ion or the flame color of the original alcohol lamp.

The yellow flame of sodium should be clearly visible.

The above content reference: Encyclopedia - Flame Color Reaction.

Common flame color reactions:

Contains sodium ions na yellow.

Contains lithium-ion li-purple-red.

Contains potassium ions K light violet (through blue cobalt glass).

Contains rubidium ions RB violet.

Contains calcium ions, CA brick red.

Contains strontium ions SR magenta.

Contains copper ions cu green.

Contains barium ion BA yellow-green.

Contains cesium ion CS purple red.

Fe containing iron ions is colorless.

The flame color reaction, also known as the flame color test and the flame color test, is a reaction that causes the flame to take on its characteristic color when certain metals or their compounds are burned in a colorless flame.

In chemistry, it is commonly used to test whether a metal is present in a compound. At the same time, using the flame color reaction, people consciously add specific metal elements to the fireworks to make the fireworks more colorful and colorful.

The flame color reaction is a reaction in which certain metals or their volatile compounds take on the characteristic color of a flame when it burns in a colorless flame. Some metals, or their compounds, can give a special color to the flame when burned.

This is because when the atoms of these metallic elements receive the energy provided by the flame, their outer electrons will be excited to the higher energy excited state.

The outer electrons in the excited state are unstable and have to transition to a lower energy ground state. The outer electrons of atoms of different elements have ground states and excited states of different energies.

In this process, electromagnetic waves of different wavelengths are generated, and if the wavelength of this electromagnetic wave is in the visible wavelength range, the characteristic color of this element is observed in the flame.

This property of the element can be used to test the presence of some metals or metal compounds. This is the flame color reaction in the material test.

In addition to the use of gas flames, Bunsen also uses coal flames, hydrogen flames, hydrogen flames, etc. After a detailed study of the flame color reaction, he also found that an element has no effect on the characteristic flame color of an element, even if it is in different compounds, even if there is a chemical change in the flame, even if the temperature of the flame is different, even if the type of flame used is different.

Later, at the suggestion of his friend physicist Kirchhoff, Bunsen realized the qualitative examination of elements by observing spectra, and created an important branch of analytical chemistry: spectroscopic analysis.

The flame color reaction is a physical change.

Extended Information: Flame reactions, also known as flame tests and flame tests, are reactions in which certain metals or their compounds take on a special color when they are burned in a colorless flame. The principle is that each element has its own individual spectrum.

Samples are usually in the form of powders or small pieces. The specimen is contained in a clean and less active wire and placed in a matte flame (blue flame).

The flame color reaction is a physical change. It does not generate new matter, the flame reaction is a change in the energy level of the electrons inside the atoms of matter, which is commonly said to be the change of the electronic energy in the atom, and does not involve the change of the structure and chemical properties of the matter.

Flame color reaction is a very ancient qualitative analysis method, as early as the Northern and Southern Dynasties in China, the famous alchemist and medicine master Tao Hongjing (456 -536) in his "Commentary on the Materia Medica" has such a record: "Burning it with fire, purple and green smoke rises, and the cloud is true saltpeter (potassium nitrate)".

In the modern chemical period in Europe after the 18th century, due to the great development of metallurgy and machinery industry, a larger quantity and more varieties of ores were required; At the same time, in order to reduce production costs, rationally use raw materials and improve product quality, new requirements are put forward for analytical chemistry.

In the middle of the 19th century, the famous German chemist Bunsen (1811-1899) designed and manufactured the Bunsen burner, which made the gas burn to produce an almost colorless flame with a temperature of more than 1,000 degrees.