Would Flame test be useful for detecting metal ions present in a mixture of metal ions??

It is not a reliable method. Atomic spectroscopy would be much more accurate and sensitive than the human eye.

To add to the information provided by Bob Pursely, which of course is correct, there are a limited number of ions that can be detected by blame tests. There are fewer than can be detected when in the presence of other ions. For example, Na can be detected easily. So can K. However, Na and K together, gives a problem because Na masks the color of K. That can sometimes be avoided by using a cobalt glass to filter the yellow part of the Na flame out. Ba, Sr, and Ca are ok by themselves but in mixtures they give problems. Copper, by itself, is usually seen easily but is often overlooked in mixtures. That is what Mr. Pursley means when he says the tests aren't reliable in mixtures.

Does atoms of the same element have the same number of protons?

Yes. An elements number of neutrons and electrons can change, but its number of protons will not vary. Therefore, the atoms of the same element do have the same number of protons.

Yes, atoms of the same element always have the same number of protons. The number of protons in an atom determines its atomic number, which is unique to each element. For example, all atoms of carbon have 6 protons, all atoms of oxygen have 8 protons, and so on. This is a fundamental characteristic of each element and is one of the key factors that define its properties.

Yes, atoms of the same element have the same number of protons. The number of protons in an atom determines its atomic number and defines the identity of the element. For example, all atoms of carbon have 6 protons, while all atoms of oxygen have 8 protons, and so on.