Answer:
The answer is the second option
Explanation:
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For a neutral atom, the number of positive protons is equal to the number of negative electrons and the charge is zero.
For this question, we see that the number of protons exceeds the number of electrons by 2, which means that this ion in a positively charged charged ion with charge of +2.
Pure substances can or can not be chemically combined.
Pure substances can be either elements or compounds, but not mixture. Mixture are different substances mixing together without being chemically combined, such as air, which is a mixture of oxygen, carbon dioxide, water etc. Mixture can be separated by physical methods, like filtration or decantation.
Meanwhile, elements are the substances that cannot be further separated by any means. No matter physical or chemical methods. Examples of elements are oxygen, hydrogen, neon and all the other ones from the periodic table. Compounds are basically elements joining together, but they’re chemically combined which means their electrons (kind of subatomic particle) are either shared or given away. These elements can only be separated by chemical methods like electrolysis or heating.
Therefore, as long as the substance cannot be separated by physical methods, it can be considered as a pure substance. We can now conclude that pure substance can be (element) or can not be (compound) chemically combined.
The largest energy release will take place when the electron jumps between the greatest number of levels. In this case from infinity down to 2
This is the emitted photon with the most energy ( in the Balmer series), the highest frequency and therefore the shortest wavelength.
Balmer's original formula was
Wavelength = 3645.6 . 10^–10 ( n^2 / (n^2 – 4) )
When n => infinity
Wavelength = 3.6456 . 10^–7 m ( or 364.5 nm)
K2SO4 + BaBr2 -> 2KBr + BaSO4
BaSO4 is solid = precipitate
