Answer:
In an atom, the first energy level can hold 2 electrons. The second energy level can hold 8 electrons. The third energy level can hold 18 electrons.
Explanation:
There are 7 energy levels, numbered from 1 to 7, and in which electrons are distributed. Each level is divided into sub-levels. These sub-levels into which each level is divided can be up to 4 and these are called: s, p, d, f. In the sub-level s there can only be a maximum of 2 electrons, in p there can be a maximum of 6 electrons, in the sub-level d 10 electrons and finally in the sub-level f there can be a maximum of 14 electrons.
In level 1 there is only one sub-level, which will be the s. In level 2 there are 2 sub-levels, the s and the p. At level 3 there are 3 sub-levels s, p and d. And at level 4 there are 4 sub-levels, the s, the p, the d and the f.
As in level 1 there is only the sub-level s, and this sub-level can only contain 2 electrons at most, then the first energy level can hold 2 electrons.
As in level 2 there is the sub-level s and p, and these sub-levels can only contain 2 and 6 electrons at most respectively, by adding them you get that the second energy level can hold 8 electrons.
As in level 3 there is the sub-level s, p and d, and these sub-levels can only contain 2, 6 and 10 electrons at most respectively, by adding them you get that the third energy level can hold 18 electrons.
The maximum number of electrons in each level can also be calculated by means of the expression: 2*n², where n is the level to which the electrons belong. Then:
You can see that you get the same amount of electrons, so either of the two ways of thinking is correct.
