# The formula of the compound is #A_2B_5#. The number of electrons in the outermost orbits of A and B respectively are?

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- 6 and 3
- 5 and 6
- 5 and 2
- 2 and 3

- 6 and 3
- 5 and 6
- 5 and 2
- 2 and 3

##### 1 Answer

'2. 5 and 6

#### Explanation:

In a neutral (uncharged) molecule, the sum of the bonding valence electrons must be equal. So, the products of the negative element and its charge and the positive element and its charge must be equal.

If we have 2 "A" atoms and 5 "B" atoms we have:

To be equal,

This actually refers to the "charge" of the ion. The "number of electrons in the outer shell" would depend on the specific element, and if the ion form is intended, then the correct value would be the positive ions charge *less* and the negative ions *added* to the existing ones.

So, if we have

In that case, the number of electrons in each atoms' shell would be:

Answer 2.