A. N, O 2- , F –

B. Sc 3+ , Y 3+, La 3+

C. Cl -, Ar, Ca 2+

D Cr, Cr 2+, Cr 3+

Please explain

### 3 Answers

Well, an unionised atom has the same number of electrons as protons in its nucleus. The number of protons is given by the atomic number in the periodic table. So just look at the periodic table and you have the number of electrons in unionised atoms. If you ionise an atom (add or remove electrons), then you give it some charge. Cl – for example has been given an extra electron to make it negatively charged. This means instead of having 17 electrons, it now has 18.

This question has been made easy really. It could be a lot more difficult. D can be instantly ruled out, because Cr has two more electrons than Cr 2+.

So you just work through them. O 2- has 8 + 2 = 10 electrons, N only has 7, so A is wrong, without even considering F-.

Sc 3+ can’t have the same number of electrons as Y 3+ or La 3+, because they are different types of atoms. They all started off with different numbers of electrons and the same number of electrons has been removed, so they still have different numbers of electrons.

Part C is therefore the only answer left. But just to check, let’s calculate how many atoms each has. Cl has 17 atoms normally, so Cl- has one more, to make 18. Ar has 18 normally, so that’s how many it has in this case. Ca has 20 normally, but two have been removed to make it 2+, so you have 18.

C is the answer.

D…Cl(1-) ; Ar ; Ca(2+)

Each will have 18 electrons.

not sure the place Soc got here up with one hundred… yet.. it is greater of a conceptual subject count number. the assumption is the state of count number is with the help of debris having adequate kinetic potential to triumph over intermolecular forces of attraction. the occasion of a million particle is neither good nor liquid nor gas is an occasion used to coach the theory section modifications contain overcoming intermolecular factors of interest. there is truly a “variety” of debris that unexpectedly defines a factor. so the excellent thank you to reply to it is…. (a million) section modifications contain intermolecular factors of interest (2) KE vs intermolecular forces defines the section, (3) you won’t be in a position to have intermolecular forces with a million particle.