[Hello123]

Identify the element which can form ions with the same electron arrangement as argon?

Is it :

1. Oxygen
2. Calcium
3. Aluminium
4. Sodium
5. Magnesium
6. Fluorine

I really don't understand, could you please explain it. You don't need to give me the answer, just lead me in the right direction.

Thanks if you *delete me*

[Arkcon]

Great.  What is the electron arrangement of argon?  You can find it in many places, often textbooks list the electron arrangement of each element, in a list table or in the periodic table.

[EmmaCole]

Argon has an atomic number of 18, with an electronic configuration of 2,8,8. I think the answer is sodium.

[CKabes]

If you type in on google "Electron Configuration of Argon" this comes up:

1s2 2s2 2p6 3s2 3p6

I'm not an expert, but I would guess it's Calcium which has an electron configuration of:

1s2 2s2 2p6 3s2 3p6 4s2

Lets remember, Calcium is a cation, freely giving away 2 electrons. If you got rid of Calciums two valence electrons, you would have:

1s2 2s2 2p6 3s2 3p6

[fledarmus]

Look at your periodic table. All of the elements would like to have the same electron configuration as a noble gas, because those are the stable electron configurations. For elements that are just one or two spaces to the left of the noble gases, they can do it by gaining one or two electrons. For elements that are on the far left side of the periodic table, they can do it by losing one or two electrons.

So if you take for example, Neon (atomic number 10), the element to the left of neon is fluorine, and if it gains one electron (F^-), it has the same electron arrangement as neon. If you look at the far left of the table and down one row, you get sodium (atomic number eleven), which if it lost one electron (Na⁺) would have the same electron configuration as neon.

The atomic number is the number of protons an element has, as well as the number of electrons. To get the same electron arrangement as a noble gas, it merely needs to gain or lose the number of electrons that would give it the same number as the nearest noble gas.