27
Ba
No. Atoms can gain and lose electrons but seldom gain or lose protons.
gain
Those electrons are the valence electrons. They are the electrons which mostly take part in exchange of electrons or sharing of electrons. Hence, valence shell electrons are a very important part of chemistry since all the reactions due to them only.
it gains one electrons to form I- ion
Fluorine tends to gain electrons
Yes.
Iodine only needs to gain one electron to become an anion.
They will loose electrons.
Metals lose electrons, nonmetals gain electrons.
Iodine tends to gain one electron when it forms an ion.
It gains three, loses five, or shares pairs of electrons
ions
They need to gain them.
Barium loses electrons to obtain a stable octet, like any other metal.
Magnesium is a group 2 metal and Iodine is group 7 so MgI2 because Mg needs to loose 2 electrons to gain a full outer shell and Iodine only wants 1 electron so there needs to be 2 Iodine atoms.