Question

Name a cation or a radical with valency '2'?

Answer 1

An anion is a negatively charged ion with more electrons than protons, whereas a cation is a positively charged ion with less electrons. Cations and anions are attracted to one other by their opposing electric charges and easily form ionic compounds. A radical is an atom, molecule, or ion with an unpaired valence electron in chemistry. These unpaired electrons make radicals very chemically reactive, with a few exceptions. Many radicals dimerize on their own. The majority of organic radicals have a limited life span.

Complete answer:
First and foremost, let's define valency.
You might be wondering what valency is. The number of outside electrons in any element or cation may be measured by counting the number of outer electrons, also known as valence electrons. The number of outer electrons is simply the valency of an element or cation if the number of valence electrons is less than or equal to 2. If the number of valence electrons is more than 2, the valency of the element or cation may be calculated by subtracting 8 from the number of outer electrons.
Strontium 2+ is a cation of the element strontium in this case. Strontium must lose two electrons since its charge is two positive. Because its atomic number is 38, it has 36 electrons. This is due to the fact that it possesses 38 electrons at the start. To become 2+, it loses two electrons. As a result, 38 minus 2 = 36. When you know how many electrons a cation has, you may use the technique above to determine its valency. (For reference, if an element or cation has fewer than or equal to two valence electrons, its valency is just the number of outside electrons.) If the number of valence electrons is more than 2, the valency of the element or cation may be calculated by subtracting 8 from the number of outer electrons.)
We know that the first shell of an atom must have two electrons, the second shell must have eight electrons, the third shell must have eight electrons, and so on, according to Bohr's model. To get to the outer shell, subtract the number of electrons in the atom from the number of electrons in the shells.
Strontium 2+ has a total of 6 shells in this example. It possesses two electrons in the first shell. It contains 8 electrons in the second shell, and so on until the sixth cell, which has 2 electrons. Because 2 is less than or equal to 2, strontium 2+ has a valency of 2.
As a result, $S{{r}^{2+}}$ is a cation with the valency '2'.

Note:
The IUPAC defines valence as the maximum number of univalent atoms (initially hydrogen or chlorine atoms) that can combine with an atom of the element under discussion, a fragment, or be replaced for an atom of this element.
The amount of hydrogen atoms that can mix with an element in a binary hydride, or twice the number of oxygen atoms that can react with an element in its oxide or oxides, is an alternate contemporary definition.
Because an element can have more than one valence, this definition differs from the IUPAC definition.