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what is an acidic radical and a basic radical?
Acid radical:
Acid radical is an anion left after removal of hydrogen atoms from an acid.

Anions :

Anions are atoms or groups of atoms that have gained electrons. Having more negatively charged electrons than positively charged protons, they are negatively charged. The atoms that form ions most easily are the Group 17 (or VII) atoms, also called the halides: F, Cl, Br and I. All these form anions with a -1 charge. O, S, N and P also form anions, carrying charges of -2 (oxygen and sulfur) or -3 (N and P). 

Most anions are composed from multiple atoms, and are called polyatomic ions (polyatomic = many atoms). Polyatomic ions are usually built around a core atom which is more often than not a non-metal, but some metals, notably manganese and chromium, form polyatomic ions as well. In most polyatomic ions, these atoms combine with oxygen and sometimes with hydrogen as well. As with every other generalisation, there are exceptions. For example, SCN-, the thiocyanate ion, is polyatomic, but has neither oxygen nor hydrogen. (Worse, NH4+ is polyatomic, but is a cation!) But back to the story. 

The negative charge (the extra electron) in the polyatomic ion is shared around the entire ion. It is not associated with a particular nucleus in the ion, specifically not with the nucleus to which oxygen and/or hydrogen are attached. This is true whether the charge is single or multiple. 

COMMON NEGATIVE IONS (ANIONS) 

acetate CH3COO-
nitride N3-

bromide Br-
nitrite NO2-

carbonate CO32- 
oxalate C2O42-

hydrogen carbonate HCO3-
oxide O2-

chlorate ClO3-
permanganate MnO4-

perchlorate ClO4-
phosphide P3-

chloride Cl-
phosphate PO43-

chlorite ClO2-
(mono)hydrogen phosphate HPO42-

hypochlorite ClO-
dihydrogen phosphate H2PO4-

chromate CrO42-
sulphate SO42-

dichromate Cr2O72-
hydrogen sulphate HSO4-

cyanide CN-
sulphide S2-

fluoride F-
hydrogen sulphide HS-

hydride H-
sulphite SO32-

hydroxide OH-
hydrogen sulphite HSO3-

iodide I-
thiocyanate SCN-

nitrate NO3-
thiosulphate S2O32-

Note that, with the exceptions of hydroxide (OH) and cyanide (CN-), all the names ending in -ide are monatomic. The rest are -ates or -ites. In the days of yore, chemists gathered samples of anions and then tried to give them some order. The rules they came up with went like this: 

The most frequently occurring version of a polyatomic ion got the name -ate. The most frequently occurring anion of chlorine and oxygen is ClO3-. It was given the name chlorate. 
One more oxygen? Put a per- on the front. ClO4- is perchlorate. (Per is from the Greek hyper for too much.) 
One less oxygen? Change the name to -ite. ClO2- is chlorite. 
Two less oxygens? Put a hypo- on the front. ClO- is hypochlorite. (Hypo is from the Greek for too little or not enough.) 

So from above discussion we see that all acid radicals are anions but all anions are not acid radicals.

Basic radical :
The basic radical is the cation left after removal of OH or other alkaline group from the bases.

Cations :
Cations are atoms that have lost an electron to become positively charged. Sodium has one valence electron, one electron in its outer energy level, so tends to lose one electron, and to become an ion with a +1 charge. The same could be observed for lithium, potassium, rubidium, caesium and francium. Magnesium, along with the other elements in group 2 of the periodic table, has two valence electrons, so tends to become an ion with a +2 charge. Aluminium tends to become +3. 

What about the transition metals like lead, copper, tin and manganese? Electrons in the transition elements are packed in a way that, generally, places the additional electrons inside the outer energy level. Iron has six more electrons than calcium, but the additional electrons have less energy than the two on the outer. The transition elements tend to have either one or two loosely held (valence) electrons. The six electrons present in iron but absent in calcium are held much less loosely than those in the next level down, but more tightly than those in the outer level. Having removed two electrons from both iron and calcium, removing a third electron would be much, much, much harder from calcium than from iron, since calcium's next electron is both more tightly held (a lower energy level) and in a complete shell. 

Because of this ambiguity in the transition elements, it is sometimes hard to predict the charge for their corresponding cation. Copper, for example, frequently loses two electrons (Cu2+), but copper ions with a +1 charge (Cu+) are also well known. Tin most often looses two (Sn2+), but frequently loses four (Sn4+). Iron can lose two or three. Manganese? So many choices you don't want to know. 


For our purposes you will be able to tell which ion you are dealing with by the context it occurs in. You may be given the name of the ion. Sn2+ is named tin(II) [pronounced "tin-two"]. Pb4+ is named lead(IV). 

You may be given a formula including the ion. FeCl2 is called iron(II) chloride [iron two chloride], containing Fe2+. (Each of the chlorides have accepted one electron, similar to other Group VII elements.) FeCl3 is called iron(III) chloride, containing Fe3+. 


Thus all basic radicals are cations but all cations are not basic radicals.


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