Did you know that if you eat meat you are likely to be a liar, a cheat and a thief and be a violent person who commits sex crimes? This is a claim made in a book written by David S Podder called New Healthway (right) written for twelve year olds and published by S. Chand for use in Indian schools? Hopefully most people will treat this unsubstantiated outrageous claim with the contempt that it deserves. However it does illustrate the point forcefully that students and teachers must question the sources of their information, whether in a book or on the Internet, and not just accept what they read as incontrovertibly true.

It seems to me that there are four basic types of errors that can occur in books (or on Internet web pages). The first is all too common and is basically a publishing misprint. I know from my own experience that it is very difficult to eradicate all publishing errors, particularly in chemistry where the specific language is so important. It is not unusual to see CO² in newspaper articles on greenhouse gas emissions and the publishers of my Study Guide were initially insistent that since codeine and morphine have an ‘e’ on the end so should heroin!

The second is where the author has made a slip even though they obviously understand the subject. If I’m honest I seem to have a blind spot when it comes to arithmetical calculations and I know that occasionally even though all the steps of the worked solution are correct I sometimes get the final answer wrong. In chemistry books too sometimes an equation is not correctly balanced which suggests that the author has had a ‘forgetful’ moment.

The third type is more serious where the author clearly does not know the subject material well enough. If the reader checks in other books or articles they can easily find the correct chemistry elsewhere. There was an interesting example of this as a result of a question in the May 2012 Paper 1 Time Zone 1 Higher Level multiple choice examination. In question 7 the students had to identify the correct description of the acid/base nature of the oxides of chlorine, magnesium, silicon and sodium. The right answer correctly had SiO₂ as an acidic oxide but at least two teachers wrote in to complain. The response from the Chief Examiner in his May 2012 report is of interest. It states:

"Two respondents stated that silicon dioxide is actually amphoteric as cited in one textbook widely used for the current IB Chemistry Diploma programme. This statement in fact is incorrect in the textbook concerned as SiO₂ is actually classified as an acidic oxide. SiO₂ reacts with NaOH at T ~ 623 K, according to the equation SiO₂(s) + 2NaOH(aq) → Na₂SiO₃(aq) + H₂O(l). It is true that it does not react with water to form an acid. However, due to its clear reaction with sodium hydroxide it is classified as an acidic oxide."

I can breathe a sigh of relief that it is correct in my books but I have some sympathy with the authors of the offending book as it is very difficult to get absolutely everything correct when you write a book (or a web site!). If you look carefully you can find other errors in some of the IB text books currently on the market. What this does show is the importance of not relying on just one source for your information and teaching your students the skills of questioning everything - even if it is written in a supposedly reliable text book. One of the real advantages of the Internet as opposed to text books is that errors can be corrected immediately once they are spotted. I am certainly very grateful to those astute subscribers who have pointed out errors that I have made on this website.

The fourth type of error though is the most interesting one. This is an error which is perpetuated in most, if not all, chemistry books. It shows that people have stopped thinking and just repeat what they have learned or read in other books and thus continue to propagate false knowledge. There are several classic examples of this in chemistry. I have mentioned several on this site already, e.g. wrong statements in ionic bonding such as “sodium readily loses an electron to form a sodium ion” and diagrams that show the chlorine ion the same size as a chlorine atom etc. Another statement that needs careful thought is the accepted definition for oxidation and reduction in terms of electrons. The IB syllabus (Assessment statement 9.1.1) states “Define oxidation and reduction in terms of electron loss and gain” and virtually all chemistry text books state that oxidation is the loss of electrons and reduction is the gain of electrons. This definition obviously works when considering reactions such as the combustion of magnesium in oxygen. However get your students to look at this definition more critically by giving them an example such as the combination of nitrogen and hydrogen to form ammonia.

N₂(g)   +   3H₂(g)    ⇄  2NH₃(g)

Clearly this is a redox reaction as addition of hydrogen is one of the classic definitions of reduction.  The oxidation number of nitrogen has decreased from zero to – 3, so the nitrogen has been reduced and the oxidation number of hydrogen has increased from zero to + 1 so it has been oxidized. But what has lost or gained electrons?

In elemental nitrogen each nitrogen atom has five electrons and three pairs of electrons are shared between the two atoms to give a triple bond with each nitrogen atom having a share in eight electrons, with one pair acting as a non-bonding pair. According to the definition nitrogen should be gaining electrons when it is reduced. However in ammonia each nitrogen atom still has eight electrons surrounding it. Three pairs of electrons form single bonds with the three hydrogen atoms and there is one remaining non-bonding pair. Nitrogen has neither lost nor gained electrons. Some people might argue that the electrons have moved closer to the nitrogen nucleus thus stretching the definition of the word ‘gained’. It is certainly true that although the triple bond in nitrogen is a strong relatively short bond with a bond length of 0.110 nm according to the IB Chemistry Data Booklet the nitrogen to hydrogen single bond length is even shorter with a value of 0.101 nm. However moving closer is not really the same as ‘gained’, as in forming a negative ion. You can use a similar argument when burning hydrogen gas in oxygen gas as neither the oxygen nor the hydrogen atoms gain or lose electrons. It is possible to get electron transfer when oxidizing hydrogen with oxygen but only in a fuel cell. I just wonder whether originally the definition of oxidation was the loss of electrons in aqueous solution and over the years ‘in aqueous solution’ has got left out and the shortened version is just repeated in all the books as no-one stops to consider the validity of the definition anymore.