6 ANATOMY FOR NURSES [Chap. I 



prepared in the laboratory, this theory was abandoned, but the 

 distinctive terms organic and inorganic persisted. Under the 

 present classification organic compounds are compounds that con- 

 tain carbon. 



Because of the fact that there are numerous carbon compounds and 

 also because many of these can be grouped into classes with weU-defined 

 characteristics, the study of the carbon compounds has become a separate 

 phase of the general study of chemistry and is called organic chemistry. 



SOME CHEMICAL TERMS 



Atom. — An atom is the smallest part into which an element 

 can be divided. Atoms are alike for the same element, but 

 different for different elements. 



Molecule. — ^ A molecule is a group of atoms in chemical com- 

 bination. Compounds are made up of multitudes of molecules, 

 all of which are alike for the same compound. 



Chemical formula. — A chemical formula is a simple means 

 for representing the composition of the molecule. Symbols are 

 made use of to represent the elements and small subscript figures 

 to represent the number of atoms of the respective elements. 

 For example, the formula for the sulphuric acid molecule (H2SO4) 

 shows it to be made up of two atoms of hydrogen, one atom of 

 sulphur, and four atoms of oxygen ; the formula for the sodium 

 chloride molecule (XaCl) shows it to be made up of one atom of 

 sodium and one of chlorine. 



Chemical equation. — A chemical equation is a simple means 

 for representing the matter change that takes place in a chemical 

 action. When carbon burns it combines with oxygen to form 

 carbon dioxide. The equation that expresses this, 



C + O2 -> CO2, 



tells that during the process of combination, one atom of carbon 

 combines with one molecule of oxygen (composed of two atoms) to 

 give one molecule of carbon dioxide. In the action of sodium 

 hydroxide with hydrochloric acid, water and sodium chloride are 

 formed. The equation to represent this, 



NaOH + HCl -> H2O + NaCl, 



shows that one molecule of sodium hydroxide reacts with one mole- 



