Chemistry and Chemists

Chemistry and Chemists

Let us start this article with a chemistry joke: Don’t trust atoms, they make up everything.

chemistry joke: Don't trust atoms, they make up everything.

What is chemistry, what do chemists do?

Chemistry is a science that describes the physical properties, composition, structure and reactions of matter.

To understand this definition more clearly we need to define some terms.

Matter – Anything that has mass and occupies space.

Atom – The smallest building block of matter.*

Molecule – Groups of atoms held together in a specific connectivity and shape.

* In reality atoms are made up of smaller building blocks called protons, neutrons and electrons.

Matter that contains only one type of atom is called an element, i.e. oxygen, nitrogen, carbon, gold, uranium, etc. All known elements are contained in the periodic table, and each is represented by a symbol.

Matter that contains combinations of elements in specific ratios is called a compound, for example:

  • Water (H2O) – contains two hydrogen atoms for every oxygen atom
  • Ethanol (C2H6O) – contains two carbon atoms and six hydrogen atoms for every oxygen atom
  • Sodium chloride (NaCl) – contains equal numbers of sodium and chlorine atoms

what do chemists do

Compounds can be described by their composition and structure.

Composition tells us the types of atoms that are present in a compound and the ratio of these atoms (for example H2O, C2H6O, etc.).

One property of pure compounds is that they follow the law of constant composition, that is they always have the same ratio of elements regardless of how the compound was made or where it came from. The elemental ratio maintained by pure compounds originates from the number of each type of atom contained in a molecule of that compound.

Structure tells us which atoms are connected (bonded) to each other, how far apart they are, and the shape of the molecule.

Physical properties are the identifying characteristics of matter. Some properties can be readily measured with our senses, such as odor and color, instruments are needed to measure other properties, such as electrical resistivity, compressibility, hardness, melting point, etc.

Chemical properties describe the reactivity of a substance. Examples include: “ethanol burns in air”, “sodium reacts vigorously with water”, corrosion of metal parts (rust), the physiological effect of a drug, etc.

What’s the chemical name for a drug?

Over view of Generic drugs and drug naming.

Drugs often have several names,which describes the Atomic or molecular structure of the drug,The chemical name is this usually too complex and cumbersome for general use.

Chemical nomenclature:

is a set of rules to generate systematic names for chemical compounds ,The nomenclature used most frequently world wide is the one created and developed by the international union of pure and applied chemistry (IUPAC).

The (IUPAC)rules for naming organic and inorganic compounds are contained in two publications known as the blue book and the res book,respectively,the third publication,known as the green book ,describes the recommendations for the use of symbols for the physical quantities .(in association with the IUPAC),while a fourth ,the gold book ,contains the definitions of a large number of clinical terms used in chemistry.

Similar compendia exist for biochemistry (the white book ,in association with IUBMB) analytical chemistry (the orange book) macromolecular chemistry (the purple book)and clinical chemistry (the silver book) these “color books “are supplemented by shorter recommendations for specific  circumstances that are published periodically in the journal pure and Applied chemistry.

Aims of chemical nomenclature:

The primary function of chemical nomenclature is to ensure that a spoken or written chemical name leaves no ambiguity concerning which chemical compound the name refers to: each chemical name should refer to a single substance. A less important aim is to ensure that each substance has a single name, although a limited number of alternative names is acceptable in some cases.

Preferably, the name also conveys some information about the structure or chemistry of a compound. CAS numbers form an extreme example of names that do not perform this function: each CAS number refers to a single compound but none contain information about the structure.

The form of nomenclature used depends on the audience to which it is addressed. As such, no single correct form exists, but rather there are different forms that are more or less appropriate in different circumstances.

A common name will often suffice to identify a chemical compound in a particular set of circumstances. To be more generally applicable, the name should indicate at least the chemical formula. To be more specific still, the three-dimensional arrangement of the atoms may need to be specified.

In a few specific circumstances (such as the construction of large indices), it becomes necessary to ensure that each compound has a unique name: This requires the addition of extra rules to the standard IUPAC system (the CAS SYSTEM )is the most commonly used in this context), at the expense of having names that are longer and less familiar to most readers. Another system gaining popularity is the international chemical Identifier (InChI) – which reflects a substance’s structure and composition, making it more general than a CAS number.

The IUPAC system is often criticized for the above failures when they become relevant (for example, in differing reactivity of sulfur  allotropes , which IUPAC does not distinguish). While IUPAC has a human-readable advantage over CAS numbering, it would be difficult to claim that the IUPAC names for some larger, relevant molecules (such as rapamycin) are human-readable, and so most researchers simply use the informal names.

Nevertheless as a result ,due to the complex names of chemistry drugs and chemical,the scientists made a system that called IUPAC .

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