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Neurology is a medical specialty dealing with disorders and diseases of the nervous system. In the past the term has been used more generally for the study of the nervous system; the term itself comes from the Greek νεῦρον, neuron, for "nerve cell" and the suffix -λογία for "study of." However, today the term neuroscience is employed for the larger field that encompasses the scientific study of the nervous system, while neurology is the branch related to medicine. Both neurology and neuroscience are interdisciplinary fields.
Neurologists in the United States
In particular, the human brain is the most complex known living structure, with some 86 billion nerve cells and trillions of neuronal connections; millions of information transfer processes take place in remarkable coordination every second in the human central and peripheral nervous system. There also are more than 1,000 disorders of the human brain and nervous system, with neurological disorders affecting up to one billion people worldwide.
The main group elements of the periodic table are groups 1, 2 and 13 through 18. Elements in these groups are collectively known as main group or representative elements. These groups contain the most naturally abundant elements, comprise 80 percent of the earth's crust and are the most important for life. Economically the most produced chemicals are main group elements or their compounds. It is in the main group elements that we most clearly see the trends in physical and chemical properties of the elements that chemists have used to understand the "stuff" things are made of.