Chemical bases of life Rosendo 10-B

Matter It is defined as everything that has weight and occupies space. Everything that makes up life and what is not alive is made of matter. Matter is made of pure substances called elements and these in turn are made of particles called atoms.

Chemical element Substance that can not be decomposed or divided into simpler substances by ordinary chemical means. On earth, until now, the existence of 100 chemical elements has been determined. The scientists assign to each element a chemical symbol that usually corresponds to the first letter or the first two letters of its name in Spanish or Latin.

Most important elements in the human body Oxygen Carbon Hydrogen Nitrogen

Atomic theory Democritus (460-370 BC). Greek philosopher. Of the first to postulate the atomic theory. He pointed out that the "arké" or atoms were the indivisible and that all reality was composed of two unique elements: the vacuum and the atoms. These particles move continually in a vacuum and, according to their shape and size, constitute the main physical bodies.

Modern Atomic Theory The modern atomic theory is based on the models of Dalton, Schrodinger and Bohr. This theory was developed during the nineteenth and twentieth centuries A nucleus with positive charge and negatively charged particles surrounding it.

atom It is the smallest portion of an element that retains the chemical properties of it. Special techniques of scanning electron microscopy with up to five million times of amplification have allowed researchers to photograph the positions of some large atoms in the molecules that contain them.

Atomic model Scientists have discovered several subatomic particles but by the end of this course we will consider three: Electron: particle with negative charge, with a tiny atomic mass and located in regions outside the atomic nucleus called orbitals. Electrons play a very important role in the chemical reactions of the elements.

Atomic model Proton: positive charge, each element has a fixed number of protons that is called the atomic number and is written to the lower left of the chemical symbol 8O. The protons are located in the atomic nucleus. The mass of the proton is 1 unit of atomic mass or Dalton.

Atomic model Neutron: particle without charge. Located in the atomic nucleus. The mass of the neutron is 1 unit of atomic mass or Dalton. The number of neutrons in an atom can vary, varying its atomic mass giving origin to the so-called isotopes. Isotopes are very useful in biology, which will be discussed later.

Atomic mass The mass of an atom is extremely small when compared to the mass of any object visible to man. To express it numerically Dalton has been designated as a unit of atomic mass (uma). This is done in honor of John Dalton; chemist who postulated the atomic theory at the beginning of the 19th century. One atomic mass unit equals the approximate mass of a proton and a neutron.

Periodic Table Classifies elements based on the properties in families and groups. Established by Dimitri Mendelev Main groups: Alkaline Metals Alkaline earth Metals Noble gases Transition metals Other

Elements of biological interest Oxygen Carbon Hydrogen Nitrogen Calcium Phosphorus Potassium Sulfur Sodium Magnesium Clorox Iron

Molecular formula Indicates the composition of the substance in question and the number of atoms present.