THE CHEMISTRY OF LIVE
Everything around us is made up solids, liquids or gases. Despite their obvious differences in physical apperance, they are all made up of matter and share the same basic structure. Matter is anything that has weight and takens up space. All matter is composed of basic structure called elements. An element is a substance is a substance that can not be broken down to other substances by chemical reactions. Today 111 elements are known, although naturally occouring elements on earth only 92 of them, gold, copper, carbon, mercury and magnesium are examples. They have their own symbol, usually the first letter or two of its name. Some of the symbols are devined from latin or German names; for example, the symbol for sodium is Na, from latin word Natrium. Elements mostly exist in a mixture or chemical combinations but some of them exist in a pure form.
Bioelements
Living organisme require about 25 chemical elements. They are called bioelements, which are essential to life. Just four of these, oxygen, carbon, hydrogen, nitrogen, make up 96% of living matter. Phosphorus, sulfur, calcium, potassium, and other elements make up 4% of living matter. Some bioelements are required by an organism in only minute quantities, these are called trace elements. Iron, cobalt, copper and lodine are examples. (Table-1.1). Elements in the human body
Organisation Of Matter
Atoms
Elements are composed of atoms. An atoms is the samallest unit of matter. Atoms of an element are similiar to each other, but they differ from the atoms of any other elements. Atoms are very small; they can be seen only strong electron microscope.
Structur of Atoms
All atoms are comprised of a nucleus containing protons and neutrons with electrons spining around them. The overall change on the nucleus at the centre of this ‘miceoscopic’solar system is positive due to the presence of positivelly charged protons, and neutrons which carry no charge. (Table-1.2). Negativelly charged electrons orbit around them balancing the positive charge or protons. The number of electrons plays an important role in determining the characteristics of an atom. If there are more electrons than protons, the atom will be overall negative and consequently unstable. (Figure-1.1).
No | Elements | Symbol | Approximate % |
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. | Oxygen Carbon Hydrogen Nitrogen Calcium Phosphorus Potassium Sulfur Sodium Chlorine Magnesium | O C H N Ca P K S Na Cl Mg | 65.0 18.5 9.5 3.3 1.5 1.0 0.4 0.3 0.2 0.2 0.1 |
No | Elements | Symbol | Approximate % |
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. | Chromium Cobalt Copper Fluorine Iodine Iron Manganese Zinc Silicon Tin Vanadium Selenium | Cr Co Cu F I Fe Mg Mo Si Sn V Se | Together less than 0.1 % |
Electrons and energy
Electrons are constantly revolving around their nucleus within orbits. Since there are many orbits in which electrons can move, they may be found at varying distances from the cental nucleus. Those electrons in orbits that are far from the nucleus have more potential energy than those electrons in orbits close to it. This can be understood by considering the position of a stone.
When the stone is on the ground it has no potential energy. However when it is lifted it gains poteintial energy. This is lost when the object returns to its original position. In the same way, an electrons can gain energy from heat or light and can move into a position in an orbit fruther away from the nucleus. This energy is released when it returns to its original position. (Figure-1.2).
The ability of electrons to gain or lose energy according to their position is extremely important for energy transfer on earth. For instance, radiant energy can excite electrons in green plants and algae, moving them into a higher orbit. This energy is then transferred as chemical bond energy in photosynthetic organisms such as green plants and algae.
Atomic Weight
The atomic weight of an element describes the number of protons and neutrons within its nucleus. For example, the smallest atom hydrogen is composed of only a single electron and single proton.
Atomic Number
The atomic number is the number of protons in each element. Each element has unique number of protons. In unchanged atoms the number of protons is equal to number of electrons.
Mass Number
Mass number is the sun of protons plus neutrons in the nucleus of an atoms. The number and ratio of subatomic particular elements is a factor that determines whether it is stable or unstable. If the numbers of protons is equal to the number of neutrons and electrons, it is termed as stable and uncreative. If the number differs, atom is unstable, reactive and capable of changing its form, probably taking on the properties of an atom of another elements as a result.
Isotopes
If the number of neutrons in a particular elements differs even though the member of protons and electrons remains the same, this type of element is termed an isotope. The chemical properties of an isotope of oxygen for example, are identical to normal oxygen but are physically different in that they are heavier due to the extra neutrons within their nucleus. Thus an isotope has a greater atomic mass. Two other examples of isotopes are nitrogen and carbon.
N14 normal element, N15 isotope
C12 normal element, C11, C14, C13 isotope
Isotope are frequently used in biological research. The uptake of an isotope can be detected and its activity in subsequent reactions monitored. The rediation produced by some isotopes is frequently used recombinant DNA techniques to follow changes in DNA structure.
Particle | Symbol | Function | Location | Mass | Charge |
Electron Proton Neutron | e- P n | Bonding Identity Isotope | Orbitals Nucleus Nucleus | 0 1 1 | - + 0 |
Compounds and molecules
A compound is a substance consisting of two or more elements combined in a fixed ratio. A molecule is the smallest unit of a element. For example; water consists of hydrogen and oxygen elements in a2 : 1 ratio. Another example is table salt, the combination of chloride and sodium in a 1 : 1 ratio. Formation of a compound changes the characteristic of elements. Pure sodium is a metal and pure chloride is a poisonous gas, they from edible table salt.
Formation Of Chemical Bonds
Atoms are combined to from molecules to from molecules by chemical bonds. The number electrons in an atom’s outermost shell, or valance electrons determinants which type of chemical bond can form. (Table-1.3). Atoms have a tendency to fill their outermost orbit with electron. The achieve this, they interact with another atomto donate, receive or share electrons. This result of an association between two or more atoms is a molecule. The component atoms of compound in biological system are heid together by three main types of bonds.
Ionic Bonding
Ionic bonding is a chemical bond formed between ions as a result of the attraction of opposite electrical charges. Most atoms complete their orbitals by gaining or losing electrons. For instance, a Cl atom has 7 electrons in its outermost orbital and requires one extra electron to complete it. If it receives one, it becomes a negatively charged ion and is abbreviated as (Cl-). If Na and Cl atoms react, one electron is donated from the Na and Cl atom. The Na atom is now a positive ion after losing one electron. Since opposite charges attract each other, an electrostatic or ionic bond forms between negatively charged and positively charged ions.
Covalent Bonding
A type of strong chemical bond formed by the sharing of one or more pairs of electron. Most atoms have an incomplete outermost orbital and must gain or donate one or more electrons to become stable. Since the energy needed for this is considerable, instead two or more nonmetalic atoms group together and share their outermost electrons.
Type | Formed | Strength | Example |
Ionic Bonds Covalent Bonds Hydrogen Bonds Van Der Walls Attractions | When one atom donated an electrons to another When atoms share their electrons pairs When negative charged atoms attract hydrogen atom When oppositely charged regions of molecules attract one another | Weak in water Strong Weak Weak | Table salt CH4 Water Protein |
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