Organic Chemistry Chapter 1 - Organic Chemistry Chapter 1 1.1 LIFE AND THE CHEMISTRY OF CARBON COMPOUNDSWE ARE STARDUST Organic chemistry is the

Organic Chemistry Chapter 1 - Organic Chemistry Chapter 1...

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Organic Chemistry Chapter 1 1.1 LIFE AND THE CHEMISTRY OF CARBON COMPOUNDS—WE ARE STARDUST Organic chemistry is the chemistry of compounds that contain the element carbon. Carbon compounds are central to the structure of living organisms and therefore to the existence of life on Earth. We exist because of carbon compounds. 1.1 ATOMIC STRUCTURE The compounds we encounter in chemistry are made up of elements combined in different proportions. Elements are made up of atoms . An atom consists of a dense, positively charged nucleus. Nucleus contains protons and neutrons and a surrounding cloud of electrons. Protons have a positive charge (+) Electrons have a negative charge (-) Neutrons are electrically neutral Protons and neutrons contain nearly equal masses. Mass of an atom comes from the nucleus. The volume of the atom comes from the electrons. Elements commonly found in organic molecules are: o Carbon o Hydrogen o Nitrogen o Oxygen o Phosphorus o Sulfur o And some halogens: fluorine, chlorine, bromine and iodine. Each element is distinguished by its atomic number (Z), a number equal to the number of protons in its nucleus. The atomic number also equals the number of electrons surrounding the nucleus. 1.2A ISOTOPES The existence of atoms of the same element that have different masses. Mass= protons + neutron (protons is the atomic number, which is the same as the neutrons) Although all the nuclei of all atoms of the same element will have the same number of protons, some elements may have different masses because of the different number of neutrons Isotopes 1.2B VALENCE ELECTRONS Electrons that surround the nucleus exist in shells Each shell increases in energy and increases the distance from the nucleus Most important shell=valence shell Valence Shell: the outermost shell because electrons of this shell are the ones that an atom uses in making chemical bonds with other atoms to form compounds. The number of electron in the valence shell is equal to the group number of the atom. 1.2 CHEMICAL BONDS Ionic bonds: are formed by the transfer of one or more electrons from one atom to another to create ions. Covalent bonds: result when atoms share electrons. Octect Rule: tendency for an atom to achieve a configuration where its valence shell contains 8 electrons. 1.3A IONIC BONDS Atoms may gain and lose electrons and form charged particles ions. An ionic bond: attractive force of opposite charged ions. Electronegativity: measure of the ability of an atom to attract electrons. o Increases as you go across a horizontal row. Salts only form when atoms of very different electronegativities transfer electrons to become ions.
1.3B COVALENT BONDS AND LEWIS STRUCTURES Covalent bonds: form by sharing of electrons between atoms of similar electronegativities to achieve the configuration of a noble gas.

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