Chemistry

The interaction between atoms that leads to a rearrangement of the electron to a more stable state is what we define as a chemical bond. All atoms, except those of the noble gases*, readily engage in chemical bonding either with atoms of their own kind (in elements) or with atoms of a different kind (in compounds). 3 Types of chemical bonding: Ionic bond - electrostatic forces hold together oppositely charged ions. Covalent bond - two atoms sharing electron pair(s). Electrons are mutually attracted by the nuclei of adjacent atoms. Metallic bond -is a complicated type of bond. At the simples level metal atoms are envisaged of being metal cations in a “sea” of electrons. The electrons are shared between all the ions simultaneously. A better description of metals is obtained from the band theory. Ionic bond: Ionic bonds form between oppositely charged ions, generally, but not always, between metals and non-metals. Metals versus Nonmetals: Metals are conductors...

Positive Ions  (Cations) : a) Cations formed from metal atoms have the same name as the metal, e.g. Na+ is the sodium ion b) If a metal can form different cations, the positive charge is indicated by a Roman numeral in parentheses following the name of the metal, e.g. Au+ is the gold(I) ion and Au3+ is the gold(III) ion. c) Cations formed from nonmetal atoms have names that end in -ium, e.g. NH4+ is the ammonium ion. Some examples of cations that you might encounter: Negative Ions  (Anions) : a) The names of the monatomic anions are formed by replacing the ending of the name of the element with -ide, e.g. O2- is the oxide ion. b) Polyatomic anions containing oxygen (called oxyanions) have names ending in -ate or -ite, e.g. SO 4 2- is the sulfate ion and SO 3 2- is the sulfite ion. c) Anions derived by adding H+ to an oxyanion are named by adding the prefix hydrogen or dihydrogen, e.g. HCO3- is the hydrogen carbonate ion More on naming oxyanions: ...

Atomic weights : For chemists who need to know the atomic weight of all elements precisely this means the masses of all elements even the mass of every isotope needs to be determined by experiment. This is done in a mass spectrometer which can measure the mass and the abundance of the different isotopes. All masses are compared to the mass of a 12C atom and reported as average relative atomic masses of all naturally occurring isotopes of that element. Magnesium for example has a relative atomic Mass of 24.305 which means it is 24.305/12.00000 = 2.025 times heavier that a 12C atom. To use relative atomic masses in calculations we can do one of two things.  We can express the mass of one atom by adding the unit u (atomic mass unit) to the value of the relative atomic mass. E.g. 24.305 u is the mass of one magnesium atom which equals 24.305 x 1.6605E-24 g or we add the unit g/mol to the relative atomic mass and get the mass of a mole of magnesium atoms in g (24.305 g/mol...

Dalton's Atomic Theory: Some basic laws that have been established by the year 1800: Law of definite composition (Berzelius):  Every pure compound has a constant composition. Laws of conservation of mass (Lavoisier):  Matter can neither be created or destroyed during a chemical change. Dalton's Laws: All matter is composed of extremely small particles called atoms. All atoms of a given element are alike, but atoms of one element differ from atoms of any other element. Compounds are formed when atoms of different elements combine in fixed proportion. A chemical reaction involves a rearrangement of atoms. No atoms are created or destroyed or broken apart in a chemical reaction. The law of definite composition is explained by the third statement. Water (H 2 0) is always formed by two atoms of hydrogen joining with one atom of oxygen. Its elemental composition never changes, no matter were it was from or how it was synthesised.  The fact that chemical ch...