chemistry revision chapter 1 pt 2

chemistry revision chapter 1 pt 2

1. Sub atomic particles

   • the atomic number is the number of PROTONS and NEUTRONS
   • The atomic MASS number of an atom is the total number of protons and neutrons in an atom
   • Most elements have two or more isotopes
   • Ar=(mass of first isotope % of first isotope) + (mass of first isotope % of second isotope) all over 100

2. electronic structure

   • Electrons occupy shells around the nucleus. the electron shell nearrest to the nucleus takes up to 2 electrons
   • the peridoic table is arranged in order of proton number
   • the electronic structure of each of the first 20 elements can be worked out using the atomic number of the element and the maximum numberr of the electrons in each shell

3. developing the periodic table

   • In 1865 John Newlands noticed that when Dobereiner had put the elements in the wrong places.
   • John Newlands saw a pattern where there were similar properties every 8 elements he called this theory the 'law of octaves '.
   • 1869 Dmitri Mendeleev decided to swap some elements round so that the patterns of chemical behaviour fitted better, imagine some of the undiscovered elements and decided to leave gaps in the periodic table to fit these elements
   • in 1907 Mendeleev died and didn't see the discovery of sub-atomic particles to be discovered which gave the final evidence allowing the modern periodic table

4. comparing metals and non metals

   • metal properties: lustrous, hard, high density, high tensile strength, high melting point and boiling point, good conductors of heat, and good electrical conductor
   • non metal properties: dull, soft brittle or gas, low density, low or no tensile strength or gas, low melting point and boiling point, poor or no thermal conductivity, and poor or non conductivity of electricity.
   • chemical properties of metals are the result of reactions with oxygen or acids

5. metals and non-metals

   • metals are on the left side of the periodic table and non metals are on the right
   • magnesium and any other metals is a metal because of its atomic structure.

6. the outer electrons

   • all other atoms are less stable. their electrons move or share with other electrons to try become as stable as the atoms with 8 electrons in their outer shell.
   • If an atom has one or two electrons in its outer shell these electrons will transfer out. This forms a positive ion
   • If an atom has six or seven electrons in its outer shell, electrons from other atoms will add in the 'spaces' to make up an outer shell. This forms a negative ion
   • Some elements are more reactive than others. this can be because their outer electrons transfer more easily than others or transfers in more easily than others

7. exploring group 0

   • all the elements of group 0 in the periodic table have 2 things in common: they are all unreactive, and they are all gases
   • the elements in group 0 do not generally make compounds with other elements.
   • they do not make compounds because the atoms have 8 electrons in their outer shell.