Chemistry: The Periodic Table
- Created by: William Page-Brown
- Created on: 09-04-13 17:12
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- Chemistry: the periodic table
- the history of the atom
- plum pudding model, bohr model, nuclear atom
- theories are adapted through time
- atoms
- nucleus contains protons and neutrons
- nucleus has a positive charge from protons
- electrons have no mass and are negative
- protons = electrons
- mass number - protons and neutrons
- atomic number - protons
- neutrons = atomic / mass
- elements and isotopes
- order of ascending atomic number
- number of electrons in outer shell = group
- isotopes have the same atomic number but different mass numbers
- history of the periodic table
- dobereiner organised elements into triads
- newlands octaves put elements into rows
- dmitiri mendeleev aranged elements with spaces for undiscovered
- electron shells
- electrons always occupy shells
- 1st. 2 electrons 2nd. 8 electrons 3rd. 8 electrons
- configuration2,8,8 = 12 =Mg
- ionic bonding
- atoms lose of gain electrons
- attracted by opposite charges
- metals and non metals form giant ionic structures
- do not conduct electricity when solid
- ions and ionic compounds
- metals lose electrons to form positive ions
- non metals gain electrons to form negative ions
- non metals and a metal form an ionic bond
- if 2 electrons lost, charge is 2+
- dot and cross shows ionic bonding
- covalent bonding
- covalent bonds share electrons
- hydrogen atoms share electrons with one another
- carbon teams up with four hydrogens
- chlorine atoms share electrons with one another
- water is oxygen covalently bonding with two hydrogen atoms
- carbon dioxide is one carbon and two oxygen atoms
- alkali metals
- lower in group 1 - more reactive elements
- more reactive due to easily lost electron
- properties: low melting point, low density, very soft
- oxidation is the loss of metals
- alkali metals oxidize because they only have one outer electron
- lithium - red flame
- sodium - orange flame
- potassium - lilac flame
- halogens
- fluorine, chlorine, bromine, iodine, astatine
- as you go down, less reactive elements
- chlorine: reactive, poisonous, dense green gas
- bromine: dense, poisonous, orange liquid
- iodine: dark grey crystalline solid
- reduction is the gain of electrons
- halogen + alkali = salt
- metals
- all metals have same basic qualities
- held together by metallic bonds
- movement of free electrons
- very hard, dense, and lustrous
- high melting and boiling points
- strong yet malleable
- good conductors of heat and energy due to free electrons
- superconductors and transition metals
- all metals have some electrical resistance
- if a metal is made cold enough the resistance dissapears
- could start a current and need no energy
- disadvantages: expensive to produce cold temperatures, cannot make room temperature
- transition metals are in the centre of the periodic table
- transitions make good catalysts
- thermal decomposition and precipitation
- when a substance breaks down due to heat
- transition metal carbonates break down
- a precipitate is an insoluble substance formed in a liquid
- precipitation is a test for transition metal ions
- copper oxide - blue
- iron oxide - grey/green
- iron hydroxide - orange/brown
- water puroty
- limited water resources in UK: surface water, ground water
- water is purified in treatment plants
- filtration - wire mesh
- sedimentation - chemicals added to remove clumps
- chlorination - gas to kill bacteria
- tap water may contain: nitrate, lead, pesticide residues
- testing water puroty
- 1) add hydrochloric acid
- 2) add ten drops of barium chloride
- 3) white precipitate means sulfate ions
- 1) add nitric acid
- 2) add ten drops of silver nitrate
- 3) any precipitate means halide ions
- the history of the atom
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