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The Periodic Table Chapter 12
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The modern periodic table Arranged by atomic number NOT atomic mass. Atomic number: Number of protons New elements are still being discovered, but most have very short half-lives Vertical = Groups: Families of Elements that share properties. They have the same number of electrons in outer shell and this determines their reactivity. Periods: are the horizontal rows and the atomic number increases as you go from left –right.
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Metals and Non-Metals
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Metals and Non-metals Metals conduct heat: particles are close enough together to pass on energy by conduction. Metals conduct electricity: Delocalised electrons Shiny: metallic lustre Malleable and ductile: The attractions between – and + are not broken, atoms simply rearranged Sonorous: make a sound when hit. High MP and BP: Attractions between – and + are strong. Some metals have other properties: Na floats on water, Hg is liquid at room temp, some are magnetic (Co, Fe and Ni)
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Chemical properties of metals They react with O 2 : metal oxides: basic oxides Metals above H in reactivity series react with water or steam Metal oxides/hydroxides (basic) are produced from this reaction. Metals react with acids to produce salt and H 2 gas. Semi metals : have some properties of metals, some of non-metals
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Noble gases – group 0 https://www.youtube.com/watch?v=qNaBMvJXdJ4
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The Noble Gases Colourless monatomic gases Radon is radioactive They get more dense as you go down the group The BP increases as there is a stronger attraction between larger atoms. More energy is needed to break these forces. They don`t form stable ions, no ionic compounds are formed. Too much energy is needed to rearrange the electrons to have an available electron to share in covalent compounds. Unreactive They can be made to react: Lighting: heating produces bright colours Argon in used light bulbs, it can get very hot and won’t react with the metal filament. Balloons: Helium very light and safer than H 2 (flammable!!!) Helium is mixed with O 2 in diving: makes mixture safer
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https://www.youtube.com/watch?v=m 55kgyApYrY
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Group 1- alkali metals Alkali metals: React with water to produce metal hydroxides, alkalis Low MP for metals and lower further down group Bigger atoms means that the nuclei are further away from the delocalized electrons and so get separated more easily. Low density for metals: Na, K and Li float on water. The density increases down group Soft : cut with knife. Shiny when cut, but tarnish in air quickly Stored in oil because there it reacts violently with air and water. Reactivity increases down group as larger atoms can lose their outer electron more easily as it is further from the positively charged nucleus.
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https://www.youtube.com/ watch?v=m55kgyApYrY Lithium: Lithium: http://www.periodicvideos.com/videos/00 3.htm Sodium: http://www.periodicvideos.com/videos/01 1.htm http://www.periodicvideos.com/videos/01 1.htm Potassium http://periodicvideos.com/videos/019.htm
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Reactions of group 1 Cold water + metal metal hydroxide + H 2 Burning in O 2 : they burn easily and produce coloured flames. Na (orange/yellow), Li (red), K (lilac). Other reactions with O 2 create a white solid, metal oxide. Group 7: they react easily and form a white solid. The new compound is ionic. Metal + acid salt + H 2 (this is often too dangerous as H 2 is flammable)
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Compounds Group 1 metal ions are colourless The compounds they form are colourless or white, unless negative ion is coloured (dichromate) They typically form ionic compounds that will dissolve in solution. Forming oxides is rare. Most of these metals react with H 2 O in the air to form hydroxides.
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Transition metals
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All have more than 1 e- in outer shell. Everyday metals are less reactive. They have either a slow or no reaction with water or air. Some react with acid, but not all. Which ones do? Above H in reactivity series Typical metals: what are the properties? High MP and BP (except Mercury) Often used as catalysts (Haber process (iron), catalytic converters (platinum), sulphuric acid (vanadium(V)oxide)) Variable vacancy : they can often form more than one type of ion, so different compounds are possible: example with Fe and Cu.
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Compounds Usually coloured Cu: blue or green Fe: green or brown
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Group 7 – the halogens https://www.youtube.com/watch?v=J7b2aBKa6-U
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Halogens, group 7 Halogen = salt maker All d iatomic MP + BP increase as you go down group as more attractions between larger molecules F 2 : Yellow gas, very reactive Cl 2 : Green gas Br 2 : Red liquid I 2 : Dark grey solid, purple vapour Have typical non-metal properties. All have poisonous vapours, one needs a fume cupboard when working with them chlorine video: http://www.periodicvideos.com/videos/017.htm
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Hydrogen halides Reacts to form hydrogen halides (HBr, HF): acidic, poisonous gases Forms covalent compounds, acidic when in solution (HCl) HCl in water: dissociates and conducts electricity HCl in methylbenzene: remains in molecular form and does not conduct electricity. https://www.youtube.com/watch?v=yW_C10cEzMk
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Metal halides Generally react to form metal halides These are REDOX reactions : metal is oxidized and non metal is reduced 2Na(s) + Cl 2 2NaCl(s)
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Halogen displacement reactions Reactivity decreases down the group: Size of atoms increases down the group, smaller non- metals can attract extra e- more easily. There is a greater attractive pull from the + nucleus in smaller atoms. Are all oxidising agents : more so higher up group. 2KBr (aq) + Cl 2(aq) 2KCl (aq) + Br 2(aq)
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Uses F 2 : toothpaste Cl 2 : swimming pools, water, in bleach Silver halides: in photography, light decomposes a compound and metallic Ag formed.
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