The Periodic Table Chapter 12

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.

Metals and Non-Metals

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)

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

Noble gases – group 0

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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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.

watch?v=m55kgyApYrY  Lithium: Lithium: 3.htm  Sodium: 1.htm 1.htm  Potassium 

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)

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.

Transition metals

 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.

Compounds  Usually coloured  Cu: blue or green  Fe: green or brown

Group 7 – the halogens

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:

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.

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)

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)

Uses  F 2 : toothpaste  Cl 2 : swimming pools, water, in bleach  Silver halides: in photography, light decomposes a compound and metallic Ag formed.