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IB Periodicity
Question | Answer |
---|---|
Atomic radius | increases going down a group because of adding energy levels; decreases going left to right across a period because of adding protons while keeping electrons in same principle energy level. |
Ionic radius | cation radius is smaller than atomic radius because they contain fewer electrons than protons; anion radius is larger than atomic radius because they contain more electrons than protons. |
cation | positive ion |
anion | negative ion |
melting points | depend on both structure of the element and type of intermolecular forces |
electronegativity | relative measure of the attraction that an atom has for a shared pair of electrons when it is covalently bonded to another atom. As size of atom decreases, electronegativity increases. |
alkali metal properties | reactive, good reducing agents. Reactivity increases down the group as the outer electron is in successively higher energy levels and less energy is needed to remove it. |
halogens | good oxidizing agents, reactivity decreases going down the group as the outer shell is increasingly at higher energy levels and further from the nucleus, decreasing the attraction for another electron. |
reactions between halogens | Cl is a stronger oxidizing agent than Br so it can remove the electron from Br ions in solution to form Cl ions and Br2. Both Cl and Br can oxidize I ions to form Iodine. |
test for halide ions | the presence of halide ions in solution can be detected by adding silver nitrate solution. the silver ions react w/ the halide ions to form a precipitate of silver halide that can then be distinguished by their color. AgCl-white; AgBr-cream; AgI-yellow |
metal oxides | basic. high melting pt with period 3 metals. conduct electricity when molten |
non-metal oxides | acidic. low melting pt with period 3 non-metals |
aluminum oxide | amphoteric, can act as a base or an acid |
silicon dioxide | weak acid, does not react w/ water |
period 3 metal chlorides | conduct electricity when molten. high melting pt. neutral or weakly acidic |
period 3 non-metal chlorides | don't conduct electricity in molten state. low melting pt. acidic |
transition element | an element that possesses an incomplete d sub-level in one or more of its oxidation states. Lose 4s electrons first, then 3d electrons. |
ligands | neutral molecules or anions which contain a non-bonding pair of electrons that can form co-ordinate covalent bonds with the metal ion to form complex ions. ex. water |
co-ordination number | the number of lone pairs bonded to the metal ion. |
transition metal catalysts | because they can exist in a variety of oxidation states, transition metals make good catalysts. Fe in Haber process; Vanadium oxide in Contact process |