Periodicity Flashcards
periodicity
a repeating trend in physical and chemical properties of the elements across each period of the periodic table
similar chemical properties because
similar electron configuration
ptable arranged in order of
atomic number Z
blocks correspond to
highest energy subtle (s then d then p then f below)
first ionisation energy
the energy required to remove 1 electron from each atom in 1 mol of gaseous atoms of an element to form 1 mol of gaseous 1+ ions
electron shielding
electrons are negatively charged, inner shell repel outer shell electrons. This shielding reduces attraction between nucleus and outer electrons.
second IE
the energy required to remove 1 electron from each atom atom in 1 mol of gaseous 1 + ions of an element to form 1 mol of gaseous 2+ ions
IE gives you information on
the number of outer electrons, the group, the identity of the element
How to answer IE questions
….increases nuclear attraction, more IE needed to remove outer electron.
giant metallic lattice
a three dimensional structure of positive ions and delocalised electrons, bonded together by strong metallic bonds
are metals soluble?
no, any interaction would lead to reactions rather than dissolving
giant covalent lattice
a three dimensional structure of atoms bonded together by strong covalent bonds
giant covalent lattice solubility
insoluble in almost all solvents, covalent bonds way to strong to be broken by solvent interaction
which giant covalent lattice can conduct electricity
graphene and graphite
which giant covalent lattice can’t conduct
diamond (a form of carbon), silicon
how to answer redox questions
loss or gain, reduction/oxidation , change in oxidation number
solubility of group 2 hydroxides trend
more soluble going down group, more OH- ions released, more alkali solution
reactivity of group 2 metals trend
most energy input from first 2 IE, greater electron shielding and radius so easier to remove electrons, reactivity inc going down, less IE needed, stronger reducing agents
how soluble are group 2 oxides
slightly soluble, precipitate forms in saturated solution
why are group 2 useful
basic properties, ability to neutralise acids
group 2 metal uses
agriculture: farmers add calcium hydroxide as white lime to neutralise acidic soils- forms calcium ions and water
antacids: for indigestion calcium carbonate (forming calcium chloride, CO2, H20) and milk of magnesia, MgOH2, slightly soluble, suspension in water (forming MgCl2 and water)
how are halogens found
as stable halide ions as solid deposits in salt mines with sodium/potassium or dissolved in sea water, most reactive non-metals
structure of halides
simple molecular lattices
halogen boiling points
going down group, molecule size increases, electrons increase, london forces increase, more energy needed to break INC STRONGER forces, higher bp
oxidising agent trend
reduces strength as descend down group
in halogen halide reactions
if halogen more reactive, acts as an oxidising agent , and displaces halide in redox reaction
in water, colours of halogen
yellow, orange, brown for chlorine, bromine, iodine
why is cyclohexane used in halogen halide reactions
to make distinction between bromine and iodine, makes them orange and violet. the organic non-polar solvent dissolves easily with the non-polar halogen solutions
what determines the colour of a halide halogen reaction solution
the halogen NOT the halide and its the top layer
colours of halogens
fluorine- pale yellow gas, chlorine- pale green gas, bromine- red/brown liquid, iodine- shiny grey/black solid
disproportionation
when, in the same redox reaction, the same element is reduced and oxidised simultaneously e.g. chlorine and water to make HCl and HClO
chlorine uses
water disinfectant, protects against waterborne diseases
HClO (chloric 1 acid) and ClO- ions
kill bacteria, and HClO acts as a bleach so UI goes red bc acid then colour fades bc bleach
Cl water solubility
low water solubility so dissolve in cold aqueous NaOH, forms NaClO and H20 and NaCl. ClO- ions, used as household bleach
