Chemical Reactivity Flashcards
- why do metals have high melting points?
- the free electrons in metal doesn’t get attached w/ other atoms in metal. why?
- have strong intermolecular forces b/w atoms. Electrostatic attraction forces b/w metal ions (metals tend to lose electrons so + charge) & free electrons (- charge) create strong metallic bonds.
- cz metals lose e- not gain
the tendency to form cation _______ left to right?
electropositivity ______ along a group.
define oxide?
w/ reasons
decreases
increases
a compound composed of oxygen & another element, typically forming when elements react with oxygen.
what is electropositive character? state reaction
the basic character of metal oxides _______ down a group. what does this inidcate?
The tendency of an element to lose electrons to form cations is called the electropositive character of an element.
M(s) → M+n (g) + ne-
increases
increase in metallic/electropositive character
as metal oxides are basic
aka metallic character
why in a group the reactivity of metals with oxygen increases?
The acidic behaviour of acid is due to _____________________.
The basic behaviour of base is due to _____________________.
due to the decrease in ionization energy (the increase in the ease of losing valence electrons). large atomic size
presence of hydrogen ions, H+ ions.
presence of hydroxyl ions, OH- ions.
________ are basic & acidic in charcater.why?
reactivty of metals with O ____ across a period. why?
most common alkali & alkali earth metals?
metal oxides
non metallic oxides
decreases
Na
Mg & Ca
why are alkali metals never found in free state? then how are they deal with?
why is Na soft?
they are highly reactive cz of low ionization energy.
placing in kerosene oil
large size & 1 electron weak metallic bonds
to prevent it from coming in contact with oxygen and moisture. If this happens, it will react with the moisture present in air and form sodium hydroxide which is a highly exothermic reaction.
why are alkaline earth metals less reactive than alkali metals?
It takes more energy to remove 2 valence electrons from an atom than 1 valence electron.
in short ionization energy of alkali metals is less.
milk of magnesia? use?
Mg(OH)2 Magnesium hydroxide
basic
used as antacid & to relieve constipation
preventing acidity
what are noble metals?
do these metals react? with whom & how?
some metals are difficult to oxidze they are Ag, Au, Cu, Pt
Cu & Ag exist in both free & combined states. by reacting with strong oxidizing agents
Au & Pt exist mostly in free state
they only react with Aqua Regia which is a mixture of 3 parts of conc. HCl with 1 part of conc HNO3
1 part of HNO3 to 3 parts of HCl by volume.
Au= gold
importance of sliver & gold?
- gold alloys are extensively used in dentistry
- some compounds of gold have useful therapeutic applications. eg salts of gold are used to treat rheumatoid arthritis.
- silver is an excellent conductor of heat & electricity it is used to make utensils.
- due to high malleability of silver it is used to make jewellery.
- light sensitive silver halides are used in photographic processes
importance of Pt?
what are non-metals? nature? metalloids? examples?uses?
elements that poorly conduct electricity & heat
generally gases or brittle soilds at room temp. except Br which is liquid.
elements that have mixed properties of metals & non-metals. Some of these play important role in modern electronic materials.
Example Silicon & Germanium are metalloids that are used in the manufacture of computer chips & solar cells.
electronegative character? ______ group
________ across a period? how?
The tendency of an element to gain electrons to form negative ions is called the electronegative character of an element.
decreases due to increase in atomic size
increases due to increase in nuclear charge & decrease in atomic size
name all properties of halogens? (physical & chemical)
what is the most & least reactive halogen?
- reactive
- non-metals
- exist as diatomic molecules.
- react w/ metals to form salts called halides. (halides - oxidizing agent ofcourse)
- reacts with hydrogen to form hydrogen halides. H2 (g) + X2 (g) → 2HX (g)
- hydrogen halides dissolve in water to form hydrohalic acid eg HCl, HF, HI, HBr.
F2 & I2
metals + halogen = halide
H + halogen = hydrogen halide
increasing acidic strength of hydrogen halides?
decreasing oxidising power of halogens?
reactivity of halogens _________ along a group. why?
HF < HCl < HBr < HI
F > Cl > Br > I
decrease
as you go from HF to HI, the acidic strength increases because the bond b/w hydrogen & halogen becomes weaker, making it easier for hydrogen to dissociate as a proton in solution.
decreasing = big to small
atomic radius increases with an increase of shells. This lessens the attraction for valence electrons of other atoms, decreasing reactivity. This happens for all other elements.
