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Group IA Alkali Metals & Their Compounds - Coggle Diagram
Group IA Alkali Metals & Their Compounds
electron structure
one electron in outer shell
found in group 1
similar physical and chemical properties
readily lose the outer shell electron to form positive ions with a +1 charge
trend in density
down the group, more dense but the trend is not perfect because K is less dense than Na.
properties
physical properties
• Soft metals with silvery colour.
• Good thermal/electrical conductors
• Li -> K - less dense than water,
• Rb&Cs –more dense
• Kept in oil in order to avoid oxidation
• Melting points decreases down the group
• Ionic/atomic radii increases down the group
• Density increases down the group
• Ionization energy,IE decreases down the group
• Electron affinity, EA decreases down the group (magnitude)
•Adhering properties increased down the group
general
Each atom in this group consist of one valence
electron in the s orbital
reactivity of metal
down a group
Increase in size
Increase in shielding effect
Decrease in Ionization Energy (IE) - Low ionization energy
exist as ionic compunds
eg: NaCl
compounds
crystal structure: Body Centered Cubic (BCC)
exist as covalent compounds
eg: Na2
soluble in water
normally white in colour except KMnO4-purple
very high melting points
Lattice energy of the salt
The separation of free ions in gas phaseneed energy so /_\Hlatt (+ve)
M+X-(s) -> M+(g) + X-(g)
Hydration energy
towards free ions involves released energy -> Esolv./hyd (-ve)
M+(g) + X-(g) -> M+(aq) + X-(aq)
the smaller the size of the ions, the bigger the ionic charge -> the stronger the bond between ions and solvent. So, more energy is released.
colour of flame
Li- crimson
Na- yellow
K- red- lilac/violet
Rb- red
Cs- blue
metal is extremely reactive
Very Electropositive, forming positive ions
(Cations) -> act as Electron Donor
chemical
wet air
(O2, H2O, CO2)
Slow to form oxide -> hydroxide -> carbonate
4M + O2 -> 2M2O (M= Na, K)
M2O + H2O -> 2MOH
2MOH + CO2 + nH2O -> M2CO3.nH2O
H20
Very reactive H2 evolve, base solution
M+2H2O->2MOH+ H2 (M=Li < Na < K < Rb <.Cs)
increasing alkalinity
solubility
Hydration energy
the smaller the size of the ions, the bigger the ionic charge -> the stronger the bond between ions and solvent. So, more energy is released.
ion size: Li+ < Na+ < K+ < Rb+ < Cs
towards free ions involves released energy -> Esolv./hyd (-ve)
M+(g) + X-(g) -> M+(aq) + X-(aq)
Lattice energy of the salt
The separation of free ions in gas phase
need energy so /_\Hlatt (+ve)
M+X-(s) -> M+(g) + X-(g)
existence
Li
Petalite
Ambligonite
Spodumene
Na
Rock salt
Sea water
Chile saltpeter in Chile
Soda lakes
Borax, at Nevada USA
Cryolite
K
Silvin
Carnalite
Kainite
Leonite
extraction
K, Rb and Cs Metals
K cannot be obtained by electrolysis of the KCl due to
the melting point of KCl (776 °C) is higher than K metal (762 °C)
K metal dissolves in molten salt
Discharge potential for K+ and Ca2+ is similar, if the molten used KCl-CaCl2
Reduction of molten chloride with Na vapour
MCl(l) + Na(g) M(l) + NaCl(l) e.g. Potassium
KCl(l) + Na(g) NaCl(s) + K(l)
application
Lithium
LiAlH4 - reducing agents for organic compounds – produce H.
Lithium complex oxide, LiNbO3 – use in mobile communication devices – due to nonlinear optical and acousto-optical effect
sodium
as coolant in reactor nuclear
NaCl – flavouring food, road de-icing
Potassium
Cs – alloy with Al and Ba is used in photoelectric cell
compounds of alkali metals
hydrides
preparation
Directly from metal and H2 gas->form saline hydride
Reaction between group IA oxides in a flow of H2 gas
M2O(s) + H2(g) -> MH(s) + MOH(s)
physical properties
ionic crystal
colourless
m/p: LiH=700oC, NaH/KH~400oC
reactions
React violently with water
Reaction with alcohol -> alcoholate
Reaction with liquid ammonia -> amide
Reaction with oxygen -> oxide
uses
As reducing agent : produce H2
as source of hydrogen gas
as fuel
oxides
monoxide (M2O)
peroxide (M2O2)
uses
as bleaching agent
superoxide (MO2)
to get rid of CO2 and produce O2 in a closed area
carbonates (M2CO3)
Solvay process
Na2CO3
properties
Colourless and transparent solid
Exist as hydrated salt
application
A precursor for GLASS manufacturing industries
In manufacture of sodium silicate/water glass
Manufacturing of soap and detergent
As hard water softener
Manufacturing of borax
K2CO3
MHCO3
Application
NaHCO3
baking powder
fire extinguisher
KHCO3
gastric medicine
buffer in wine product & water treatment
buffer in low pH liquid detergent
nitrate
NaNO3
• Deliquescent solid
• Used in making other nitrates, fertilizers and explosives
KNO3
Naturally occurs as mineral saltpetre
Slightly soluble in cold water but very soluble in hot water
Used in manufacturing explosives, fireworks, matches and fertilizers
hydroxide
NaOH & KOH:
Industrial Process
electrolysis
Electrolyte: Brine (Concentrated NaCl)
Anode: Carbon (Graphite),
Cathode : Mercury
uses
soap industry
bleaching agent
halides (MX)
Trend of /
\Hf
• F- to I- : /
\ Hf becomes less negative due to increase radius of the anion and , /_\Hlatt becomes less negative
down the group,
/_\Hf for Cl-, Br-, I- becomes
more negative
/
\Hf for F- becomes less negative due to increase in radius of M+ , /
\Hlatt also
decrease (less negative)
Thermal & Solubility of Salt of Group IA
stable- high electro+ve charge
Li2CO3 – decompose upon heating
Li2CO3->Li2O + CO2
Other carbonate : do not decompose
Anomaly of Lithium from other alkali metals
Exhibit covalent character in its bonding
Form normal oxide, Li2O
LiH is stable to heating to 900oC, Other hydride decompose above 400oC
Diagonal Relationship (Li-Mg)
due to similar in atomic size and electronegativity,
Only form low oxide (normal) when heated in oxygen/air
carbonates easily decomposed to CO2 and an oxide when heated.
sulphates and carbonates salts insoluble in water
Formed carbides and nitrides on direct heating in C and N2
Halides soluble in various organic solvents
nitrates decomposed to an oxide, nitrogen dioxide and oxygen
when heated