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Group 1 of Periodic Table: Alkali Metal (Trends going down the group…
Group 1 of Periodic Table: Alkali Metal
Potassium, K
Physical Appearance and Properties
density : 0.862 grams per cubic centimeter
melting point : 63°C (145°F)
boiling point : 770°C (1,420°F).
metallic and silvery white
so active that it never occurs free in nature
Chemical Reaction & Properties
reacts with water violently and gives off hydrogen gas:
2 K (s) + 2 H2O (l) → 2 KOH (aq) + H2 (g)
reacts readily with all acids and with all non-metals, such as sulfur, chlorine, fluorine, phosphorus, and nitrogen
Caesium, Cs
Chemical Reaction and Properties
Reaction of caesium with air
Cs(s) + O2(g) → CsO2(s)
Reaction of caesium with water
2Cs(s) + 2H2O → 2CsOH(aq) + H2(g)
Reaction of caesium with halogens.
2Cs(s) + F2(g) → CsF(s)
Physical Appearance and Properties
Silvery white, almost pale gold
Melting point: 28.5°C, solid at room temperature
First ionisation energy: 375.7 kJ mol‑1
Boiling point: 671 °C
Trends going down the group
Melting and Boiling points
Decreases down the group
Strength of metallic bond decrease
As the atoms increase in size, the distance between the nuclei and these delocalized electrons increases; therefore, attractions fall.
Atoms are more easily pulled apart
Density
Increase down the group
Reactivity
Increase down the group
The outer electron become further apart from the nucleus
Less attraction between nucleus and valence electron
Easier to remove valence electrons
Atomic Radius
Increase down the group
Because increasing number of electron shells
First Ionisation Energy
Decrease down the group
Because of increasing distance between nucleus and outermost electron
Electronegativity
Decrease down the group
Because of increasing size of atom
Therefor the force of attraction of nucleus to electron from other atoms decreases
Lithium, Li
Chemical Reaction
reacts with water to form lithium hydroxide and hydrogen gas
2
Li
+ 2[H2O] → 2
LiOH
+
H2
+ energy
Chemical Properties
floats on water
highly reactive
form strong hydroxide solution
Physical Appearance and Properties
density : 0.53 g.cm -3
melting point : 180.5 °C
boiling point : 1342 °C
Sodium, Na
Chemical Reaction & Properties
Na + H2O →NaOH + H2
reacts with water to form sodium hydroxide and hydrogen
Physical Appearance and Properties
melting point : 97.82°C
boiling point : 881.4°C
density ; 968 kg/m³
Francium, Fr
Chemical Reaction and Properties
Highly radioactive
Least electronegative element of all
Physical Appearance and Properties
Unknown physical properties and appearance.
Liquid in room temperature.
Presumed to be silver-grey-metallic metal
Density of solid: 2900 (estimated) kg m-3
Boiling point: 598 °C
Rubidium, Rb
Physical Appearance and Properties
Rubidium is a soft, silvery-white metallic element
Melting point 39.30°C, solid at room temperature
Boiling point: 688 °C
Density: 1532 kg m-3
Chemical Reaction and Properties
Rubidium reacts with water to form colourless solution of rubidium hydroxide (RbOH) and hydrogen gas (H2).
2Rb+2H2O→ 2RbOH+H2
Reaction of Rubidium with air
Rb(s) + O2(g) → RbO2(s)
Forms dark brown rubidium superoxide, RbO2
Reaction of Rubidium with halogens
2Rb(s) + F2(g) → RbF(s)