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Physical and Chemical Trends of Elements in Group 1 and Group 17 (GROUP 1,…
Physical and Chemical Trends of Elements in Group 1 and Group 17
GROUP 1
Rubdium
• Has a density of 1.53 g/cm3
• Lustrous metal
• Soft metal
• React with water violently
• 2Rb + H2O = 2RbOH + H2
• Melting point is 39.3C
• Boiling point is 688.0°C
POTASSIUM
• Lower density than water (0.89 g cm−3).
• Lustrous metal.
• Melting point is 63.5°C
• Boiling point is 759°C
2K + 2H2O = 2KOH + H2
CAESIUM
• Has a density of 1.873 g/cm3
• Soft metal
• Quickly reacted with air
• Melting point is 97.794°C
• Boiling point is 882.940°C
• Reacts explosively in water
• 2Cs + H2O = 2CsOH + H2
• Melting point is 28.5°C
• Boiling point is 671.0°C
SODIUM
• Lower density than water (0.97 g cm−3).
• Lustrous metal.
• Melting point is 97.794°C
• Boiling point is 882.940°C.
2Na + 2H2O = 2NaOH + H2
FRANCIUM
• Intensely radioactive metal
• Most of its physical properties are unknown
• Melting point is 21.0°C
• Boiling point is 650.0°C
• Theoretical reaction with water is causing an explosion
• 2Fr + H2O = 2FrOH + H2
LITHIUM
• lower density than water (0.534 g cm−3)
• lustrous metal
• Melting point is 180.50°C
• Boiling point is 1342°C
2Li + 2H2O = 2LiOH + H2
GROUP 17
IODINE
• Black solid, purple gas
• Many seaweeds contain iodine
• Needed in thyroid gland
• Nowadays added in table salt (for health purpose)
• Often used when people have cuts (antiseptic)
• Takes longer time to react with aluminium
• Really exothermic
• BP, MP and density higher than above elements
BROMINE
• Deep red
• Used in plastics
• Strong oxidizing agent
• Sharp smell and toxic
• Eg: react with aluminium to form aluminium triiodide
ASTATINE
• Dangerously radioactive element
• Short half-life of 8 hrs (compound decomposes easily)
• No uses discovered yet
CHLORINE
• Second most reactive
• Greenish yellow
• Poisonous, used as chemical weapon, cause build up of fluid in lungs
• Eg: react with water to form HCl
TENNESSINE
• Highly radioactive
• Only a few atoms ever been made
• Synthesised from nuclear fusion reaction
• Berkelium + Calcium-48 = Tennessine
• According to trends down the group, theorized to be black gas
• Short half-life
FLUORINE
• Most reactive (electronegativest) element, can react even with gold
• Pale yellow
• Eg: Reacts with platinum to form bright red gas
• Very low MP&BP
• Lowest density In group 17
General Trends
• Down the group, the melting point and boiling point increase.
This is because the intermolecular force (London forces) increases down the group
• The colour gets darker down the group
• Down the group, the reactivity decreases.
This is because down the group, the distance between nucleus to valence shell increases so harder to attract electron
General Trends
• The ions get larger as they go down the group
• The nucleus becomes further from the delocalised electrons and the attraction becomes weaker
• This means that less energy is required to break apart the lattice going down the group
• The reaction with water become more vigorous going down the group because the ionisation energy decreases as the size of the atom increases
• An alkali solution and hydrogen gas are formed when an alkaline metal reacts with water