4: Inorganic + The Periodic Table Flashcards
Lithium (Li+) flame color
Scarlet red
Sodium (Na+) flame color
Bright yellow
Potassium (K+) flame color
Lilac
Rubidium (Rb+) flame color
Red
Caesium (Cs+) flame color
Blue-violet
Magnesium (Mg+2) flame color
No visible flame
Calcium (Ca+2) flame color
Brick-red
Strontium (Sr+2) flame color
Red
Barium (Ba+2) flame color
Apple-green
What is the trend in ionization energy down group 2?
Ionization energy decreases
What is the reason for the trend in ionization energy down group 2?
(Decreases) because:
- Electrons are held further from the nucleus, lower attraction
- More shielding, lower attraction
- Electrons are therefore easier to remove
What is the trend in reactivity down group 2?
Reactivity increases down group 2
What is the reason for the trend in reactivity down group 2?
(Increases) because:
- Electrons are held further from the nucleus, lower attraction
- More shielding, lower attraction
- Electrons require less energy to remove
Group 2 metal + Oxygen ?
Burn readily in oxygen, forming XO compounds
What precautions are needed and why when using Mg ribbon?
MgO forms slowly when Mg metal is exposed to oxygen, so the ribbon needs to be cleaned off to remove MgO which reacts differently to pure Mg
Group 2 metal + Chlorine?
Form the compound XCl2
Mg + steam ?
Forms MgO and hydrogen gas
Mg + warm water ?
Forms Mg(OH)2 and hydrogen gas
Ca, Sr, Ba + cold water ?
Form hydroxides and hydrogen gas
What would be observed when a group 2 metal reacts with water?
- Effervescence
- Metal dissolves
- Solution heats up
- Solution turns alkaline
Group 2 oxide + water?
Form hydroxides, increasing in pH as you go down the group
What is the trend in group 2 hydroxides ?
Increase in pH going down the group because more OH- ions are free in solution
Group 2 hydroxide + (dilute) acid?
Form a salt and water
Group 2 hydroxide + acid?
Form a salt and 2 water molecules
What is the trend in solubility of group 2 hydroxides?
Become more soluble down the group
- Mg classed as insoluble
- Ca reasonably soluble
- Ba very soluble
What is the trend in solubility of group 2 sulfates?
Become less soluble down the group
- BaSO4 is the least soluble
Group 2 oxide + acid?
Form hydroxides and water
Group 2 hydroxide + acid?
Form hydroxides and 2 water molecules
What is the trend in solubility of group 2 hydroxides?
Solubility increases down the group
What is the trend in solubility of group 2 sulfates?
Solubility decreases down the group
What is thermal decomposition?
The use of heat to break down a reactant into more than one product
What is thermal stability?
The ease of which a compound thermally decomposes. If a compound has high thermal stability, it will not decompose as easily
What is the trend in thermal stability of group 1 + 2 carbonates?
Thermal stability increases going down the group
What is the reason for the trend in thermal stability of carbonates?
Cations with a smaller charge/density ratio have less polarizing power and do not distort the carbonate ion’s bonding electrons as easily. The C-O bond is less weakened and needs more heat energy to be broken
Do group 1 or group 2 carbonates thermally decompose more easily?
Group 2 carbonates are less thermally stable overall because they have larger charge-density ratios than their corresponding group 1 carbonate
How do you investigate thermal decomposition of carbonates?
It gives off CO2 gas, so by using lime water and timing how long it takes for it to become permanently cloudy, thermal stability can be compared
What is the trend in thermal stability of group 2 nitrates?
Thermal stability increases down the group
What is the reason for the trend in thermal stability of group 2 nitrates?
Cations with a smaller charge/density ratio have less polarizing power and do not distort the nitrate ion’s bonding electrons as easily. The N-O bond is less weakened and needs more heat energy to be broken
How do you investigate the thermal decomposition of nitrates?
- Brown gas will evolve
- Nitrate solid melts into a colorless solution, then re-solidifies
What is the reason behind flame colors?
Electrons are excited by the heat energy and move to a higher energy level. Upon their return to their original energy level, energy is released, which is seen as light energy (the flame color)
How do you investigate flame colors?
Clean a nichrome wire with hydrochloric acid and dip into the solution of cations. Hold over the Bunsen flame and observe the color of the flame
