S Block Flashcards
What groups are in the s block?
1 and 2
What are the main characteristics of s block elements?
Metallic character
Low electronegativity
Basic oxides, hydroxides
Ionic bond with fixed oxidation states
Characteristic flame colours
Weak tendency to form complexes
Explain the metallic character.
High tendency to lose electrons to form positive ions.
Metallic character increases down both groups.
Explain electronegativity.
Low nuclear attraction for outer electrons.
High electropositive.
What s block elements form basic oxides?
All
What s block elements form peroxides?
Na, K, Rb, Cs, Ba
What s block elements form super oxides?
K, Rb, Cs, Ba
What are the trends in group 1 hydroxides?
All are soluble, base strength increases down group.
What are the trends in group 2 hydroxides?
Solubility increases, amphoteric to basic, base strength increases down group.
What are the flame colours of the group one elements?
Li = deep red
Na = yellow
K = lilac
Rb = bluish red
Cs = blue
What are the flame colours of the group two elements?
Ca = brick red
Sr = blood red
Ba = apple green
Why do s block elements have a weak tendency to form complexes?
No low energy vacant orbitals available for bonding with lone pairs of surrounding ligands
How does atomic radii change?
Increases down the group
How does ionisation energy change?
Decreases down the group
Explain ionisation enthalpies of group 1 elements.
Low first IE as well shielded from nucleus by inner shells.
Removal of second electron harder due to it being in the inner shell.
As atomic radius increases the outer electron is further away from the well shielded nucleus.
Explain ionisation enthalpies in group 2.
Low first and second IE.
Removal of the third electron harder as from inner shell.
IE of group 2 generally higher than group 1.
Describe the trends of hydration enthalpy in the s block.
Decreases down group, as ions get bigger, charge density decreases, electrostatic attraction between ions and water molecules gets smaller.
Group 2 > 1, doubly charged and smaller.
How does melting point change in the s block elements?
Decreases down the group, exception of sharp drop of Mg below Ca.
Explain s block reactions with oxygen.
Strong reducing agents, reducing power increases down both groups. React readily with O.
Be and Mg to be stored under paraffin.
What s block elements react with hydrogen?
All bar Be.
What are the uses of sodium carbonate?
Manufacture of glass
Water softening
Paper industry
What are the uses of sodium hydrocarbonate?
Baking powder
Soft drink
What are the uses of sodium hydroxide?
Soaps, dyes, paper, drugs
Rayon
What are the uses of magnesium hydroxide?
Milk of magnesium
What are the uses of calcium hydroxide?
Neutralize acids in waste water treatment..
