s - block Elements Flashcards
Why are alkaline earth metals called so ?
All alkaline earth metals (except called sodas their oxides and hydroxides are alkaline in nature and these metals oxides are found on the earth’s crust .
What is a diagonal relationship ? Why do they exist ?
The similarity between Li and Mg , Be and Al , and B and Si is called a diagonal relationship . This is due to the similarity in ionic sizes and charge/radius ratio of the elements .
What is the configuration of alkali metals ? Why are they never found in free state ?
The configuration of alkali metals is ns^1 . They readily lose electrons to give monovalent M+ ions . Hence , they are never found in free state in nature .
Write the order of hydration enthalpy of alkali metals .
Li>Na>K>Rb>Cs
What are the physical properties of alkali metals ?
All the alkali metals are silvery white , soft and light metals . Due to their large size , they have low densities . The melting and boiling points of the alkali metals are low indicating a weak metallic bond due to the presence of only one valence electron between them .
What happens when alkali metals come in contact with air ? What different oxides do they form ?
Alkali metals tarnish in dry air due to the formation of their oxides which in turn react with moisture to form hydroxides .
Lithium - monoxide
Sodium - peroxide
Potassium , Rubidium , Cesium - superoxide
Write the order of reactivity of alkali metals with water . How is Lithium different from the other elements in this case ?
Li
How do alkali metals react in liquid ammonia ?
The alkali metals dissolve in liquid ammonia to give deep blue solutions which are conducting in nature . The colour is due to the ammoniated electron which absorbs energy in the visible region of light thus imparting a blue colour to the solution . This solution is paramagnetic in nature .
In concentrated solutions , the blue colour changes to bronze colour and becomes diamagnetic .
Are alkali metals ionic or covalent ? What colours are the oxides of metals ?
Alkali metals are ionic in nature . The oxides and peroxide’s are colourless when pure , but superoxides are yellow or orange in colour . The superoxides are also paramagnetic .
Why does LiF and CsI have low solubility in water ?
The low solubility of LiF in water is due to it’s high lattice enthalpy whereas the low solubility of CsI is due to smaller hydration enthalpy of it two ions .
What is Sodium Carbonate ?
Sodium Carbonate (a.k.a Washing Soda) is NaCo3.10H2O . It is generally prepared through the Solvay process (see TB for full explanation) .
What are the properties of Sodium Carbonate ?
Sodium Carbonate is a white crystalline solid which exists as a decahydrate , Na2CO3.10H2O . On heating , the decahydrate loses it’s water of crystallisation to form monohydrate . Above 373K , the monohydrate becomes completely anhydrous and changes to a white powder called soda ash .
What are the uses of Washing soda ?
- It is used in water softening , laundering and cleaning .
- It is used in the manufacture of glass , borax and caustic soda .
- It is used in paper paints and textile industries .
- It is an important laboratory reagent both in qualitative and quantitative analysis .
