Class 11 Chemistry Chapter 10 NCERT Solutions
NCERT Solutions Class 11 Chemistry Chapter 10 PDF
The elements in the modern periodic table have been divided into s-block, p-block, d-block and f-block based on the presence of valence electrons in its orbitals. The electrons of the s-block elements enter the s-orbital, which has the capability of holding only 1 or 2 electrons in its outermost orbital. Group 1 and Group 2 elements of the modern periodic table are grouped into the s-block elements. The Group 1 elements comprise of all the alkali metals and the Group 2 elements comprise of all the alkaline earth metals.
What are S block elements?
The group 1 and 2 elements of the periodic table are called s block elements. These elements have valence electrons in their s subshell. The following elements are present in s block:
Hydrogen , Helium, Lithium, Sodium, Beryllium, Potassium, Magnesium, Rubidium, Calcium, Caesium, Strontium, Francium, Barium and radium.
Alkali and alkaline earth metals:
- The elements that have one electron in their subshell are called alkali metals.
- The elements that have two electrons in their subshell are called alkaline earth metals.
The general electronic configuration of s-block elements
For alkali metals is [noble gas]ns1
Example of alkali metals:
Li: 1s2 2s1
Na: 1s2 2s2 2p6 3s1
For alkaline earth metals it is [noble gas] ns2 .
Example for alkaline earth metals:
Be: [He] 2s2
Mg: [Ne] 3s2
General properties of S block elements:
- Small atomic and ionic size
- High polarisation
- Low melting and boiling point
- Absence of d orbitals
Trends of S block elements in periodic table:
Down the group:
- Atomic and ionic radii of the metal increases as the atomic size increases
- Ionisation enthalpy decreases as the atomic size increases
- Hydration enthalpy increases as the ionic size increases
Across the period:
- Ionization energy increases
- Electron affinity and electronegativity increases.
Diagonal relationship in S block elements:
- Some of the elements show similar properties diagonally adjacent in the second and third periods of the periodic table is called diagonal relationship. For example, Lithium of group 1A and second period shows similarities with the properties of magnesium which are located in the 2nd group and 3rd period.
Lithium and Magnesium have similar properties:
- Lithium and magnesium react gently with water. The oxides and hydroxides are less soluble.
- In the presence of nitrogen, lithium and magnesium form their respective nitrides in presence of nitrogen
- When lithium and magnesium react with excess oxygen, Carbon dioxide and their respective oxides are formed when carbonates of magnesium and lithium are heated carbon dioxide and respective oxides are formed.
Beryllium and Aluminum have similar properties:
- They form complexes.
- Chlorides of these metals are soluble in organic solvents.
- Aluminum hydroxide and beryllium hydroxide react with excess alkali to form their respective ions.
For more information on NCERT Solutions for class 11 chemistry, Chapter 10 S Block Elements, check the solutions given below.