The elements of Group 1 and Group 2 of the modern periodic table are called S-block elements. Two types of S-block elements are possible: the elements with one electron (s1) or the elements with two electrons (s2) in their s-subshell.

The S-block of the periodic table consists of 14 elements: Hydrogen (H), Lithium (Li), Helium (He), Sodium (Na), Beryllium (Be), Potassium (K), Magnesium (Mg), Rubidium (Rb), Calcium (Ca), Cesium (Cs), Strontium (Sr), Francium (Fr), Barium (Ba), and Radium (Ra).

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S Block Elements Guide

What are Block Elements?

Electronic Configuration of S-Block Elements

Properties of s-block Elements

Diagonal Relationships Within S-Block Elements

Frequently Asked Questions on S-Block Elements

S-Block Elements are elements in the periodic table that are located in the two columns on the far left of the table. These elements are characterized by having their outermost electron shell being an s-orbital.

The s-block elements with only one electron in their s-orbital are referred to as Group 1 or Alkali Metals, while those with two electrons filling their s-orbital are known as Group 2 or Alkaline Earth Metals.

The electrons present in an atom occupy various sub-orbitals of available energy levels in the order of increasing energy. The last electron of an atom may find itself in either of the s, p, d, and f subshells. Elements with their last valence electron present in the s-suborbital are referred to as s-block elements.

Electronic Configuration of S-Block Elements

The electronic configuration of S-block elements is outlined below:

The alkali elements in the s-block consist of a single valence electron in their outermost shell. This outermost electron is loosely held which makes these metals highly electropositive. Due to this, they are not available in the free state naturally. The general electronic configurations of s block elements - group 1 are as shown in the table below:

| --- |:---:| ---:|

| Lithium | Li | 1s22s1 |

| Sodium | Na | 1s²2s²2p⁶3s¹ |

| Potassium | K | 1s²2s²2p⁶3s²3p⁶4s¹ |

| Rubidium | Rb | 1s22s22p63s23p63d104s24p65s1 |

| Caesium | Cs | [Xe]\6s\1 |

| Francium | Fr | [Rn]7s¹ |

The following table displays the electronic configurations of elements included in group 2 of S block elements:

| Beryllium | Be | [He]2s2 |

| Magnesium | Mg | [Ne]3s2 |

| Calcium | Ca | [Ar]4s2 |

| Strontium | Sr | [Kr]5s2 |

| Barium | Ba | [Xe]6s² |

| Radium | Ra | [Rn]7s2 |

Properties of S-Block Elements

Both alkali and alkaline earth elements display a pattern of increasing properties as the atomic number increases within their respective groups. However, the first members of both the S block elements, Lithium and Beryllium, differ greatly from the rest of their members, but at the same time, they share more similarities with the element diagonally present in the next column.

The cause of the unusual properties of these S-block elements is;

1. Low atomic and ionic size

2. Higher Charge Density (Charge/Volume of the Atom)

3. Greater Polarization

4. Lack of d-orbitals.

The greater polarization of s block elements makes the first element more covalent and differentiates them from the rest which are ionic.

The similarity in size and charge density makes them exhibit a diagonal relationship with the element diagonally placed in the next group.

It is observed that the physical and chemical properties of the s block elements change in a particular trend as the atomic number of the elements increases. The changes in the various properties of the group are as mentioned below:

Chemical Properties of S-Block Elements

Atomic and Ionic Radii

When the s block elements of the modern periodic table are observed, it is seen that the size of the alkali metals is larger compared to other elements in a particular period. Additionally, as the atomic number increases, the total number of electrons increases along with the addition of shells.

The atomic number of the alkali metals increases as one moves down the group. This leads to an increase in both the atomic and ionic radii of the alkali metals.

![S Block Element Image 2]()

Ionization Enthalpy

The attraction between the nucleus and the electrons in the outermost shell decreases as we go down the group due to an increase in the size of the atoms. As a result, the ionization enthalpy decreases, with the alkali metals having a comparatively lower ionization enthalpy than other elements.

Hydration Enthalpy

As the ionic sizes of the elements increase, the hydration enthalpy decreases. Smaller the size of the ion, the higher the hydration enthalpy is, as the atom has the capacity to accommodate a larger number of water molecules around it due to the high charge/radius ratio and hence gets hydrated.

Physical Properties of S-Block Elements

In the S block elements, the density of the alkali metals decreases down the group, with the exception of potassium, which has a lower density than sodium.

The weak metallic bonding of alkali metals results in a low melting and boiling point.

The heat generated from the flame during a flame test excites the valence electrons of alkali metals and their respective salts, causing them to jump to a higher energy level and impart colour to the oxidizing flame. This helps to detect alkali metals.

Diagonal Relationship of S-Block Elements

![S Block Elements Image 3]()

A diagonal relationship exists between elements of the S block located in the second and third period of the periodic table. For example, Lithium (Group 1A, 2nd period) shows similarities with the properties of Magnesium (Group 2A, 3rd period).

The two elements beryllium and aluminium, located in the 2nd group and 2nd period, and 3rd group and 3rd period respectively, can be said to be diagonal pairs or diagonal neighbours as they show similarities in their properties.

The properties of S block elements vary significantly when compared to the other elements of the sub-group they belong to. However, their diagonal neighbours exhibit a lot of similarities. This relationship is evident as one moves left to right and down the group; the periodic table has opposing factors.

Therefore, when moving diagonally across the periodic table, the electronegativity of the S block elements remains almost unchanged due to the opposing tendencies of increasing across the period and decreasing down the group.

Similarities between Lithium and Magnesium

Lithium and magnesium have a higher hardness than the other elements in their respective groups.

Lithium and magnesium chlorides have the ability to be soluble in ethanol.

They are lighter than other elements in their groups.

The reaction of lithium and magnesium with water is gentle, and the oxides and hydroxides produced are less soluble.

In the presence of nitrogen, lithium and magnesium form their respective nitrides.

Superoxides are not formed when lithium and magnesium react with excess oxygen.

When magnesium and lithium carbonates are heated, carbon dioxide and its related oxides are formed.

Similarities between Beryllium and Aluminum

Aluminium hydroxide [link] and beryllium hydroxide react with excess alkali to form their respective ions.

Both these elements have the capacity to resist acid attack due to the presence of an oxide film on the surface of the metal.

Both of these metals have a tendency to form complexes.

The chlorides of both metals have the ability to dissolve in organic solvents.

#Frequently Asked Questions on S-Block Elements

Why does the first member of the s-block elements differ from the rest of their members considerably?

The anomaly of Lithium and Beryllium, the first members of the s-block family, is due to their difference from the rest of their members.

1. Low Atomic and Ionic Size

2. Higher Charge Density (Charge/Volume of the Atom)

3. Greater Polarization and

4. Lack of ’d’ orbitals.

⇒ Check: Preparation and Properties of Hydrogen Peroxide

The first element is more likely to form covalent compounds due to greater polarization, whereas the other elements form ionic compounds.

Is there a difference in properties between oxides of 1st group sodium and caesium and 2nd group magnesium and barium compounds? Give an example.

For example, the oxide of sodium (Na2O) is a white solid, while the oxide of magnesium (MgO) is a white powder. The oxide of caesium (Cs2O) is a yellow solid, while the oxide of barium (BaO) is a white powder.

Sodium and magnesium form oxides with oxidation numbers of -2 and -1, respectively, while heavier atoms form oxides with higher oxidation numbers. Sodium forms oxide and peroxide, where oxygen has an oxidation number of -2 and -1, respectively.

⇒ Also Check Out: Properties of d block elements

In magnesium oxide, oxygen is in a -2 state. But caesium forms super-oxides where the oxidation state of oxygen is – 0.5. Similarly, the heavier barium form peroxide having an oxidation state of oxygen as -1.

The difference between covalent and ionic compounds is that covalent compounds are composed of molecules, while ionic compounds are composed of ions. Covalent compounds can form hydrogen bonds with water molecules, allowing them to dissolve in water. Ionic compounds, on the other hand, are not able to form hydrogen bonds with water molecules, so they remain insoluble in water.

Solubility depends on two factors:

1. Formation of ionic entities through the breaking of bonds

2. The Energy of Solvation (Hydration Energy) of Entities through Ionic Interactions.

Check more:

Actinides

Lanthanides

F Block Elements

The enthalpy of dissociation of covalent compounds like beryllium sulphate is higher than that of ionic barium sulphate. However, due to the smaller size of beryllium and its higher charge density, the release of hydration enthalpy upon solvation is larger than the energy required for dissociation.

So, BeSO4 is more soluble than ionic BaSO4.

Which element is the strongest reducing agent in the preparation of S-block elements by electrolysis?

The S-block elements have a strong electropositive nature and low reduction potential, indicating their strong reducing ability compared to other elements. This means that substances with lower reducing ability than them will not be able to reduce them. The ability of an atom to reduce is related to the ease of releasing electrons for reduction. Since the ionization energy decreases down the column, this suggests that Caesium is a stronger reducing agent than Lithium.

But, reducing ability (oxidation potential) depends on the combined energy difference of three processes:

Sublimation of the Atom

The metal ion undergoes ionization

Hydration of the ion with water.

Lithium, being the smallest ion, has a higher hydration enthalpy than caesium, and its higher ionization enthalpy is more than compensated for. This makes lithium have the highest reducing ability (highest oxidation potential or lowest reduction potential = -3.04V) compared to caesium.

Yes, there is an easy way to identify the presence of the S block element.

The block elements or their halides, when exposed to flame, undergo electronic transitions in the visible region of the light spectrum, resulting in the induction of characteristic colours into the flame. These colours are:

| Flame Colour | Crimson Red | Yellow | Violet | Red Violet | Blue |

| Metals | Beryllium | Magnesium | Calcium | Strontium | Barium |

|:———|:———–:|:————:|:———-:|:————:|:———:| | Metals | Beryllium | Magnesium | Calcium | Strontium | Barium |

| Flame Colour | Brick Red | Crimson Red | Apple Green |

S-Block Elements: Important Topics

![S-Block Elements - Important Topics]()

S-Block Elements: Important Questions

![S-Block Elements - Important Questions]().

S-Block and P-Block Elements

D-Block and F-Block Elements