S Block Elements (original) (raw)

Last Updated : 23 Jul, 2025

S-block elements are those elements in which the last electron is present in the s-orbital. In the periodic table. They reside in the first 2 columns. S-block consists of 14 elements that include, Hydrogen (H), Lithium (Li), Helium (He), Sodium (Na), Beryllium (Be), Potassium (K), Magnesium (Mg), Rubidium (Rb), Calcium (Ca), Caesium (Cs), Strontium (Sr), Francium (Fr), Barium (Ba), and Radium (Ra).

In this article, we will learn about s-block elements, their various properties, and others in detail.

Table of Content

• What are s-block Elements?
• Properties of s-block Elements
• Atomic Mass of s-block Elements
• Diagonal Relationship of s-Block Elements
• Periodic Trends in s-Block Elements
• Compounds of s-block Elements

What are s-block Elements?

You all are well-familiar with the concept of the modern periodic table. In the modern periodic table, we learn about 4 kinds of blocks i.e. s-block, p-block, d-block & f-block. Here, we will learn the definition of s-block elements. It is the most intriguing block of the periodic table.

The element which enters in the outermost s-orbital are known as s-block elements.

S-block elements consists 2 groups i.e. Group 1 & Group 2. Group 1 consists elements which are called as alkali metals while Group 2 consists metals which are called as alkaline earth metals.

• Group 1- Alkali Metals
• Group 2- Alkaline Earth Metals

What are Alkali Metals of Group 1?

Have you ever wondered why sodium causes a fizzy explosion when it is dropped in water? We will uncover this further.

• Group 1 elements are called alkali metals because they make hydroxides, whenever reacts with water. You all know that water is strongly alkaline. Here you got your answer for the above question.
• Alkali metals are well-known for their extreme reactions & their easy bond with other elements. The elements of Group 1 have 1 valence electron in their outermost s-orbital.

**Learn more about, **Alkali Metals

What are Alkaline Earth Metals of Group 2?

• During any occasion, you buy fireworks right? And when you light them up, they starts glowing & gives a beautiful view. It's the magic of none other than our magnesium.
• Group 2 introduces us the alkaline earth metals which exists in the earth's crust. The interesting thing here is that their oxides & hydroxides are alkaline in nature. The elements of Group 2 have 2 valence electrons in their outermost s-orbital.

**Learn more about, **Alkaline Earth Metals

Table of S-block Elements & Their Symbol

S-block comprises total 14 elements which are classifies into 2 groups: Group 1 & Group 2. The classification of these 14 elements are given below in tabular form:

Electronic Configuration of S-block elements

Electronic Configuration of s-block elements is added in the image below,

Difference between Group 1A and Group 2A Elements

Let's learn the basic differences between the elements of Group 1 & Group 2 on the basis of some characteristics:

Properties of s-block Elements

The S-block elements possesses distinct properties. In this section, you'll learn about the properties of s-block elements. Their properties mainly categorized into 2 parts:

• Physical Properties
• Chemical Properties

Physical Properties of s-block Elements

Let's dive deep into the properties of s-block elements

• **Melting Point: S-block elements consists different melting points. The Group 1 elements i.e. Alkali metals have low melting point. For example, Sodium can be melted around 98° celsius. When we talk about Group 2 elements i.e. Alkaline Earth Metals, they have high melting point. For example, Calcium needs 842° celsius temperature to melt which is 9 times more than sodium needs.
• **Conductivity: Due to the presence of electrons that are loosely bound, these electrons can easily move through the metallic structure. This encourages the flow of electricity. That's why s-block elements have higher electrical conductivity.
• **Nature of Bonds: In S-block, the Group 1 elements i.e. Alkali metals always form ionic bonds as these elements have low ionization enthalpies that decreases downwards to the group. In simple words, as we move down the group, the ionic characteristic increases.
• **Density: The densities of s-block elements is relatively low due to their large size.
• **Photoelectric effect: The s-block elements shows photoelectric effect. They emit electrons from their surface, when they come into the contact of light. Lithium is an exception here because of its higher ionization enthalpy.

Chemical Properties of s-block Elements

Now, it's time to learn about the chemical properties of S-block elements:

• **Reactivity: S-block elements are highly reactive in nature. Group 1 elements especially Na and K are well-known for their high reactivity with water that results in producing hydrogen gas & hydroxides. Group 2 metals are less reactive as compared to Group 1 elements but still they show a notable reactivity when exposed to air or water.
• **Formation of Compounds: S-block elements have high tendency to make compounds. They donate their electrons to form ionic compounds. Group 1 elements donate 1 valence electron while Group 2 elements donate 2 valence electrons to form a compound.
• **Reducing Agents: Due to the strong tendency of loosing electrons, s-block elements are known as strong reducing agents.

Atomic Mass of s-block Elements

• Atomic mass is the total mass of the protons & neutrons in an atom of the element. It is denoted by atomic mass per unit i.e. a.m.u or g/mol.
• Atomic mass of S-block elements refers to the average mass of the atoms of a particular element, taking into account the various isotopes and their relative abundances in nature.
• Atomic masses of the s-block elements changes as we go down the groups. The number of protons & neutrons increases and that's why the atomic mass also increases.

s-block Elements & Their Atomic Masses

The table added below shows the s-block elements and their atomic mass

Diagonal Relationship of s-Block Elements

Diagonal relationship is the relationship which shows a similar behavior between certain elements. These elements are located diagonally across each other within the same group but different periods of a periodic table.

For example. Lithium (Li) and Magnesium (Mg) have a diagonal relationship. Due to their similar ionic sizes and electronic configurations, they show similarities. Even after being in different periods, they have a very similar size of ions which forms a diagonal relationship between them.

Some of the similarities observed in these diagonal relationships include:

• **Similar Ionic radii- Certain elements have remarkably similar ionic sizes. For example, Lithium (Li) and Magnesium (Mg} & Beryllium (Be) and Aluminum (Al).
• **Common chemical behavior- Diagonal elements show similarity in their chemical reactions. For example, Lithium (Li) and Magnesium (Mg} & Beryllium (Be) and Aluminum (Al).
• **Complex formation- Due to their anonymous charge densities and electronic configurations, diagonal elements form similar kind of complexes. For example, Lithium (Li) and Magnesium (Mg}.
• **Oxidation state- Diagonal elements tend to show similar oxidation state in some cases. For example,Beryllium (Be) and Aluminum (Al).

Periodic Trends in s-Block Elements

S-block elements show several kind of periodic trends. As you move down to the group:

• Atomic size of the elements increases due to the addition of electron shells.
• Metallic character of the s-block elements follows a certain pattern from left to right. The elements on left like Alkali metals easily lose electrons and shows strong metallic properties. While the elements on right like halogens and noble gases have more non-metallic traits. This happens due to the decreasing atomic sizes.
• As you move down the group, the reactivity of s-block elements increases due to the increase in their atomic sizes.
• Due to the increasing atomic size & shielding effect, the s-block elements need less energy to remove electrons which results in the decline of ionization energy.

Compounds of s-block Elements

Here are preparations & properties of some important compounds of S-block elements:

**Sodium Hydroxide (NaOH)

• **Preparation: Sodium hydroxide is generally prepared through the electrolysis of aqueous sodium chloride or via the reaction of sodium carbonate with calcium hydroxide.
• **Properties: It is a white solid with high solubility in water and form a strongly alkaline solution. It is a strong base which is used in various industries such paper production, detergents, and in the chemical industry.

**Calcium Carbonate (CaCO 3 )

• **Preparation: Calcium carbonate is naturally occured and can be obtained from limestone, chalk, or marble. It's also prepared through precipitation reaction by mixing calcium chloride & sodium carbonate.
• **Properties: It is a white, odorless powder with a variety of applications such as cement production, diet supplement, plastic manufacturing and as a filler in paints and coatings.

**Read More,

• Important Compounds of Sodium
• Important Compounds of Calcium

Sample Questions on s-Block Elements

**Q1: Determine the atomic mass of following elements:

• **Na
• **Ra

**Solution:

Atomic mass of the given elements is,

• Na= 6.94 a.m.u.
• Ra= 226 a.m.u.

**Q2: Which of the following is alkaline earth metal?

1. **Sodium
2. **Potassium
3. **Radium
4. **Francium

**Solution:

Option is ****(3) Radium** is Correct. Radium is an alkaline earth metal.

**Q3: Write the electronic configuration of following s-block elements:

• **Calcium
• **Francium
• **Helium

**Solution:

Electronic configuration of following s-block elements is:

• Calcium= [Ar]4s2
• Francium= [Rn]7s1
• Helium= 1s2