Main Difference – S vs P Block Elements

The periodic table of elements contains all elements that have been discovered so far. These elements are grouped into 4 major groups as s block, p block, d block and f block. They are categorized according to the orbital where their valence electrons are present. Furthermore, these elements can also be categorized as metals, nonmetals, and metalloids according to their physical properties. All s block elements except hydrogen are metals. Most p block elements are nonmetals. Rest of the elements in the p block are metalloids. The main difference between s and p block elements is that the valence electrons of the s block elements are in the s orbital whereas the valence electrons of the p block elements are in the p orbital.  

Key Areas Covered

1. What are S Block Elements
      – Definition, Characteristic Properties, Members
2. What are P Block Elements
      – Definition, Characteristic Properties, Members
3. What is the Difference Between S and P Block Elements
      – Comparison of Key Differences

Key Terms: Metals, Metalloids, Non-Metals, P Block Elements, S Block Elements, Valence Electrons

What are S Block Elements

S block elements are the elements that have their valence electrons in their outermost s orbital. Since s orbital can keep a maximum of only 2 electrons, all s block elements are composed of either 1 or 2 electrons in their outermost s orbital. Their electron configuration always ends with s orbital (ns).

Figure 1: Blocks in Periodic Table of Elements (s block is in pink color)

Except for hydrogen, all other members of s block are metals. Hydrogen is a nonmetal. But since it has only an s orbital, it is also categorized as an s block element. The groups 1 and 2 include s block elements. Elements in group1A are composed of one valence electron in the outermost s orbital whereas group 2 elements are composed of two valence electrons. Group 1 elements are named as alkali metals, and group 2 elements are alkali earth metals.

Helium is also an s block element since it has only an s orbital that is composed of 2 electrons. Therefore, Helium also has its valence electrons in s orbital and is categorized as an s block element. Helium is also a non-metal.

The oxidation states of s block elements can be either +1 or +2 (hydrogen sometimes have -1 oxidation state). This is because these elements can become stable by removing one electron (in group 1 elements) or two electrons (in group 2 elements).

The atomic radius of s block elements increases down the group due to the addition of a new electron shell after each period. The ionization energy decreases down the group since the atomic radius increases. This is because electrons in the outermost orbital are weakly attracted by the nucleus

Both melting point and boiling point decrease down the group as well. This is because the strength of the metallic bond decreases with the increase of atomic radius. Thus, metal atoms can easily be separated.

What are P Block Elements

P block elements are elements having their valence electrons in their outermost p orbital. P subshell can hold up to 6 electrons. Therefore, the number of electrons in the outermost p orbital of p block elements can be 1, 2, 3, 4, 5, or 6. Their electron configuration always ends with p orbital (np).

Most p block elements are nonmetals whereas few others are metalloids. From group 3 to group 8 includes p block elements except for Helium (Helium belongs to the s block as described above). The atomic radius of p block elements increase down a group and decrease along a period. The ionization energy decreases down the group and increases along the period. Electronegativity is also increased along the period. The most electronegative element is Fluorine which belongs to the p block.

Figure 2: Metalloids of the p Block

Most p block elements show allotropy. Allotropy refers to different forms of molecular structures of the same element. The oxidation states of p block elements may vary depending on the number of valence electrons present in their atoms. Some elements may have only one oxidation state whereas other elements have several oxidation states.

group 8 of the p block is composed of noble gases. These elements are inert gases and cannot undergo chemical reactions unless in extreme conditions. Noble gases have the most stable electron configuration and their p orbitals are completely filled with electrons. Group 7 elements are called halogens. Almost all elements in the p block form covalent compounds and can also take part in ionic bonds.

Difference Between S and P Block Elements

Definition

S Block Elements: S block elements are elements having their valence electrons in their outermost s orbital.

P Block Elements: P block elements are elements having their valence electrons in their outermost p orbital.

Oxidation States

S Block Elements: S block elements can have 0, +1 or +2 oxidation states.

P Block Elements: P block elements show a number of oxidation states varying from -3, 0 to +5 (stable oxidation states).

Chemical Bonding

S Block Elements: S block elements form metallic bonds and ionic bonds.

P Block Elements: P block elements form covalent bonds or ionic bonds (with metals).

Metal Properties

S Block Elements: All s block elements are metals.

P Block Elements: Most of the p block elements are nonmetals, others are metalloids.

Electronegativity

S Block Elements: The electronegativity of s block elements is comparatively less.

P Block Elements: The electronegativity of p block elements is comparatively high.

Conclusion

S and p block elements are chemical elements found in the periodic table of elements. They are grouped as s block or p block according to the position of valence electrons in orbitals. The main difference between s and p block elements is that the valence electrons of the s block elements are in the s orbital whereas the valence electrons of the p block elements are in the p orbital. 

References:

1.”S-Block Elements on the Periodic Table: Properties & Overview.” Study.com. n.d. Web. Available here. 02 Aug. 2017. 
2.”P-block Elements.” P-block Elements Properties, P-block Elements Definition | [email protected] N.p., n.d. Web. Available here. 02 Aug. 2017. 

Image Courtesy:

1. “Periodic Table structure” By Sch0013r – File:PTable structure.png (CC BY-SA 3.0) via Commons Wikimedia 
2. “Periodic table (metalloids)” By DePiep – Own work (CC BY-SA 4.0) via Commons Wikimedia

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