The periodic table is arranged in rows and columns; the rows are called periods, and the columns are known as groups. Thus, the elements are arranged in ascending order of atomic number, which represents the number of protons in the nucleus of the atom.
This arrangement, in turn, reflects patterns in the chemical and physical properties of the elements, allowing them to be grouped into different blocks. In this way, the table not only provides an organized structure, but also makes it easier to understand the relationships between the elements.
The periodic table is divided into four main blocks:
- Block s
- Block p
- Block d
- Block f
Additionally, one can also consider an additional block that includes the inner transition elements, which are located in the two rows at the bottom of the periodic table.
Next, we will analyze each of these blocks in detail.
Block s
The s block is located on the left side of the periodic table and includes groups 1 and 2, as well as hydrogen and helium. Elements in this block are those that have electrons in their s orbitals.
Features of block s:
- Elements : Includes the alkaline metals (group 1), the alkaline earth metals (group 2), hydrogen (H) and helium (He).
- Electron configuration : S-block elements have their outermost electron shell occupied by one or two electrons in an s orbital. For example, lithium (Li) has the electron configuration 1s² 2s¹.
- Properties : The s-block metals are generally soft, have low melting points (except lithium), and are highly reactive, especially the alkali metals, which react vigorously with water.
- Industrial Use : Sodium and potassium are examples of S-block metals that are essential to biology and industry. Sodium is used in the manufacture of chemicals and as a preservative, while potassium is essential for plant growth.
Block p
The p block is located on the right side of the periodic table and includes groups 13 to 18. Elements in this block have electrons in their p orbitals.
Features of p block:
- Elements : Includes metals, nonmetals and metalloids. Examples are carbon (C), nitrogen (N), oxygen (O) and the halogens (F, Cl, Br, I), as well as the noble gases (He, Ne, Ar, Kr, Xe, Rn).
- Electron configuration : p-block elements have their outermost electron shell occupied by between one and six electrons in a p orbital. For example, oxygen (O) has the configuration 1s² 2s² 2p⁴.
- Properties : The properties of p-block elements are very diverse. P-block metals are generally less reactive than s-block metals, while nonmetals (such as oxygen and nitrogen) are essential for life. Noble gases are inert and do not react readily with other elements.
- Industrial use : Many p-block elements have significant industrial applications. Oxygen is used in respiration and combustion processes, silicon is essential in the electronics and semiconductor industry, and carbon is a key component in many organic compounds.
Block d
The d block is located in the center of the periodic table and includes the transition elements, which correspond to groups 3 to 12. These elements have electrons in their d orbitals.
Block d features:
- Elements : Includes transition metals such as iron (Fe), copper (Cu), nickel (Ni) and gold (Au).
- Electron configuration : d-block elements have their last electron shell occupied by electrons in a d orbital. For example, iron has the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s².
- Properties : Transition metals are known for their ability to form compounds with various oxidation states, which gives them great versatility in chemical reactions. In addition, they usually have high electrical and thermal conductivity, as well as high melting and boiling points.
- Industrial use : Transition metals are essential in the manufacture of alloys, catalysts, and in the production of electricity through fuel cells. For example, platinum is used as a catalyst in vehicles to reduce emissions.
Block f
The f block is located at the bottom of the periodic table and includes the lanthanides and actinides. These elements have electrons in their f orbitals.
Features of block f:
- Elements : Includes the lanthanides (La to Lu) and the actinides (Ac to Lr). Examples are neodymium (Nd) and uranium (U).
- Electron configuration : Elements in the f-block have their last electron shell occupied by electrons in an f orbital. For example, uranium has the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 5d⁹ 6p⁴.
- Properties : Lanthanides are known to be soft metals with high conductivity. Actinides, on the other hand, include radioactive elements such as uranium and plutonium, which are important in the nuclear industry.
- Industrial use : Lanthanides are used in permanent magnets and in the manufacture of certain types of lasers. Actinides, especially uranium and plutonium, are used as fuel in nuclear reactors.
Importance of blocks in chemistry
Dividing the periodic table into blocks is essential to understanding the chemistry of the elements. Each block reflects the electronic characteristics of the elements, which in turn relates to their chemical properties.
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Property prediction : By knowing which block an element is in, chemists can predict how it will behave in chemical reactions. For example, s-block elements tend to lose electrons easily, while p-block elements may gain or share electrons.
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Trends in the Periodic Table : Properties of elements, such as atomic radius, electronegativity, and ionization energy, show trends across periods and groups. These trends are most evident when considering the blocks of the table.
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Classification of elements : The division into blocks helps to classify the elements into metals, non-metals and metalloids, which is essential for the study of inorganic chemistry.
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Development of new materials : Understanding the properties of different building blocks allows scientists to develop new materials with specific characteristics. For example, research into semiconductor materials is based on the chemistry of p-block elements, while the creation of metal alloys is based on d-block transition metals.
How to know the block of an element?
Determining the block of an element on the periodic table is a fairly simple process if you understand the structure of the table and how electrons are distributed in atomic orbitals. Here are the steps to follow:
1. Identify the atomic number
The first step is to know the atomic number of the element, which is the number found at the top of each box on the periodic table. This number indicates the number of protons in the nucleus of the atom and therefore also the number of electrons in a neutral atom.
2. Observe the electronic configuration
The electron configuration of an element describes how the electrons are distributed in their orbitals. Each element has an electron configuration that can be deduced from its position on the periodic table.
3. Determine the block according to the orbitals
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s-block : Includes elements whose last electron is in an s orbital. These are the elements of groups 1 and 2, as well as hydrogen and helium. For example, lithium (Li) has the electron configuration 1s² 2s¹, which indicates that it belongs to the s-block.
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p-block : Comprises elements that have their last electron in a p orbital. This includes groups 13 to 18. For example, oxygen (O) has the configuration 1s² 2s² 2p⁴, so it belongs to the p-block.
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d-block : Contains the transition metals, whose electrons are in a d orbital. This covers groups 3 to 12. An example is iron (Fe), whose configuration is 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁶ 4s², indicating that it belongs to the d block.
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f-block : Refers to the lanthanides and actinides, which have their last electron in an f orbital. These elements are found in the two rows at the bottom of the periodic table. For example, uranium (U) has the configuration 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 4p⁶ 5s² 4d¹⁰ 5p⁶ 6s² 5d⁹ 6p⁴, indicating that it is an f-block element.
4. Use the position in the table
If you don't have the electron configuration handy, you can also determine the block of an element by looking at its position on the periodic table:
- Block s : First two columns on the left (group 1 and 2, plus H and He).
- Block p : Last six columns on the right (group 13 to 18).
- Block d : Central columns (group 3 to 12).
- Block f : Separate rows at the bottom of the table (lanthanides and actinides).