Atomic Structures of Elements and Materials

In engineering and science, we are dealing with different kinds of properties and features of materials. The main reason for these properties and features is atomic structures. Before understanding the general nature of materials, we need to understand the atomic structure of elements and materials. Here you can find detailed information about this topic. The general topics that we cover here;

  • General concepts about atomic structures of elements,
  • Atomic models,
  • Electron configurations,
  • Periodic table,
  • Element and material examples,
  • Frequently asked questions about atomic structures of elements and materials.

Check and read all the articles to understand the general principles of atoms.

Fundamentals of Atomic Structures of Materials

Atomic structure diagram.
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In materials science and engineering, the general features of molecules and materials are the result of the behavior of the sub-atomic particles. Around these particles, there are protons, neutrons, and electrons.

We can find the protons and neutrons at the center of the atomic structure. Also, the electrons are spinning around the center or core of the atoms. The protons and electrons are electrically charged. And also, you can understand from its name that, neutrons are not charged. They are neutral.

The electrical charge of the protons and electroncs are 1.6×10^-17 Coulomb. This value is positive for protons and negative for electrons.

Also, the protons, neutrons, and electrons have masses. These masses are infinitesimally low if we compare them with normal objects in our lives. Protons and neutrons have the same masses which is 1.67×10^-27 kg. The electrons are lighter than the protons and neutrons which have 9.11×10^-31 kg. 

Atomic Number of Materials and Elements

We generally arrange the materials according to their atomic numbers. So, generally, atomic numbers are very important for us. The symbol of the atomic number is Z. For electrically neutral atoms, the atomic number is equal to the number of electrons.

For example, the atomic number of Hydrogen is 1. Because Hydrogen elements have only 1 electron in them. Also, the atomic number of Uranium is 92. This means Uranium has 92 electrons inside the atomic structure. And also, Uranium is the last element that can occur naturally in nature.

Atomic Weight and Atomic Mass

People generally confuse these two concepts about atomic structures of elements. Firstly we need to understand the atomic mass. The symbol of atomic mass is A and atomic mass means the total number of protons and neutrons in the core.

We generally exclude the masses of electrons in atomic mass. Because the masses of electrons are very low. So, it is sufficient to consider the masses of protons and neutrons for an atom.

Before understanding the difference between the atomic weight and the atomic mass, we need to understand the isotope notion. The isotopes of an element mean the same elements but have different atomic masses. This difference may be the result of the extra protons or deficiency of protons in atomic structures of elements.

So, the atomic weight notion gains its importance here. The atomic weight is the average of the atomic masses of natural isotopes of elements.

In the definition of atomic weight, they use the atomic mass unit(amu) which is 1/12 of the most common isotope of the carbon atomic mass.


Mole is also a very important term in chemistry and materials science and engineering. We use Avogadro’s Number which is 6.023×10^23. There are 6.023×10^23 atoms in a one-mole substance. So, atomic weight gains its importance here.

The weight of the one-mole substance is directly correlated with atomic weight.

For example, the atomic mass unit of iron is 55.85 per iron atom. So, we can say that one mole of a pure iron substance is 55.85 grams. You can understand that Avogadro’s Number is a correlation between the atomic mass unit and the mole notion.

Different Atomic Models for Atomic Structures of Materials

In the intermolecular relation, the behaviors of electrons are very important. We need to understand this behavior to understand the interatomic or intermolecular relations. Because these relations create the general mechanical and physical properties of materials. Throughout history, there are different kinds of atomic models explained by different scientists.

Firstly, we need to state that, the scientific branch that deals with the sub-atomic particles and their behaviors of them is quantum mechanics.

Dalton’s Atomic Theory on Atomic Structures

The general studies to understand the atomic strıctures and behaviors of materials and elements may be started with this theory.

According to Dalton’s theory, every element and material is made up of atoms. And these atoms are indivisible structures. By dividing a matter in half and half, the atoms are the last point of this process.

The differences between elements are because of the differences in atoms. The mass of the atoms changes by different elements. In chemical reactions, the arrangements of atoms change.

Dalton’s theory is very primitive to explain the isotopes of atoms in nature. We can not understand anything about the atomic structures of elements from this theory. Also, after this theory, there are lots of other sub-atomic particles are discovered.

Thomson’s Atomic Model

This is the second important atomic model to understand the atomic structures of elements and materials. This is a very important scientific study of that Nobel-winning discovery of electrons.

According to the experiments, Thomson stated that atoms are positively charged structures where the negatively charged electrons are embedded inside them. This is a renowned explanation of the atom as a plum pudding model. According to this model, electrons are described as plums in a pudding.

Also, around the general limitations of this model, the stabilities of atoms and elements are can not be explained. And also, other advanced discoveries about sub-atomic structures can not be explained with Thomson’s theory.

Atomic Structure Theory of Rutherford

This is also a very important scientific study to understand atomic structures. The most important discovery is that most of the space in an atom is empty. So, the sub-atomic particles do not take up lots of space. The mass of the atom is concentrated at the center.

The structure of the atom is spherical according to this theory. And electrons are revolving around circular orbits.

The general limitations of Rutherford’s theory, the revolving energy of the electrons are not explained. Because electrons need constant energy to revolve around the nucleus. But if this energy finishes, the electrons will fall on the nucleus.

Bohr’s Atomic Model on Atomic Structures

Image Source: Wikimedia.

This is maybe the first science-based definition of the behaviors of electrons in an atom. According to this model, electrons are spins in the orbitals. These orbitals are around the nucleus of the atoms. The nucleus of atoms constitutes the protons and neutrons.

Also, according to Bohr’s atomic model, electrons can have only specific energy levels. The places of orbitals are defined according to these energy levels. So, electrons can not constitute the intermediate energies between these specific energy levels. Also, we call these energy levels quantized energy levels.

For example, there are different orbitals in an atom. If you want to take an electron from deeper levels of orbitals to outer levels, you need to give specific energy to these electrons. Also, we need to give specific energies to these electrons to make them free electrons.

Wave and Mechanical Explanations of Electron Movements

In some cases, Bohr’s explanations are not sufficient. There is another model that explains the movements of electrons. This model approaches electrons as they are moving as waves and also act as mechanical particles. So, we can not give the exact specific places of electrons around the nucleus.

So, there are places of atoms that have the probability to exist. We call this phenomenon an electron cloud. We can not observe the exact location of the electron because of this wave-mechanical explanation.

Quantum Numbers to Explain the Place of Electrons in Atomic Structures

The last energy states.

Above Bohr’s atomic and electron model, these quantum numbers and shell definitions state the behavior of electrons in a more specific and detailed way. To define the location and the energy level of an electron, we use different quantum numbers.

Firstly, we need to start from the first quantum number which is the same as the energy levels of Bohr’s atomic model. Also, we call this quantum number a principal quantum number. The symbol of this quantum number is ‘n’.

Also, principal quantum numbers have subshells. Also, their subshells have specific energy levels where electrons can reside in. These subshells are;

s subshell: This is the first subshell or energy level can which electrons reside. In the s subshell, there is only one energy level.

p subshells: p subshell is the second energy level in principal quantum numbers. In the p subshells, there are three energy levels or energy states.

d subshells: Third energy level which includes five energy states.

f subshells: This is the last one that has seven energy states.

Subshells and Electrons

But we need to state that, each principal quantum number does not include all the subshells. There is an order. Check below to understand the order between the shells and subshells in atomic structures.

Principal Quantum Number, nShellSubshellsNumber of Energy StatesNumber of Electrons

1 K s 1 2

2 L s, p 1, 3 2, 6

3 M s, p, d 1, 3, 5 2, 6, 10

4 N s, p, d, f 1, 3, 5, 7 2, 6, 10, 14

Electron placement according to shells and subshells.

So, this is the general electron placement of the shells and subshells in atoms. According to the number of electrons in atoms, electrons place like above.

The first layer or first shell can contain only 2 electrons which have only the s subshell. Also, the second principal quantum number can have 8 electrons. And have s and p subshells. The third shell has s, p, and d subshells which can have 18 electrons in it. The fourth one has s, p, d, and f subshells. And the number of electrons is 32.

Also, from bottom to top, the energy levels of electrons increases in general.

Electron Configurations in Atomic Structures

Atomic structures.

Also, the electron configurations are very different in atomic structures. As you can see in the table above, each specific energy state can have two electrons at the same time. This is the Pauli exclusion principle which states that each energy state can have two electrons in different spins.

The electron placement is take place in atoms according to the energy states. Electrons start to fill the energy states from the lowest energy states to higher ones. So, the electron configuration is defined according to this.

So, let’s check the example below to understand the general electron configuration of atoms.

For example, the electron configuration of Krypton which has atomic number 36; 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6

So, as you understand that we show the principal quantum number, the subshell of this number, and several electrons for each energy level of atoms.

Importance of Valence Electrons

Valence electrons are very important. Valence electrons are the electrons that stay at the outermost shell of the atomic structure. For example, the valence electrons of the Krypton atom are 4s2 and 4p6.

Valence electrons are very important in the chemical reactions and chemical and physical properties of atoms and molecules. They are directly responsible for chemical reactions between atoms.

Periodic Table to Understand the Atomic Structures

Periodic table for atomic structures.
Periodic table.

They are a very important directory to classify atoms according to their atomic structures. With a periodic table, we obtain a meaningful classification of atoms according to their physical and chemical properties.

If we take a look at the general structure of periodic tables, there are seven rows in which the atoms and elements are arranged according to the increasing atomic numbers. Also, each column of the periodic table contains the same valence structures of atoms.

So in each column, we can find the same atomic structures and physical and chemical properties.

Groups of Periodic Table

We call the column groups in periodic tables. Also, if we take a look at the general properties of these groups,

  • Group 0: This is the group of inert gases. Because the outermost shells are filled with electrons fully. Because of this property, this group of atoms has zero chemical affinities.
  • Group 1A and 2A: These groups are the leftmost columns of the periodic table. In the valence structures of these elements, there are one and two electrons. Also, we call them alkali metals or alkaline earth metals.
  • Group 3B to 2B: After groups, 1A and 2A, the arrangement of columns are 3B, 4B, 5B, 6B, 7B, 8B, 1B, and 2B from left to right. We call these groups of elements as transition metals. Because all the elements here are metals. The last electron state is d for transition metals and these last energy states are partially filled.
  • Groups 3A, 4A, and 5A: These elements have intermediate characteristics between the nonmetal and metals because of their valence electron structures.
  • Groups 6A and 7A: These groups of elements have one and two electrons that are deficient at the last energy state of shells. In general, they show stable chemical structures. Also, we call them halogens.

As you understand, the classification of different elements in periodic tables is very simple.

Electropositivity and Electronegativity of Elements

These two terms are also very important in the chemical reactions between the elements. Electropositive elements are prone to take electrons to be electrically negative ions. These elements are taking electrons to complete the valence energy state to become stable.

Also, electronegative elements are trying to give their redundant electrons to become stable.

In the periodic table, from right to left, the electropositivity decreases, and electronegativity increases. So, periodic tables are very important indicators of the possible chemical reactions between the elements.

So, we can use the periodic tables to understand the atomic structures of materials and elements in a better way.

The General Atomic Structures of Important Elements

We can understand the general atomic structures by checking these important elements for different applications. Our first example is Carbon.

The Structure of Carbon

Carbon is a very important element for us. Because it is a general element that forms various kinds of bonds with different elements. This very high variety of chemical affinity produced the life forms. All of us and nature are made with carbon and carbon-based moılecules.

Also, carbon is very important in materials science. Carbon is the main element that we are adding to the iron to obtain different iron-carbon systems. According to the changing carbon content, we obtain different kinds of steel and cast irons.

If we take a look at the atomic structure of carbon, the valence shell has four electrons. The valence shell is the second shell for the carbon atom. So, the valence shell takes 8 atoms. This provides a very high variety of chemical reactions.

Atomic Structure of Oxygen

Also, Oxygen is a very important element for nature and engineering applications. We use the different oxides of elements such as aluminum oxides in refractory applications. Aluminum is not a refractory element that melts in around thousands of degrees of temperature. But aluminum oxides can stay stable in very high temperatures.

The atomic number of the Oxygen is 8 and the atomic mass is 16. 6 electrons are the valence electrons of oxygen which is prone to take electrons. So, oxygen is an electronegative element.


These are the general explanations of general terms of atomic structures of materials and elements. To understand the mechanical and physical properties and features of materials, we need to understand the fundamentals of atomic structures of elements. Atomic structures are the most important factor in the properties.

Also in history, there are different atomic models explained. In each atomic model, different properties are discovered by scientists. The closest model is the wave-mechanical model of the atomic structure that nearly explains all the phenomenons about sub-atomic structures.

And the structures of electrons and arrangement of electrons are very important in the explanation of atomic structures. There is a specific arrangement of electrons according to the energy levels. We can predict the general chemical behaviors of elements according to these features.

The periodic table is also very important to classify the atoms and elements according to these properties. You can use this table in different studies.

Do not forget to leave your comments and questions below about the atomic structures and atomic particles of elements and materials.

Your precious feedbacks are very important to us.

FAQs About Atomic Structures of Elements and Materials

What is the atomic structure of elements?

These structures explain the placements and features of sub-atomic particles such as electrons, neutrons, and protons. They are very important in the features of different elements and materials.

How to understand the atomic structure?

To understand it, you need to look at the general theories about atomic structures. If you understand these theories; Dalton’s atomic model, Thomson’s theory, Rutherford’s experiments, and Bohr’s theories, you will get a general idea about it.

How to understand the atomic structure?

The periodic table is the best for it. You can understand it by taking a look at the periodic table. There is a lot of important information about the atomic structures of elements in the periodic table. So, you can understand the general chemical situations of atomic structures.

How can atomic structure affect chemical bonding?

There is a strong relationship between chemical reactions and atomic structures. The valence electrons define the nature and the structure of the chemical bonding which is about the atomic structure.

What are electropositivity and electronegativity?

Electropositivity of elements is the affinity to take electrons into the valence shells. Also, electronegativity is the affinity of elements and atoms to discard electrons. Electronegative and electropositive atoms create the most solid chemical bonds.

What are the valence electrons?

Valence electrons are the electrons at the outermost shell of atoms. These electrons are responsible for all the chemical reactions that occur. Because of it, valence electrons and valence structures of elements and atoms are very important.


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