It is very important for a chemistry student to have an understanding of the behavior and properties of the elements in the periodic table. But so far there are 118 elements in the periodic table. It is a great challenge to simultaneously understand the behavior and properties of so many elements. As there are problems, there are solutions. Chemists tried to find similarities between the elements to solve this problem. They observed that several properties of the elements change gradually from left to right of the same level in the periodic table, or from the top to the bottom of the same group. They change in such a way that the value of the next unknown element can be predicted. And this is only possible when we arrange the elements based on atomic number. Since the elements are arranged based on the atomic number in our periodic table, these periodic properties of the elements can be observed in the periodic table.
What are Periodic Properties?
The properties in which the atomic number of the elements in the same stage or group of the periodic table changes gradually as the atomic number increases are called periodic properties.
The periodic properties of the elements are-
- Size of atom
- Compatibility of atoms
- Ionization energy
- Electron addiction
- Electronegativity
- Metallic properties
- Melting point and boiling point
- Density of atoms
Among these periodic properties of the elements, there is again a new feature. That is – if the value of any of their properties decreases from the left to the right of the same level, it increases from the top to the bottom of the same group. Again, if the value of any of their properties increases from the left to the right of the same level, it decreases from the top to the bottom of the same group.
And thus based on periodic properties, it is possible to easily gain a lot of understanding about the elements, which is not possible in any other way.
What is the Size of the Atom?
Atomic size basically refers to the distance from the nucleus of the element to its last energy level or compatibility energy level. In simple words – the size of an element is the size of that atom.
Periodicity of Atomic Size
As one moves from the top to the bottom of the same group in the periodic table, its size increases. Because going down from the top of the same group means a new stage. That is the creation of one new energy level. As one new energy level is included, it can be said that the size of the atom is increasing. So we can say, the size of atoms increases from top to bottom in the same group of the periodic table.
Again, if we move from left to right of the same level, no new energy levels are created. But in this case, along with the increase in atomic number, one proton or positive charge in the nucleus and one electron in the last energy level increases. As they are oppositely charged, the force of attraction between them increases. As a result, the atom goes silent. As a result, the size of the atom becomes smaller. So we can say, the size of atoms gets smaller as we go from left to right of the same phase in the periodic table.
What is the Compatibility of Atoms?
The valence of an element is the number of unpaired electrons it has in its last energy level. An atom expresses an interest in giving up an unpaired electron in its last energy level or accepting another electron there to fill or pair an unpaired state. Sometimes, because the electronegativity of both elements is equal or close, they share electrons without exchanging electrons. In these cases, the number of electrons that are exchanged, given, or shared is the composition of the element.
Periodicity of the Atomic Compatibility
There is no change in the number of odd electrons in the last energy level as we move from the top to the bottom of the same group in the periodic table. Therefore, there is no change in the atomic compatibility when going from the top to the bottom of the same phase.
But as the number of last energy odd electrons increases from left to right of the same phase, so the valence also increases. But there is a limit to the acceptance or loss of such a large number of electrons. Again, if a new electron is added to the odd electron, the number of electrons may become even, so the coefficient may not increase. Even if it increases, it is not possible to gain or lose more than 4 electrons without some exceptions. To liberate so many electrons, the atom must be given a lot of energy, so that the atom can break. Therefore, if you go from left to right in the same phase of the periodic table, the probability of electron release increases. A phase goes to a maximum and then the electron acceptability decreases.
What is Ionization Energy?
A certain amount of energy is required to remove an electron from an atom of an element in the gaseous state an infinite distance and turn it into a positive ion. But since we cannot do this separately for an atom, we do this calculation for one mole of atoms. Then – the amount of energy required to remove one mole of electrons from atoms of an element in the gaseous state at an infinite distance and turn it into one mole of positive ions is called the ionization energy of that element.
The amount of energy required to convert the first mole of electrons from the element into one mole of positive ions is called the first ionization energy. The amount of energy required to take one more mole of electrons from the element and convert it into two moles of positive ions is called the second ionization energy. Similarly, the amount of energy required to convert one mole of electrons from an element into three moles of positive ions is called tertiary ionization energy. Thus the fourth, fifth, sixth, seventh, and eighth ionization energies are obtained.
In this case, since the element is deficient in electrons after receiving the first mole of electrons, more energy is required to take the second mole of electrons than the first mole of electrons. Similarly, since the molecule has a deficiency of two moles of electrons after taking the second mole of electrons, more energy is required to take the third mole of electrons. That is why the third ionization energy is higher than the second ionization energy. In this way, the ionization energy of the same element gradually increases.
Periodicity of Ionization Energy
The amount of energy required to gain electrons from elements in the periodic table, or how willing they are to give up electrons, depends on the atomic number distance of the nearest inert gas element from them. Because in nature, just as all matter tends to stay in the lowest energy state, elements also seek to acquire the electron configuration of the nearest inert gas. For example, sodium wants to give up an electron to gain the electron configuration of the nearest inert element neon, chlorine wants to gain an electron to get the electron configuration of the nearest inert element argon. So less energy will be required to take an electron from sodium, on the other hand, more energy will be required to take an electron from chlorine. And this is how the ionization energy increases from the left to the right of the same phase of the periodic table.
Again, as the size of the atoms increases from the top to the bottom of the same group, as the distance between the nucleus and the electron increases, the force of attraction between the nucleus and the electron decreases. Also, as the size of the atom increases, the nucleus cannot attract the electrons of the last energy level much due to the high density of intermediate electrons. As a result, less energy is required to take an electron from the last energy level. And in this way, the ionization energy of the elements decreases from the top to the bottom of the same group.
What is Called Electron Attachment?
Just as energy is required to remove electrons from an atom, energy is released from an element when electrons are given to it. Like ionization energy, since it is not possible to think of an atom separately, we will take one mole of atoms instead of one atom. Then – if one mole of an element in a gaseous state enters one mole of electrons into the gaseous atom and turns one mole into a single negative ion, the amount of energy released from that element is called the electron affinity of that element.
Periodicity of Electron Attachment
As the size of the atom increases, the electron affinity decreases. Electron affinity increases as the charge on the nucleus increases. Since the size of the element decreases from left to right of the same phase, electron affinity increases from left to right of the same phase. Again, going from the top to the bottom of the same group, as the size of the atom increases, the electron affinity also decreases.
What is Electronegativity?
In covalent bonding, the two atoms participating in the bond share an equal number of electrons to form the bond. Forms bonds and shares the electrons in the bond equally. If this bond is between the same atom, then the bonding electron is equally attracted by both atoms. But when this bonding occurs between different atoms, the bonding electron is more attracted to one of the atoms. This ability to attract shared electrons in covalent bonds is called electronegativity. That is, the ability to attract shared electrons in covalent bonds is called electronegativity.
Periodicity of Electronegativity
The electronegativity depends on how close an element can attract electrons to an inert gas element. Elements that have more electrons in their last energy level but are not full. Orbitals are filled only when they accept 2-1 electrons, they attract more electrons toward themselves. For example, sodium has only one electron in its last energy level. It needs 7 more electrons to complete the octave. And it is not possible to accept so many electrons. And so sodium wants to leave this last energy level electron. On the other hand, chlorine has 7 electrons in its last energy level. And if only one electron can be accepted, the octave will be complete. So attracts an electron more. Thus electronegativity increases from left to right in the same phase of the periodic table.
In this case, the electron is mainly attracted by the nucleus of the element. Moving from the top to the bottom of the same group in the periodic table, as the size of the atom increases, the ability of the nucleus to attract electrons decreases. As a result, the electronegativity also decreases.
What are Metallic Properties?
Elements that give up one or more electrons and become positive ions are called metals. This property of giving up electrons of metal is its metallurgy. The metallurgy of atoms is the more easily they can leave one or more electrons from their outer energy levels.
Periodicity of Metallurgy
Since the elements of the first group of the periodic table have only one electron in the last energy level, they easily leave it and acquire the electron configuration of the nearest inert gas and become positive ions. So their mental properties are more. In the case of the second group, the elements have two electrons in the last energy level, which is more energetic than the first group left. Therefore, their metallurgy is slightly less than the first group. Thus the metallurgy of the elements decreases from the left to the right of the same phase of the periodic table.
Again, since the easier it is for the electron to leave, the more active metal is, so the size of the atom increases from the top of the same group of the periodic table, so the attraction of the nucleus on the electron of the last energy level is relatively less. As a result, they can easily release the last energy-level electron. Therefore, going from top to bottom of the same group, the metallicity increases as the atomic size increases.
What is the Melting Point?
The temperature at which a solid substance melts into a liquid is called the melting point of that substance. For example, ice melts and turns into the water at a temperature of 0 degrees Celsius. So melting point of ice is 0 degrees centigrade.
What is the Boiling Point?
The temperature at which a liquid substance turns into a gaseous substance is called the boiling point of that substance. For example, the water turns into steam at a temperature of 100 degrees Celsius. So the boiling point of water is 100 degrees centigrade.
Periodicity of Melting and Boiling Points
Elements increase in size as you go from top to bottom of the same group in the periodic table. At the same time, their electron density decreases. As the density decreases, the melting and boiling points of the elements also decrease. Again, the size of the elements decreases from the left to the right of the same level. At the same time, the density of electrons in them increases. As a result, the melting and boiling points of the elements increase.
Density of Atoms
Atomic density basically refers to the density of electrons in an atom. Atomic density is the characteristic of how close together the electrons are in an atom or the number of electrons per unit volume.
Periodicity of Atomic Density
As we have seen in the form of atoms, if we move from left to right of the same phase of the periodic table, the energy level of the atom does not increase, as the number of electrons increases in the last energy level, the attraction between the nucleus and electrons increases by increasing the charge of the atom. As a result, the atoms become silent and the size of the atom becomes smaller. In this case, at the same time, the number of electrons in the atoms increases, and the size of the atoms decreases, so the density of electrons in the atoms increases. That is the atomic concentration increases from the left to the right side of the same phase.
As the size of the atoms increases from the top to the bottom of the same group in the periodic table, the electron density in the element decreases. As a result, the density of atoms also decreases. That is, the density of atoms decreases from top to bottom of the same group.
Written
Jeion Ahmed
Chittagong, Bangladesh
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