To summarize the whole thing, we can make the following conclusions.Īn ion consists of the electrons in its numerous shells and the nucleus. Across a period, the effective nuclear charge increases as nuclear charge increases. The effective nuclear charge decreases down the group due to increased shielding effect. It can also be used to explain how many nuclei can control the outer electrons. It can be defined as the repelling of an outer electron by the inner electrons. The reason being they have a full valence shell and thus can neither gain nor lose electrons. Fluorine has the highest electronegativity and noble gasses are not included in this. Across a period, the electron affinity increases as nuclear charge increases.ĭown the group, it decreases, as the nuclear charge decreases. This is a characteristic feature of nonmetals as they gain electrons to become anions. Electron AffinityĮlectron affinity can be defined as the tendency of an atom to accept an electron or an electron pair. Also, in group 14, the electronegativity of tin is higher than lead. The group 13 elements are an exception and thus the electronegativity increases from aluminum to thallium. But the atomic radii also increase diagonally causing some exceptions.Īlong the Period – Li> Be > B > C > N > O > F The reason being, new shells are being added and thus the nuclear charge decreases. In a group, the atomic radius increases down the group. The reason for the decrease is as nuclear charge increases, the force of attraction between the nucleus and the valence electrons also increases, and the nucleus holds the electron tightly, thereby decreasing the atomic radii. Across a period the atomic radius decreases, as the nuclear charge increases. The atomic radius is the distance between the atomic nucleus and outermost stable electron orbital of an atom which is at equilibrium. This causes the force of attraction between the valence electrons and the nuclei increases, thereby inhibiting them from conducting electricity or heat. Since the valence electron is loosely bounded by the nuclei, they are able to conduct electricity well.īut across a period, the metallic character decreases as nuclear charge increases. The metallic properties increase down the group as the nuclear charge decreases down the group. Metallic property of an element can be defined as their ability to conduct electricity. They require a little less energy than the usual trend. Pseudo filled or half-filled valence shells have high ionization energy.Ī simple principle that can be used is that, if the principal quantum number is low, then the ionization number will be high for the electron present in that shell.Īll the elements in the oxygen and boron family are an exception to the above stated periodic trend. Thus, with an increase in atomic radius the ionization decreases. Shielding effect increases as nuclear charge increases, thus with an increase in shielding effect the ionization energy also increases.Īs the atomic radius increases the force of attraction between the nucleus and valence electrons also decreases. Lower the nuclear charge lower is the force of attraction between the nucleus and valence electrons, thus low ionization energy. Various Factors that Affect the Ionization Energy Levels The reason behind this is, down the group the valence electrons go farther away from the nucleus, thus the nuclear charge decreases. The reason behind this is that the nuclear charge across the period increases and thus the electrons are strongly held by the nucleus.īut as one goes down the group, the ionization energy decreases down the group. “Minimum energy required by an isolated atom to remove one electron in its neutral or gaseous state”Īs one goes across the period, the ionization energy increases. The ionization potential can be defined as, Later it was also found that the recurrence of properties was due to the recurrence of similar electronic configurations in the outer shells of atoms. He also stated that the periodic table was not just based on the atomic weights, but also based on various physical and chemical properties of elements. This principle was given by Dmitri Mendeleev. Elements having similar chemical properties re-occur in regular intervals” According to periodic law, “the chemical elements are listed in an order of increasing atomic number, and main properties thus undergo cyclic changes. Periodic law forms the basis for periodic trends. A few exceptions exist, for example, the ionization energy of groups 3 and 6. These trends arise due to changes in the structure of atoms of the elements within their groups and periods. \): The Chemistry of Photocopying.The specific patterns in the properties of chemical elements present in the periodic table are known as periodic trends.
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