Periodic trend

Periodic trends are specific patterns that are present in the periodic table of chemical elements that illustrate different aspects of a certain element, including its size and its electronic properties. Major periodic trends include electronegativity, ionization energy, electron affinity, atomic radius, metallic character, and ionic radius. These trends exist because of the similar atomic structure of the elements within their respective group families or periods, and because of the periodic nature of the elements.

Electronegativity

Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. In the periodic table, electronegativity increases from left to right across a period and decreases down a group. This trend is due to the increase in nuclear charge across a period and the increase in distance between the nucleus and the valence electrons down a group.

Ionization Energy

Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The ionization energy tends to increase across a period and decrease down a group. This is because atoms are smaller across a period, so the outer electrons are closer to the nucleus and more tightly bound.

Electron Affinity

Electron affinity is the amount of energy released when an electron is added to a neutral atom or molecule in the gaseous state to form a negative ion. Generally, electron affinity increases across a period and decreases down a group, with some exceptions.

Atomic Radius

The atomic radius is a measure of the size of an atom. The atomic radius decreases across a period due to the increase in the positive charge of the nucleus, which pulls the electrons closer. Conversely, the atomic radius increases down a group as the number of electron shells increases.

Metallic Character

Metallic character refers to the level of reactivity of a metal. Metals tend to be good conductors of electricity and heat, are malleable and ductile, and have a high luster. The metallic character decreases across a period and increases down a group.

Ionic Radius

Ionic radius is the radius of an atom's ion. Cations (positively charged ions) are typically smaller than the atom from which they come, due to the loss of an electron shell. Anions (negatively charged ions) are typically larger than the atom from which they come, due to the addition of electrons in the outer electron shell which increases electron-electron repulsion.

Periodic trends are crucial for chemists to understand and predict the properties of elements and their compounds. These trends help in the study of chemical behavior, the development of new materials, and in various applications across the fields of chemistry and materials science.

Periodic trend Resources
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