Trends in the Peiodic Table

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Trends in the Periodic Table
* Generally, the atomic radius decreases across a period from left to right and increases down a given group. The atoms with the largest atomic radii are located in Group I and at the bottom of groups. Moving from left to right across a period, electrons are added one at a time to the outer energy shell. Electrons within a shell cannot shield each other from the attraction to protons. Since the number of protons is also increasing, the effective nuclear charge increases across a period. This causes the atomic radius to decrease.

The properties of the elements exhibit trends. These trends can be predicted using the periodic table and can be explained and understood by analysing the electron configurations of the elements. Elements tend to gain or lose valence electrons to achieve stable octet formation. Stable octets are seen in the inert gases, or noble gases, of Group VIII of the periodic table.. First, electrons are added one at a time moving from left to right across a period. * Atomic Radius

The ionisation energy, or ionisation potential, is the energy required to completely remove an electron from a gaseous atom or ion. The closer and more tightly bound an electron is to the nucleus, the more difficult it will be to remove, and the higher its ionisation energy will be. The first ionisation energy is the energy required to remove one electron from the parent atom. . Ionisation energies increase moving from left to right across a period (decreasing atomic radius). Ionisation energy decreases moving down a group (increasing atomic radius). Group I elements have low ionisation energies because the loss of an electron forms a stable octet.

* First Ionisation Energy

* Electron affinity reflects the ability of an atom to accept an electron. It is the energy change that occurs when an electron is added to a gaseous atom. Atoms with stronger effective nuclear charge have greater electron affinity. Some...
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