Question

Describe how the metallic and non-metallic characters vary along a period and group of the periodic table.

Short answer

Answer: Metallic character generally decreases across a period (left to right) and increases down a group, while non-metallic character increases across a period (left to right) and decreases down a group. This variation is mainly due to changes in ionization energy and electron affinity, which are influenced by the nuclear charge and shielding effect experienced by valence electrons.

Step-by-step solution

Define metallic and non-metallic characters

Metallic character refers to the degree to which an element exhibits properties commonly associated with metals - such as being shiny, malleable, ductile, and conducting electricity and heat. On the other hand, non-metallic character refers to the ability of an element to display non-metal properties, which include poor conductivity, brittleness, and dull appearances. Elements with high metallic character tend to have lower ionization energy and electron affinity, while elements with high non-metallic character have higher ionization energy and electron affinity.

Variation of metallic character along a period

As we move from left to right across a period in the periodic table, the number of protons in the nucleus increases. This results in an increase in the positive charge experienced by the outer electrons, which are also drawn closer to the nucleus due to the increasing electrostatic forces. Consequently, the ionization energy and electron affinity increase as we move from left to right in a period. Due to these increasing values, the metallic character of elements decreases as we move across a period, while the non-metallic character increases.

Variation of metallic character within a group

In a group of the periodic table, the elements share the same number of valence electrons. As we move down a group, the number of electron shells increases, effectively increasing the distance between the nucleus and the outermost electron shell (the shielding effect). As a result, the electrostatic force of attraction between the nucleus and outer valence electrons decreases. Consequently, both the ionization energy and electron affinity decrease as we move down a group. Thus, the metallic character of elements increases as we move down a group, while the non-metallic character decreases.

Conclusion

In conclusion, the metallic character of elements within the periodic table generally decreases as one moves across a period from left to right and increases as one moves down a group. Conversely, non-metallic character increases as one moves across a period from left to right and decreases as one moves down a group. These trends are primarily due to changes in ionization energy and electron affinity as a result of variations in the nuclear charge and shielding effect experienced by the valence electrons.