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As we proceed down Group 17, the melting point and boiling point increases. This is because as we go down the group, the size of the molecules increases, thus resulting in an increase in the strength of the van der Waals forces (London forces), which is due to an increase in the size of the electron cloud. Thus, the melting point and boiling point of elements in Group 17 increases as we proceed down the group.

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Going down Group 1, the melting point and boiling point of elements decreases. This is because as we down the group, the atomic radii increase. The larger atomic radii of the metal ions result in a weaker metallic bond between the positively charged metal ions and the delocalised valence electrons, resulting in a decrease in the melting and boiling point for elements going down Group 1.

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When temperature increase, it will decrease the conductivity in conductors because electrons will be scattered away as electrons absorbs heat energy and convert it to kinetic energy, increasing its speed.

For semiconductor, when temperature increase, some valence electrons that are unable to jump to conduction band can jump across because they absorb more energy to jump to conduction band. thus semiconductor will be more effective when temperature increases.

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As the temperature of a semiconductor increase, the conductivity of a semiconductor increases. This is because for semiconductors, there is a narrow band gap that electrons of semiconductors have to gain enough energy in discrete quanta in order to arrive at the conduction band. Thus, when temperature increases, the energy supplied to electrons increase, thus resulting in more electrons being able to gain enough energy in order to jump across the band gap to reach the conduction band.

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As the temperature of a conductor increases, the conductivity of the conductor decreases. This is because a higher temperature results in more energy being supplied to the positively charged metal ions and delocalised electrons in the metallic lattice, thus increasing the vibration of the delocalised electrons and result in a scattering of the delocalised electrons, disrupting the number and position of electrons located in the conduction band.

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When ionic radius increases, metallic bond decreases as distance between nucleus and valence electrons increases, thus resulting weaker attraction forces.

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Atomic size affects electrical conductivity, as a smaller atomic size directly results in a higher electrical conductivity. This is because a smaller ionic radius of the metal ion results in stronger attraction forces between the metal ion and the valence electrons, resulting from a higher charge density, and thus the metallic bond will be stronger due to the stronger attraction forces. For example, the metallic bond of sodium, Na, is stronger compared to potassium, K, because the ionic radius of sodium is smaller compared to potassium.

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Lor Yuan & Xinhong

As number of valence electrons increase, the strength of metallic bond will increase because there are more negatively-charged delocalised valence electrons to form metallic bonds with positively-charged metal ions of the same element

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Valence electrons affect metal conductivity, as a higher number of valence electrons result in a higher charge and more delocalised electrons. Therefore, more delocalised electrons result in stronger attraction forces between the delocalised electrons and the more positively-charged metal ions, directly resulting in stronger metallic bonds. For example, aluminium has 3 valence electrons whereas sodium only has 1 valence electron. Thus, the metallic bond of Al is stronger compared to Na.

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As temperature of conductor increases, the electrical conductivity decreases. On the other hand, as the temperature of semiconductor increases, the electrical conductivity increases. Lim Ray Yuan

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When the number of valence electrons increases, strength of valence electrons increases, as more delocalised electrons form stronger attraction forces and metallic bonds.

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Size of the metal ion increase, distance between nucleus and valence electron increase, force of attraction between nucleus and valance electron decrease