What is the relationship between melting point and atomic radius and electronegativity and ionislzation energy?

Answer 1

It's a matter of the electrons that orbit the nucleus of the atom. The further down the column, the more shells of electrons the Nucleus has, and all of the Alkali metals have only one electron on their outer shell. All atoms "want" to have a full outer shell, so they try and get rid of the outer electron. The further away from the nucleus, the weaker the attraction to the said electron is (and the further away, the more shells). So, as you progress down the column of alkali metals, the attraction becomes weaker and the atom becomes more reactive.

Answer 2

As the element moves down the Periodic Table it has a larger atomic radius, so it has a weaker force of attraction between two atoms that are next to each other, as the centres are further apart. This means less energy is required to break the bonds between them resulting in a lower melting point.

Answer 3

A very general rule of thumb is that as atomic radius increases, melting point goes down. It's an inverse relationship. And atomis radius (generally) increases moving down the columns of the periodic table. As atomic radius increases, the atoms lose their ability to "stick together" and resist a change of state. Smaller atoms require more heat to melt or boil (vaporize) them because their smaller radaii allows the "reach" of the electrostatic charge of the nucleus to "get a bit of a grip" on the electrons of neighboring atoms. With a slight increase in electrostatic "clingyness" between atoms, more energy is required to separate them to cause a change of state. Smaller atoms resist melting better than larger atoms.

Answer 4

The melting point of a substance is determined by the intermolecular forces of a compound in question. The stronger and more prevalent these forces are, the higher the melting point will be. This is due to the strength of intermolecular forces overpowering the average kinetic energy of the molecules (temperature).

That being said, one must first determine the type of forces present. It seems by the wording of your question that you are likely considering the melting point of ionic compounds.

An ionic compound is held together by ion-ion bonds and thus charge plays an important role. Consider the ion flouride (F-) as compared to chloride (Cl-). The chloride ion is lower in group 7 than flouride due to the present of 8 extra electrons. Both ions have a negative 1 charge, however their surface areas are quite different. Flouride being much smaller than chloride has less surface area to distribute the -1 charge. Chloride on the other hand has more surface area due to its size and as a result the -1 charge is more dispersed than on the flouride ion. Because flouride has a stronger charge distribution, it is more attracted to cations than the chloride ion. Evidence of this can be seen with the salts sodium fluoride (m.p. 993C) compared to sodium chloride (m.p. 801C).

Electronegativity is the strength of electron pulling, the stronger the value the stronger an atom is able to pull electrons towards itself. Because an ionic bond is characterized by the stealing of electrons, the stronger the affinity for electrons the stronger the bond will be and consequently the more energy that is required to break it. On the other hand atoms with low electronegativities easily give up their electrons, this is particularly strengthens cations. The general rule is that the higher the electronegativity of the anion and the lower the electronegativity of the cation, the stronger the bond. An example between Iron (II) oxide (mp. 1377C ) vs manganese (II) oxide (mp. 1945C). Iron has an electronegativity of 1.83 vs manganese at 1.55. Since both are cations, the lower maganese exhibits a stronger affinity to be a cation and thus the ionic bond is stronger.

Ionization energy is the amount of energy required to strip a molecule of 1 electron. The lower this barrier, the more probably a cation becomes more stable. A stronger stable cation exhibits a stronger bond as a result.

Electron affinity is the amount of energy required for a molecule to gain an electron. The lower this energy cost, the more stable an anion will become and thus the stronger the bond.