Melting and boiling points of elements in periodic table

Melting and boiling points are very important physical properties in chemistry. Different elements and compounds have different melting and boiling points. From values of melting and boiling points of elements, we can get a understanding of structure of elements, intermolecular forces between molecules and more.


IN THIS TUTORIAL,

  • Reasons for having different melting and boiling points of elements
  • Comparing melting and boiling points values of each group in periodic table
  • Melting and boiling points of organic compounds
  • Comparing melting and boiling points of different elements and compounds

Melting and boiling points of elements

Melting and boiling point variations are not clear (do not have uniform pattern) in periodic table. But we can see, some elements have higher melting and boiling points and some have less. Here we study melting and boiling points of s, p, d blocks elements.

IVAth group elements (C,Si) show high melting and boiling points because they have covalent gigantic lattice structures.


Are their any compounds don't have a melting point?

Yes. There are. Some compounds are not stable to heat. When heating a such compound, they decompose to another substance.

Example:

Nickel carbonate (NiCO3) decomposes to NiO and CO2 on heating.


Melting and boiling points across a period

In first three periods, there is a clear variation. Melting and boiling points are incresed upto the 4th group with when going to the right. Then it starts to decrease upto noble gases.


Why different elements and compounds have different melting and boiling points?

There are many reasons to effect for melting and boiling points of elements.

  • Molecular Mass
  • Intermolecular forces
  • Metallic lattice ( important in metals)

Lowest melting and boiling points elements in a period

Inert gasses have the lowest melting and boiling points element in period because their van der waals' forces are very weak.


Halogen and inert gases melting and boiling points

Melting and boiling points of both halogen and inert gases increases along the group.

melting boling points halogen and inert gases

Alkali metals melting and boiling points

Alkali metals(Li, Na, K, Rb, Cs) are soft and have low melting and boiling points. Alkali metals have only one valence electron per metal atom and therefore, the energy binding the atoms in the crystal lattice of the metal is low. Therefore, the metallic bonds in these metals are not very strong. So melting and boiling points decreases on moving down from Li to Cs.

Alkali metals melting and boiling points

Hydrogen

  • Melting point - -259.20C
  • Boiling point - -252.90C

Alkaline earth metals melting and boiling points

Alkaline earth metals(Be, Mg, Ca, Sr, Ba, Ra) have low melting and boiling points. But their melting and boiling points are higher than corresponding alkali metals in the same period due to comparatively smaller size. But melting and boiling points do not show regular trends.

Alkaline earth metals melting and boiling points

Why alkali metals have low melting points than alkaline earth metals?

Both alkali and alkali earth metals are in s block. We know alkali metals have only one valence electron per metal atom.

But alkaline earth metals have two valence electrons per metal atom.

alkali earth metals have low melting points than alkaline earth metals

Also alkali earth metals are small in size than alkali metals.

When number of valence electrons in the lattice increases, the metallic bond is strong. Also when atomic radius decreases, metallic bond become strong. Also Therefore metallic bonds of alkali earth metals are much stronger than alkali metals.

Therefore melting and boiling points of alkali metals are less than melting and boiling points of alkali earth metals



Alkali metals and alkaline earth metals melting and boiling points

melting boling points alkali and alkali earth metals

Boiling and melting points of group 13 elements

B, Al, Ga, In, Tl are the elements of group 13 elements. Melting and boiling points decrease on moving down the group. However, the decrease in melting point is not as regular as in boiler points. Ga has very low melting point(303K).

Boiling and melting points of boron, aluminium

Melting and boiling points of group 14 elements

The atoms of this group form covalent bonds with each other and therefore, there are strong binding forces between their atoms in both solid and liquid states.

Melting and boiling points of group 14 elements are much higher than group 13 elements.

When moving down the group, the melting and boiling points decreases.

Melting and boiling points of crbon solicon group

Group 15 elements melting and boiling points

  1. Nitrogen has the lowest melting point and boiling point.
  2. Antimony has the highest melting point and boiling point.
Group 15 elements melting and boiling points

Group 16 elements melting and boiling points

  1. Oxygen has the lowest melting point and boiling point.
  2. Tellurium(Te) has the highest melting point and boiling point.
Group 16 elements melting and boiling points

Boiling points of group 17

Boiling points increases on moving down from F to I

boiling points of halogen elements

Melting and boiling points of 3d metals

Melting and boiling points of 3d metals are generally higher than s block elements.

Vanadium has the highest melting point and zinc has the lowest melting point.

But melting and boiling points do not show regular trends.

Melting and boiling points of 3d metals

Why zinc has the lowest melting point in 3d metals?

Zinc has a stable electrons configuration, 3d10 4s2. Therefore Zn does not contribute more electrons to the metallic lattice like other 3d metals. Hence strength of metallic lattice is less than other 3d metals lattices. So Zn has the lowest melting point in 3d metals.


Melting point drop of manganese

Manganese electrons configuration is 3d5 4s2. That electrons configuration has some stability. So contributing electrons to the lattice is limited in Mn. Therefore lattice is not much strong. That is the reason why Mn has a drop in melting point.



Melting and boiling points of compounds


Melting and boiling points of alkali metal halides

Melting and boiling points of alkali metal halides decreases with the increase in atomic mass of the halides as:
F- > Cl- > Br- > I-
Ex: Melting point of NaCl is higher than NaBr

For given halide ion, melting and boiling points of LiX is always less than NaX.




Melting and boiling points of organic compounds

Thousands of organic compounds are discovered so far by scientists in the world. With discovering lot of compounds, organic chemistry was born. In this chapter we are going to discuss melting and boiling points of organic compounds.

Melting and boiling points of organic compounds

Following facts are important when we studying melting and boiling point values of organic compounds.

  • Relative Molecular mass
  • Dipole dipole interactions
  • Ability of making hydrogen bonds
  • Structure of carbon chain

Melting and boiling points of alkanes, alkenes, alkynes

  • Alkanes are non polar molecules. There are only Van der Waals forces between alkane molecules. When relative molecular mass increases in alkane compounds, melting and boiling points values are also increased.
    melting and boiling points of alkanes

  • Melting and boiling points increases alkane, alkene, alkyne respectively.

Consider ethane, ethene, ethyne

ethyne (alkyne compound) has the highest melting and boiling point.

melting and boiling points of alkanes, alkenes, alkynes

When number of hydrogen bonds and strength of hydrogen bonds increases, melting and boiling points increases.


Alcohols, aldehyde, ketone and carboxylic acids

  • All of alcohols and carboxylic acids can form hydrogen bonds.
  • Carboxylic acids forms most strong and highest number of hydrogen bonds among them.
  • So, carboxylic acids has highest melting and boiling points.
  • Dipole dipole interactions between aldehydes and ketones molecules are less strong than hydrogen bonds in alcohols.
  • Therefore melting and boiling points of alcohols are higher than aldehydes and ketones.
melting and boiling points of alkanes aldehydes ketones alcohols carboxylic acids

Melting and boiling points of alkyl halide compounds

Halogen atom is more electro negative than carbon atom. So C-X bond is polarized. There are dipole dipole interaction between alkyl halide compounds. These interactions are much stronger than intermolecular forces between alkanes,

Melting and boiling points of alkyl halide compounds are much higher than alkanes.

melting and boiling points of alkanes alkyl halides aldehydes ketones alcohols carboxylic acids.jpg

When relative molecular mass of organic compound increases, melting and boiling points also increase.



Now we discuss some problems by comparing different elements and compounds which have different melting and boiling points. These problems very important in examinations. Study them carefully.



Why d block elements have higher melting points than s block elements?

d block elements can contribute more electrons to the metallic lattice. As an example vanadium can contribute 5 electrons.

But s block elements can only contribute one or two electrons. Alkali metals can one electron and alkali earth metals can two electrons.

Contributing more electrons to the metallic lattice will increase the strength of metallic bonds.

Due to more strong metallic bonds, d block elements have higher melting values.



Why H2S having less boiling point than H2O

H2S boiling point: -600C

H2O boiling point: 1000C

  • At room temperature, hydrogen disulfide (H2S) is a gas. But water (H2O) is a liquid. That says us H2S has the less boiling point.
  • H2S and H2O are bent shape molecules.
  • O and S are group VIA elements.
  • Molecular mass of H2S = 34 and molecular mass of H2O = 18. Molecular mass of H2S is greater than H2O.
  • But, There are strong hydrogen bonds between H2O molecules. H2S molecules have only weak dipole dipole interactions.

Hydrogen bonds in H2O

hydrogen bonds in H2O

  • Due to existence of strong hydrogen bonds in H2O molecules, H2O has high boiling point than H2S , though H2S has greater molecular mass.


Which metal has the highest melting point?

Tungsten (W). From metals, tungsten has the highest melting point in periodic table. It is located in d block. 3,422 0C is the melting point of tungsten.



Which s block metal has the highest melting point?

Beryllium has the highest melting point from s block metals. It is about 1,287 0C



Lowest melting point from metal elements

Mercury (Hg) has the lowest melting point (-38.83 0C) because mercury has a very weak metallic lattice.



Which element has the lowest melting point element in periodic table

Helium (He) is the element which has lowest melting point (-272.2 0C). Helium exist as atoms. It does not form compounds and no intermolecular force between He atoms. Also relative molecular mass (1) is very low.



Still have a question? Ask it now from us and find the answer.

What can understand by melting and boiling points of elements in periodic table?

We know, elements in periodic table are in solid state, liquid state and gaseous state. Intermolecular forces, relative molecular mass are factors which decides melting and boiling point of element.

Let's consider two metals. One metal has very high melting point than other one. In metals, metallic lattice is the major factor of deciding melting and boiling point. More strong metallic lattice have higher melting point.

We can understand about elements' intermolecular forces, relative molecular masses from studying melting and boiling points.



Why different elements have different melting points?

Melting point depends on their molecular mass and intermolecular forces between elements or molecules. Different elements have different molecular mass and intermolecular forces. So their melting point values are different from other elemets and compounds.



Why group ii elements melting at higher temperatures than group i elements?

Metallic lattices of group ii metals are much stronger than group i metals because group ii elements give two electrons to the lattice. Therefore, group i metals melt at higher temperatures.



Melting point of Mg is in s block?

Metallic lattice of magnesium is much strong than sodium. So melting point of Mg is higher than Na.



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