Melting and Boiling Points of Elements of Periodic Table

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

In this tutorial, we will cover following sections.

• Reasons for having different melting and boiling points of elements and compounds
• Comparing melting and boiling points values of each group in periodic table with trends
• Melting and boiling points of organic compounds
• Comparing melting and boiling points of different elements and compounds in s, p and d blocks

Melting and boiling points of elements

Melting and boiling point variations are not clear (do not have uniform pattern) throughout the periodic table (this means we cannot see similar trend always. You will understand this when you finish reading this tutorial).

But we can see, some elements have higher melting points and boiling points while some elements have less. In first part of this tutorial, we learn melting and boiling points of s, p, d blocks elements and their compounds and followed by organic compounds.

IVA^th group elements (carbon and silicon) show high melting and boiling points in second and third periods respectively because they have covalent gigantic lattice structures.

Melting and boiling points across a period

In first three periods, there is a clear variation of melting and boiling points (has a clear trend). Melting and boiling points increase upto the IVA group with when going from left to the right. (As an example from sodium to argon in third period). IVA group has the highest melting and boiling point element. Then it starts to decrease melting and boiling points from VA group to noble gases (VIIIA).

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

There are many reasons to effect for melting and boiling points of elements and compounds. One or several of things may effect to melting and boiling points.

1. Molecular mass - when molecular mass increase, possibility of increasing melting and boiling point is also high.
2. Intermolecular forces such as hydrogen bonds, dipole - dipole attraction forces, van der waals' forces between atoms or molecules. When intermolecular forces become stronger, it also increases the melting and boiling points of elements and compounds.
3. Metallic lattice ( important to decide melting points of metals such as sodium, magnesium and other metal elements)
4. Ionic lattice - In ionic compounds such as NaCl, CaF₂, MgO, ionic lattice exist. According to the strength of ionic lattice, melting and boiling points may vary.

Lowest melting and boiling points elements in a period

Inert gasses have the lowest melting and boiling points element in period because their form only van der waals' forces are they are very weak to form a strong intermolecular force between atoms.

Trends of melting and boiling points groups of periodic table

Now, we are going to learn about, how melting and boiling points of elements vary in group by considering taking each group separately.

Melting and boiling points values of s block

S block contains group IA and group IIA and most elements of they are metals without hydrogen. (hydrogen has both alkali metal properties and halogen properties.)

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 lithium to cesium.

Hydrogen

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

Melting and boiling points of alkaline earth metals

Alkaline earth metals (Be, Mg, Ca, Sr, Ba, Ra) have low melting and boiling points when compared with d block metals. 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 in alkali earth metal group.

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.

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

Why beryllium have high melting point and boiling point than other member of group two?

Beryllium is the smallest size atom of the group 2 elements. So its ionic lattice is more stronger than other alkaline earth metals.

Melting and boiling point of p block elements

Now we are going to discuss about variations of melting and boiling points of p block elements.

In the p block, there are varies types of elements including metals, non-metals and their physical states are also very different. At room temperature, some of they are in solid state, and some are at gaseous state. Bromine is at liquid state too.

P block contains the highest melting points element (carbon) and lowest melting point element of the periodic table (helium).

Now, we are going to look melting and boiling points of p block elements from group 13 to group 18.

Halogen and inert gases melting and boiling points

Halogen and noble gases are located in p block of the periodic table. Halogens exist as diatomic molecules such as F₂, Cl₂, Br₂, I₂ and noble gases exist as monoatomic molecules.

When going down the each group, molecular mass increases which can be reason to have a higher melting and boiling points. Also, all halogen and inert gas molecules form only van der waals' forces which are weakest intermolecular forces and does not effect much to melting and boiling of halogen and noble gases. Molecular mass of molecules have the greatest effect to increment of melting and boiling points. So Melting and boiling points of both halogen and inert gases increase along the group.

Boiling and melting points of group 13 elements

Boron, Aluminum, Gallium, Indium, Thallium 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 boiling points. Gallium has very low melting point (303K).

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.

Carbon (diamond as a allotrope of carbon) has the highest melting point and boiling point between group 14 elements.

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 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.

Boiling points of group 17

Boiling points increases on moving down from fluorine to iodine.

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.

Why zinc has the lowest melting point in 3d metal series?

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

Melting point drop of manganese

Electrons configuration of manganese is 3d⁵ 4s². That electrons configuration has some stability because all five d orbits are half filled (each d orbit has one electron.) So contribution of electrons to the metallic lattice is limited in manganese. Therefore lattice is not much strong. That is the reason why manganese has a sudden drop in melting point.

Melting and boiling points of compounds

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.

Boiling points of ethane (alkane) and ethanoic acid (carboxylic acid) is listed below and they are two different types of organic compounds.

• Methane (CH₄): -161.5⁰C
• Ethanoic acid (CH₃COOH): 118.1⁰C

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 increases alkane, alkene, alkyne respectively.

Consider ethane, ethene, ethyne

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

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 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.

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.

Is p block metals melting points are higher than s block?

First we will look, what are the p block metals and what are the s block metals. You know when we discuss about melting points of metals, their metallic lattice is so important. So now you know what should we find out to compare melting points of p block metals and s block metals.

When metallic lattice of a metal is strong, that metal has a great chance to has a higher melting point.

As examples, two metals, sodium and aluminium are taken to compare. Sodium is s block metal and aluminium is a p block metal. But both are located in 3rd period of the periodic table.

Due to release of three electrons and less radius, metallic lattice of aluminium is much stronger than sodium. So melting point of aluminium is greater than sodium.

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

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

which atom has the highest melting/boiling point between Cs and W?

Tungsten (W) has the highest melting point of all metals. Caesium (Cs) is a soft metal which has a very low melting point (28⁰C).

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

boiling and melting points of 1a group order

Li > Na > K > Rb > Cs > Fr > H

Lithium has the highest melting and boiling point while hydrogen has the lowest in IA group. Hydrogen exists as a gas at room temperature and francium is a liquid at room temperature. All other group IA materials are solids at room temperature.

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.

Which of the following compounds has the highest boiling point?

Methane (CH₄), Ethane (CH₃CH₃), Ethanol (CH₃CH₂OH), Borane (BH₃), Hydrogen sulfide (H₂S)

Answer: Molecular mass and strength of secondary bonds are the key facts of deciding boiling point of compounds.

• From secondary bonds, hydrogen bonds are the most strong bonds and molecules with hydrogen bonds show higher boiling point.
• When, molecular mass of molecule is also increased, boiling point increases too.

From above two facts, only ethanol can make hydrogen bonds and ethanol has the highest moledular mass too. Therefore, ethanol has the highest boiling point from given compound series.

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.

What are some melting points and boiling points of some flammable gases?

We can list several flammable gases and their melting and boiling points of them.

Alkanes are easily flammable. As an example, consider methane. Methane's melting and boiling points are -182.4⁰C and -161.5⁰C respectively.

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.

boiling and melting points which depend on what factors?

According to the element or compound type, melting and boiling point depend. This is explained below.

• If we consider metals, their melting and boiling point depend on their metallic lattice. If their metallic lattice is strong, melting and boiling point depend increases.
• When we come to molecules such as oxygen, water, noble gases, their melting and boiling point depend on their molecular mass and intermolecular forces.
• Melting and boiling points of ionic compounds like sodium chloride depend on their ionic lattice.

Why group IIA elements melting at higher temperatures than group IA 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.

why boiling point of calcium is greater than potassium?

Lattice strength of calcium is greater than potassium due to two reasons.

1. Radius of calcium is smaller than potassium.
2. calcium can give two electrons to the metallic lattice while potassium can only give one electron.

Due to these two reasons, metallic lattice of calcium is much greater than potassium.

what has a melting point of -219⁰C and a a boiling point of -183⁰C ?

Oxygen (O₂)

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 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.

what happens to melting point in s block

If you study s block elements in same period, you will see alkaline earth metal (group 2) has a higher melting point than alkali metal (group 1) because lattice strength of alkaline earth metal element is stronger than alkali metal element.

why do some elements have a high melting point?

When some elements are greater in some properties, they have a high melting point.

As examples, we can consider metals. When we talk about metals, metallic lattice is a must to understand. When metallic lattice is strong, that metal has a higher melting point. Metallic lattice of sodium is weak than magnesium. Therefore, magnesium has a high melting point than sodium.

As another example, water and hydrogen sulfide are taken. Water forms hydroggen bonds which are the strongest inter molecular forces type. But hydrogen sulfide cannot form hydrogen bonds. So, water has a higher melting point and also a boiling point too.

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