Physical and chemical properties of elements

Introduction to the Physical and Chemical Properties of Elements in Chemistry

Atomic and molecular structure, chemical bonding and synthesis, and properties of substances are basic to the subject of contemporary chemistry giving students an insight into the nature of the elements that make up our surroundings. Physical characteristics include mass density, state at room temperature, and other factors that determine the attributes of an element under the stated conditions of pressure and temperature like melting point, boiling point and electrical conductivity. These properties are vital in describing the forms of matter and the changes in between, in analyzing the stabilities of materials and uses for them.
Chemical properties, on the other hand, go further in explaining how the elements will endorse each other to formulate compounds and molecules. It deals with their activity, acidity or alkalinity, and potential to form new materials with differing characteristics through the action of combining with other elements. For instance, alkali metals react with water and oxygen readily or with ease and noble gases do not readily react with other elements because their electron orbit is complete. These chemical properties enable scientists to predict the reaction, develop synthetic routes and fine-tune several industrial processes including the synthesis of drugs, materials and treatments of pollutants.

Combined, the study of both physical and chemical characteristics not only proves extremely beneficial in comprehending the compositions’ innate qualities but also provides the knowledge needed to create uses for the numerous benefits that these elements offer. Advances in the knowledge of element properties have enabled the invention of new materials with desired characteristics and the understanding of biological systems’ workings among other areas of applications.

In this article, we will be focussing on the in-depth knowledge of the important topic of physical and chemical properties of the elements, which is the sub-topic of the chapter Classification of Elements and Periodic Table from class 11 chemistry. It is not only essential for board exams but also for competitive exams like the Joint Entrance Examination (JEE Main), National Eligibility Entrance Test (NEET), and other entrance exams such as SRMJEE, BITSAT, WBJEE, BCECE, and more. Over the last ten years of the JEE exam (from 2013 to 2023).

Let's discuss Element's physical and chemical properties in detail to gain some insight in a joyful manner to solve some related problems on the same.

Exploring Physical and Chemical Properties

There are various factors on which the physical and chemical properties of the elements depend, let us discuss each point in detail.

Atomic Volume

In moving from left to right in a period the atomic volume first decreases and then increases because of the following reasons:

• As we move in a period from left to right, first the increase in nuclear charge overcomes the increase in the number of electrons. Thus, the atomic volume decreases.

• But on moving further in a period, newly added electrons enter into the p orbitals and because of the high shielding power of s and p orbitals, atomic volume increases.

In moving from top to bottom in a group, the atomic volume increases due to the increase in the number of shells.

Reccommende topic video on ( Physical and Chemical Properties of elements)

Solved Examples Based On- Atomic Volume

Example 1: The atomic radius of elements of which of these would be nearly the same?

1) Na, K, Rb, Cs

2) F, Cl, Br, I

3) Li, Be, B, C

4) (correct) Fe, Co, Ni, Cu

Solution: As we have learned, the Physical Properties of Elements - Atomic radii of transition elements remain almost the same in the period. Therefore, Fe, Co, Ni, and Cu have nearly the same atomic radii.

Hence, the answer is the option (4).

Density

The density of elements also follows almost the same order as the atomic volume. In moving from left to right in a period, the density increases first and becomes maximum till some middle elements thereafter it starts decreasing gradually.

Example 2: Among the following which has the maximum density?

1) Phosphorous

2) Sulphur

3) Silicon

4) (correct) Aluminium

Solution: Density

Value of density(in g/cm³) of given elements:-

1) Phosphorous - 1.823
2) Sulphur - 2.06
3) Silicon - 2.34
4) Aluminium - 2.70

2.70 is greater than others, so Al has the maximum density among given elements.

Hence, the answer is the option (4).

Example 3:Which of the following has the maximum density?

1) Sulphur

2) Phosphorus

3) (correct) Aluminium

4) Silicon

Solution: Properties of Elements -

Density, Metals have a higher density than metalloids and metalloids have a higher density than non-metals.

Hence, the answer is the option (3).

Example 4: Which of the following is arranged in order of increasing density?

1) Al < Mg < C(graphite) <B

2) Al > Mg > C(graphite) >B

3) (correct) Mg < C(graphite) <B <Al

4) Mg > C(graphite) > B > Al

Solution: Physical Properties of Elements -Density Density increases from left to right up to the middle in a period and increases down the group in the periodic table. Graphite is a less dense form of carbon thus the order of density is:

Mg < C(graphite) <B <Al

Hence, the answer is the option (3).

Melting Points and Boiling Points

The melting points of elements show a general trend with their atomic numbers. The elements with low atomic numbers have high melting points while the elements with higher atomic numbers have low melting points. In a period from left to right, the melting points of elements first increase and become maximum till some middle elements and then it decreases gradually.

Value of melting point of elements-

The boiling points of elements also show similar trends as the melting points but the trend is not that much regular.

In moving down the group, melting and boiling points follow the regular trend but the trend is different for different groups. For example for the alkali group, the melting and boiling points decrease in moving from top to bottom but for halogens, the melting and boiling points increase in moving down the group.

Example 6:Which of the following has the lowest melting point?

1) Mg

2) Be

3) Ca

4) (correct) Sr

Solution: The melting point of elements shows a general trend with their atomic numbers. The elements with low atomic numbers have high melting points while the elements with higher atomic numbers have low melting points. In a period from left to right, the melting points of elements first increase and become maximum till some middle. The melting point of elements decreases down the group because in moving down the group, the size of elements increases, and thus the metallic bond between the atoms becomes weaker, and hence the melting point decreases.

Hence, the answer is the option (4).

Example 7:What happens to the conductivity of metal when temperature is increased?

1) (correct) It decreases

2) Remains constant

3) It increases

4) None of these

Solution: As we have learned, the Effect of temperature on conductivity -

The conductivity of the metal decreases with the temperature rise. This is because with the temperature rise the positively charged kernels also, start vibrating which interferes with the movement of electrons.

As the temperature increases the molecular vibration also increases which obstructs the flow of free electrons, thus conductance decreases.

Hence, the answer is the option (1).

Example 8 The reason for good thermal conductance of metal is:

1) Transport of energy

2) (correct) Free electrons and frequent collision of atoms

3) Lattice defects

4) Capacity to absorb energy

Solution: As we have learned Thermal conductivity of metals - On heating a part of the metal, the kinetic energy of the electron in that region increases. The energised electron moves rapidly to the cooler part and gives its excess kinetic energy to other electrons in the cooler part of the metal. Thus heat is conducted through metal.

For good conductors, there must be free electrons present in the metal.

Hence, the answer is the option (4).

Conclusion

The general concept of physical and chemical properties of elements in chemistry helps to define the relations of the matters in the world we live in. Such properties offer essential information concerning the aspects of elements that would be appropriate for use within different states and conditions, particularly in manufacturing industries, including metallurgical and electronics. Knowledge of properties like electrical and thermal conductivity, melting point, and density is useful not only in the design of new materials but also in the improvement of the control of substances for the development of technologies.

Likewise, chemical characteristics explain the interaction of elements in reactions and help in the creation of new chemical compounds and products. The chemical properties of elements that allow them to make bonds, their reactivity, and the use of elements and compounds in biochemical processes reveal the mechanisms of interaction between chemical compounds and their utilization in the given environment. For instance, the ability of transition metals to be so reactive means that catalysts for industrial purposes need to be included, while the fact that halogens react readily to form acids is influencing environmental chemistry and the synthesis of drugs.

By studying physical and chemical characteristics, students learn general laws that regulate elements’ actions. Much of what we know, enables us to find new applications across all fields from renewable energy, to new medications. As scientific knowledge progresses in contemporary society, the noble collaboration between gaining the properties of elements and using this information holds the ability to dictate future discoveries and foster mankind’s perception of the universe’s basics.