Trends of Periodic Properties in Periodic Table

Moseley gave the Modern Periodic law which states that “Physical and chemical properties of the elements are periodic functions of their atomic numbers”. In modern periodic table elements have been arranged according to their atomic numbers and as stated above atomic numbers are directly related to their physical and chemical properties. That’s why elements show periodicity in their physical and chemical properties in the periodic table. For example, as we move from left to right in a period, atomic size decreases. Although we find some exceptions which do not follow these periodic table trends. Recurrence of similar electronic configuration in the periodic table is the cause behind periodicity. Thus, we can say that elements having similar electronic configuration have similar properties. Periodic trends provide chemists a quick and easy tool to quickly predict properties of elements. In this article we will discuss periodic properties and their trends in the periodic table in detail.


Periodic Trends of Properties of Elements In Periodic Table 

Modern periodic law is the base of periodic trends of properties of elements in the modern periodic table. Following properties of elements show a very clear periodic trends in periodic table –

  • Atomic Radius 

  • Ionization energy 

  • Electron affinity 

  • Electronegativity 

  • Valence electrons 

  • Valency 

  • Metallic character of the elements 

  • Non – metallic character of the elements 

  • Reactivity of elements 

  • Melting and boiling points of elements 


Atomic Radius 

Atomic radius is the distance between the center of the nucleus of an atom to its outermost shell. 

Periodic trend of atomic radius across a period – As we move from left to right in a period, atomic radius gradually decreases.

Reason – As we move left to right in a period atomic number of the elements increases so nuclear charge increases while number of shells in elements remain the same. 

Example – 

Elements of 2nd period 

Li

Be

B

Atomic Number 

3

4

5

Nuclear Charge or Number of Protons In The Nucleus 

3

4

5

Number of Shells 

2

2

2

Atomic Radius (In Pm)

152

106

88


Exceptional Behavior – Noble gases show exceptional behavior. The atomic radii of inter gases suddenly increase as compared to its predecessor halogen atom. The reason for this type of exceptional behavior is that atomic radius refers to van der Waal’s radius in case of noble gases while in case of other elements it refers to covalent radius. 

Across a Group – on moving top to bottom in a group, atomic radii gradually increase as nuclear charge and number of shells also increase. 


Ionization Energy 

Ionization energy is the amount of energy required to remove one electron from an atom. First ionization energy is the amount of energy required to remove one outermost electron from an atom. 

Periodic trend of ionization energy across a period – As we move from left to right in a period, ionization energy gradually increases.

Reason – As we move left to right in a period atomic size or atomic radius decreases while nuclear charge increases. 

Example - 

Elements of 3rd period 

Al

Si

P

Atomic Number 

13

14

15

Nuclear Charge or Number of Protons In The Nucleus 

12

14

15

Number of Shells 

3

3

3

First Ionization Energy 

577.5

786.5

1011.8


Exceptional Behavior – Beryllium possesses more first ionization energy than Boron. Because beryllium has half - filled s – orbital and more energy is required to remove an electron from half or completely filled orbitals. That is why noble gases also show exceptionally high ionization energies. 

Across a Group – on moving top to bottom in a group, ionization energy gradually decreases as atomic radius increases.


Electron Affinity 

The amount of energy required to add an electron to an atom is called electron affinity of that atom. In other words, electron affinity is the change in energy when an electron is added to the atom and a neutral atom changes into a negative ion. 

Periodic trend of electron affinity across a period – As we move from left to right in a period, electron affinity gradually increases.

Reason – As we move left to right in a period atomic size or atomic radius decreases while nuclear charge increases. 

Elements of 4th period 

Ti

V

Cr

Atomic Number 

22

23

24

Nuclear Charge or Number of Protons In The Nucleus 

22

23

24

Electron Affinity (Ev) 

0.075

0.527

0.675


Exceptional Behavior – Beryllium does not form a stable anion, so it releases less energy than boron on adding an electron. While nitrogen neither releases nor requires a significant amount of energy on adding an electron so it has electron affinity almost equal to zero. 

Across a Group – on moving top to bottom in a group, electron affinity gradually decreases. 

Electronegativity 

Electronegativity is a measure of the ability of an atom or molecule to attract pairs of electrons in the context of a chemical bond. 

Across A Period – As we move left to right across a period, electronegativity increases in the periodic table. Fluorine is the most electronegative element. 

Reason – As the nuclear charge increases of an atom, its electron loving character also increases. 

Example –

Elements of 3rd period 

Na

Mg

Al

Atomic Number 

11

12

13

Nuclear Charge or Number of Protons In The Nucleus 

11

12

13

Electronegativity (Pauling Scale)

0.93

1.31

1.61


Across A Group – As we move top to bottom in a group, electronegativity decreases. 


Valence Electrons 

Electrons present in the outermost shell of an atom are called valence electrons of that atom. 

Across A Period – As we move left to right across a period in the periodic table, the number of valence electrons increases.

Example –

Elements of 3rd period 

Na

Mg

Al

Atomic Number 

11

12

13

Electronic Configuration 

2,8,1

2,8,2

2,8,3

Valence Electrons 

1

2

3


Across A Group – Across a group, valence electrons remain constant. It means elements present in the same group have the same number of valence electrons. For example, hydrogen, lithium, and sodium elements are present in the 1st group and have the same number of valence electrons which is one. 


Valency 

Valency is the combining capacity of an atom.

Across a Period – on moving left to right across a period in the periodic table, first valency increases then decreases. 

Example –

Elements of 2nd period 

Li

Be

B

C

N

o

F

Ne

Atomic Number 

3

4

5

6

7

8

9

10

Electronic Configuration 

2,1

2,2

2,3

2,4

2,5

2,6

2,7

2,8

Valency

1

2

3

4

3

2

1

0


Across A Group – There is no change in valency across a group. Elements of the same groups show the same valency.


Metallic Character of The Elements 

Across a Period – As we move left to right across a period in the periodic table, metallic character of elements decreases. 

Example –

Elements of 2nd period 

Li

Be

B

C

N

o

F

Ne

Metallic Character

Metal

Metal

Metalloid

Nonmetal

Nonmetal

Nonmetal

Nonmetal

Nonmetal


Across a Group – As we move top to bottom in a group of the periodic table, the metallic character of elements increases. 


Non - Metallic Character of The Elements 

Across a Period – As we move left to right across a period in the periodic table, nonmetallic character of elements increases. 

Example

Elements of 2nd period 

Li

Be

B

C

N

o

F

Ne

Nonmetallic Character

Metal

Metal

Metalloid

Nonmetal

Nonmetal

Nonmetal

Nonmetal

Nonmetal


Across a Group – As we move top to bottom in a group of periodic table non metallic character decreases.

Example -

Group 15

Nonmetallic Character 

N

Nonmetal 

P

Nonmetal 

As

Metalloid 

Sb

Metalloid 

Bi

Metal 


Reactivity of Elements 

Reactivity of metals depends on its electropositive character. So, more is the metallic character, more is the electropositive nature of the element and more is its reactivity. As metallic character decreases across a period left to right, so reactivity also decreases. Although reactivity of nonmetals increases on moving left to right across a period. Thus, we can conclude, as we move left to right in a period, the reactivity of elements gradually decreases up to the group thirteen and then starts increasing. 

Elements of 3rd period 

Na

Mg

Al

Si

P

S

Cl

Ar

Group 

1

2

13

14

15

16

17

18

Reactivity 

Very reactive 

Reactive 

Reactive 

Least reactive 

Reactive 

Reactive 

Very reactive 

Inert 


Reactivity decreases 🡪


Reactivity increases🡪



Melting And Boiling Points of Elements 

Melting and boiling points of metals decrease gradually from top to bottom in a group. While melting and boiling points of nonmetals increase on moving from top to bottom in a group of the periodic table.  

This ends our coverage on the topic “Trends of Periodic Properties in the Periodic Table”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic. If you are looking for solutions of NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.