Periodic Table: Periodic Properties, Trends & Classification
Study modern periodic table, periodic properties, atomic radius, ionization energy, electronegativity, electron affinity and periodic trends for JEE Main Chemistry.
The central idea of this chapter
Elements show periodic variation in properties based on electronic configuration. This chapter connects atomic structure with chemical behaviour through periodic trends.
What should you understand first?
The periodic table is a backbone of inorganic chemistry. Master periodic trends and their exceptions. This chapter links atomic structure with chemical properties.
Core concepts
- Periodic law f(Z)
- Atomic radius โ across, โ down
- Ionization energy โ across, โ down
- Electronegativity F = 4.0
- Electron affinity Cl releases more energy than F
Useful building blocks
- Effective nuclear charge Zeff = Z โ ฯ
- Screening effect ฯ = shielding
- Ionic radius Cations < Anions
- Isoelectronic same electrons
- Diagonal relationship Li-Mg, Be-Al
Periodic Table formula sheet
Understand periodic trends with their underlying reasons. Apply effective nuclear charge, shielding and electronic configuration concepts to explain variations in periodic properties.
| Topic | Formula / Relation | Meaning or use |
|---|---|---|
| Modern periodic law | Properties = f(Z) | Properties of elements are periodic functions of atomic number |
| Effective nuclear charge | Zeff = Z โ ฯ | Net attractive charge experienced by an electron |
| Atomic radius trend | Decreases across period, increases down group | Effective nuclear charge increases across a period, while new shells are added down a group |
| Ionic radius | Cation < Neutral atom < Anion | Cations are generally smaller and anions larger than their parent atoms |
| Isoelectronic series | Size โ 1/Z | For species having the same number of electrons, size decreases as nuclear charge increases |
| Ionization energy | IEโ < IEโ < IEโ | Successive ionization energies generally increase |
| IE trend | Increases across period, decreases down group | Important exceptions include Be > B and N > O |
| Electron affinity / electron gain enthalpy | EAโ is generally exothermic; EAโ is endothermic | Adding a second electron to an already negatively charged ion requires energy |
| Electron affinity trend | Generally becomes more favorable across a period, with important exceptions | Chlorine has a more favorable electron gain enthalpy than fluorine because of fluorine's very small size; important exceptions exist |
| Electronegativity | F > O > Cl > N | Relative electronegativity order on the Pauling scale |
| EN trend | Increases across period, decreases down group | Fluorine is the most electronegative element |
| Mulliken electronegativity | ฯ = (IE + EA) / 2 | Electronegativity estimated from ionization energy and electron affinity |
| Metallic character | Decreases โ , Increases โ | Opposite to non-metallic |
| Oxidation state | Commonly related to group number for representative elements | For representative elements |
How to approach Periodic Table problems
First identify property (radius, IE, EN, EA), then apply periodic trend with exceptions. Use Zeff concept for explaining order of properties.
Size & energy trends
- Atomic size? โ โ , โ โ
- Ionic size? Cation < Anion
- IE order? โ โ , โ โ
- EA order? Cl > F > Br
- Stable config? Half/full filled
Electronegativity & character
- EN order? F > O > Cl > N
- Metallic? โ โ , โ โ
- Oxidation state? Group no
- Diagonal? Li-Mg, Be-Al
- Isoelectronic? Size โ 1/Z
How to prepare Periodic Table
Start with modern periodic law and table structure, then master all periodic trends with exceptions. Focus on IE, EN and EA order questions.
What to do
- Learn periodic table structure (groups, periods, blocks)
- Master atomic and ionic radius trends
- Understand ionization energy with exceptions
- Practise electronegativity and electron affinity orders
- Revise diagonal relationship and isoelectronic species
Common mistakes
- Forgetting IE exceptions (Be > B, N > O)
- Confusing EA order (Cl > F due to small size of F)
- Wrong ionic radius comparison (cation < neutral < anion)
- Mixing up metallic and non-metallic trends
- Forgetting stable configurations (half/full filled)
Ready to test Periodic Table?
Revise the formula sheet, then solve mixed JEE Main problems on periodic properties, trends and electronic configuration.
Periodic Table FAQ
Short answers to frequently tested ideas in this chapter.
Modern periodic law states that properties of elements are periodic function of their atomic numbers. Elements are arranged in order of increasing Z.
Ionization energy is minimum energy required to remove outermost electron from isolated gaseous atom. It increases across period and decreases down group.
Electronegativity is tendency of atom to attract bonded electrons. Fluorine is most electronegative element (4.0 on Pauling scale).