This MCQ module is based on: Nomenclature Electronic Configuration
TOPIC 10 OF 28
Nomenclature Electronic Configuration
🎓 Class 11
Chemistry
CBSE
Theory
Ch 3 – Classification of Elements and Periodicity in Properties
⏱ ~14 min
🌐 Language: [gtranslate]
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Nomenclature and Electronic Configuration of Elements
3.4 Nomenclature of Elements with Atomic Number > 100
The naming of new elements had been traditionally the privilege of the discoverer (or discoverers) and the suggested name was ratified by the IUPAC. In recent years this has led to some controversy. The new elements with very high atomic numbers are so unstable that only minute quantities, sometimes only a few atoms of them are obtained. Their synthesis and characterisation, therefore, require highly sophisticated costly equipment and laboratory.
Such work is carried out with competitive spirit only in some laboratories in the world. Scientists, before collecting reliable data on the new element, at times get tempted to claim for its discovery. For example, both an American group and a Russian group claimed credit for discovering element 104. The Americans named it Rutherfordium, whereas the Russians named it Kurchatovium. To avoid such problems, IUPAC has made a recommendation that until a new element's discovery is proved, and its name is officially recognised, a systematic nomenclature derived directly from the atomic number using the numerical roots be used.
IUPAC Naming Rules
| Digit | Latin/Greek root | Abbreviation |
|---|---|---|
| 0 | nil | n |
| 1 | un | u |
| 2 | bi | b |
| 3 | tri | t |
| 4 | quad | q |
| 5 | pent | p |
| 6 | hex | h |
| 7 | sept | s |
| 8 | oct | o |
| 9 | enn | e |
Steps to derive name:
- Write the atomic number in digits (e.g., 105 → 1, 0, 5)
- Replace each digit with its root (un, nil, pent)
- Combine and add suffix "-ium" → Unnilpentium
- Symbol: first letter of each root → Unp
Examples of Systematic Naming
| Atomic Number | IUPAC Name | IUPAC Symbol | Permanent Name (later) |
|---|---|---|---|
| 101 | Unnilunium | Unu | Mendelevium (Md) |
| 104 | Unnilquadium | Unq | Rutherfordium (Rf) |
| 105 | Unnilpentium | Unp | Dubnium (Db) |
| 110 | Ununnilium | Uun | Darmstadtium (Ds) |
| 118 | Ununoctium | Uuo | Oganesson (Og) |
| 120 | Unbinilium | Ubn | (not yet discovered) |
🎯 Interactive: IUPAC Name Generator
Enter any atomic number (101–130) to see its systematic IUPAC name and symbol.
IUPAC Name: Ununpentium
IUPAC Symbol: Uup
3.5 Electronic Configurations of Elements & the Periodic Table
In the Modern Periodic Table, elements are arranged according to increasing atomic number. This arrangement also reflects the systematic filling of orbitals by electrons, governed by the Aufbau principle, Pauli's exclusion principle, and Hund's rule.
The Periodic Table can be divided into four blocks based on the orbital being filled:
3.5.1 s-Block Elements (Groups 1 and 2)
The s-Block elements have the general outer electronic configuration ns¹ (Group 1, alkali metals) and ns² (Group 2, alkaline earth metals).
- Group 1: Li, Na, K, Rb, Cs, Fr — Alkali metals
- Group 2: Be, Mg, Ca, Sr, Ba, Ra — Alkaline earth metals
- Properties: Soft metals, low melting points, very reactive (especially with water), form ionic compounds, lose electrons readily, low ionisation enthalpy.
3.5.2 p-Block Elements (Groups 13–18)
The p-Block elements have the outer electronic configuration ns²np¹ to ns²np⁶. The p-block together with the s-block constitute the representative elements (or main group elements).
- Group 13: B, Al, Ga, In, Tl — ns²np¹
- Group 14: C, Si, Ge, Sn, Pb — ns²np²
- Group 15: N, P, As, Sb, Bi — ns²np³
- Group 16: O, S, Se, Te, Po — ns²np⁴ (chalcogens)
- Group 17: F, Cl, Br, I, At — ns²np⁵ (halogens)
- Group 18: He, Ne, Ar, Kr, Xe, Rn — ns²np⁶ (noble gases)
Special note on Helium: Although He has 1s² (s-block configuration), it is placed in Group 18 with noble gases because its chemistry resembles them — fully filled shell, chemically inert.
3.5.3 d-Block Elements (Groups 3–12)
The d-Block elements (also called transition elements) have the general outer electronic configuration (n−1)d¹⁻¹⁰ ns⁰⁻².
- 4 series: 3d (period 4: Sc–Zn), 4d (period 5: Y–Cd), 5d (period 6: La, Hf–Hg), 6d (period 7: Ac, Rf–Cn)
- Properties: Hard, high melting/boiling points, variable oxidation states, coloured compounds, paramagnetic, catalytic activity.
3.5.4 f-Block Elements (Inner Transition)
The f-Block elements have the general outer electronic configuration (n−2)f¹⁻¹⁴ (n−1)d⁰⁻¹ ns²:
- Lanthanoids (4f series): Ce (Z=58) to Lu (Z=71) — placed below period 6.
- Actinoids (5f series): Th (Z=90) to Lr (Z=103) — placed below period 7. Most are radioactive; many are man-made.
3.6 Metals, Non-metals and Metalloids
Apart from being able to classify elements into s, p, d, f-blocks, the elements can also be divided based on their properties into metals, non-metals, and metalloids:
Metals
About 78% of all known elements are metals. They are usually found on the LEFT side and centre of the periodic table.
- Solid at room temperature (except mercury, Hg, which is liquid)
- High melting and boiling points
- Good conductors of heat and electricity
- Malleable (hammered into thin sheets) and ductile (drawn into wires)
- Lustrous appearance
- Tend to lose electrons → form positive ions (cations)
Non-metals
Non-metals are located on the upper RIGHT side of the periodic table.
- Solid, liquid (Br) or gaseous at room temperature
- Low melting and boiling points (except C, B, Si)
- Poor conductors of heat and electricity (except graphite)
- Brittle (in solid form)
- Dull appearance
- Tend to gain electrons → form negative ions (anions)
Metalloids (Semimetals)
Elements with intermediate properties between metals and non-metals are called metalloids. They lie along the diagonal stair-step line: B, Si, Ge, As, Sb, Te, Po.
Industrial significance: Si and Ge are crucial for the semiconductor industry — the basis of all modern electronics! Their position between metals (good conductors) and non-metals (insulators) gives them tunable conductivity.
Worked Examples
Worked Example 1 (NCERT Problem 3.1): IUPAC Name from Z
What would be the IUPAC name and symbol for the element with atomic number 120?
Atomic number: 120 → digits 1, 2, 0.
Roots: un, bi, nil → "unbinilium" + suffix "ium" (already there).
But final form drops the extra "i" between consecutive vowels: Unbinilium.
Symbol: u + b + n = Ubn
Roots: un, bi, nil → "unbinilium" + suffix "ium" (already there).
But final form drops the extra "i" between consecutive vowels: Unbinilium.
Symbol: u + b + n = Ubn
Worked Example 2: Identifying Block from Configuration
Identify the block, period, group, and (if possible) the name of an element with electronic configuration: (a) [Ar] 4s² 3d¹⁰ 4p², (b) [Xe] 6s¹
(a) Outer shell n=4. Last electron in 4p (since p > d in filling order in this case, though 4s and 3d come first). Block: p-block. Period 4. Group: 14 (10 transition + 4s² + 4p²; or 4s² + 4p² = 4 valence; group 14). Element: Germanium (Ge, Z=32).
(b) Outer shell n=6. Last electron in 6s. Block: s-block. Period 6. Group: 1 (alkali metal). Element: Caesium (Cs, Z=55).
(b) Outer shell n=6. Last electron in 6s. Block: s-block. Period 6. Group: 1 (alkali metal). Element: Caesium (Cs, Z=55).
Worked Example 3: Metal vs Non-metal Classification
Classify the following as metal, non-metal or metalloid based on their position in the periodic table: Si, Cs, S, As, Cu, Ar.
Si (Group 14, Period 3): Lies on diagonal stair-step → Metalloid.
Cs (Group 1, Period 6): Far left, alkali metal → Metal.
S (Group 16, Period 3): Top right → Non-metal.
As (Group 15, Period 4): On diagonal stair-step → Metalloid.
Cu (Group 11, Period 4): d-block, centre-left → Metal.
Ar (Group 18, Period 3): Top right, noble gas → Non-metal.
Cs (Group 1, Period 6): Far left, alkali metal → Metal.
S (Group 16, Period 3): Top right → Non-metal.
As (Group 15, Period 4): On diagonal stair-step → Metalloid.
Cu (Group 11, Period 4): d-block, centre-left → Metal.
Ar (Group 18, Period 3): Top right, noble gas → Non-metal.
📐 Activity 3.2 — Electronic Configuration Building
Setup: Take three elements: Z = 17, Z = 19, Z = 26. Without looking up tables, write down their electronic configurations and identify their period, group, and block.
Predict: Will Z = 26 (which is in 3d series) be in period 3 or period 4? Why?
Z = 17: 1s² 2s² 2p⁶ 3s² 3p⁵ = [Ne] 3s² 3p⁵. Period 3, Group 17, p-block. Element: Cl.
Z = 19: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ = [Ar] 4s¹. Period 4, Group 1, s-block. Element: K. Key: 4s fills before 3d (Aufbau).
Z = 26: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁶ = [Ar] 3d⁶ 4s². Period 4 (NOT 3!), Group 8, d-block. Element: Fe. The "3d" is misleading — period number depends on highest n in configuration, which is n=4 (because 4s² is present). The d-block elements lie in periods 4, 5, 6, 7.
🎯 Competency-Based Questions
Q1. The IUPAC name and symbol of the element with atomic number 117 is: L3 Apply
Answer: (b) Ununseptium (Uus). Digits 1,1,7 → un + un + sept + ium = Ununseptium. Symbol: U + u + s = Uus. (Now permanently named Tennessine, Ts.)
Q2. An element X is in Group 17 and Period 4. Predict its electronic configuration and name. L3 Apply
Answer: Period 4 → outermost shell n=4. Group 17 → halogen, configuration ends in ns²np⁵.
Full config: [Ar] 3d¹⁰ 4s² 4p⁵. Element: Bromine (Br, Z=35).
Full config: [Ar] 3d¹⁰ 4s² 4p⁵. Element: Bromine (Br, Z=35).
Q3. Why are elements of group 18 chemically inert despite being atoms? L4 Analyse
Answer: Group 18 (noble gases) have completely filled outer electron shells (ns²np⁶ for Ne and beyond; 1s² for He). This electron configuration is exceptionally stable: (i) very high ionisation enthalpy → reluctant to lose electrons; (ii) zero or near-zero electron gain enthalpy → don't accept electrons; (iii) no unpaired electrons → no covalent bonding tendency. Hence they are chemically inert. (Note: Some heavier noble gases like Xe and Kr can form compounds under extreme conditions.)
Q4. Why is Hydrogen sometimes placed in Group 1 and sometimes shown separately or in Group 17? L5 Evaluate
Answer: Hydrogen has unique properties straddling two groups:
Like Group 1 (alkali metals): 1 valence electron (1s¹), forms +1 ion, forms HCl analogous to NaCl.
Like Group 17 (halogens): Needs only 1 electron to complete its shell (1s²), forms H⁻ (hydride) analogous to Cl⁻, forms diatomic H₂ like Cl₂.
Different periodic tables make different choices. Modern IUPAC tables typically place H above Li (Group 1) but acknowledge its unique nature with a separate placement or annotation. There's no single "right" answer — H is simply unique.
Like Group 1 (alkali metals): 1 valence electron (1s¹), forms +1 ion, forms HCl analogous to NaCl.
Like Group 17 (halogens): Needs only 1 electron to complete its shell (1s²), forms H⁻ (hydride) analogous to Cl⁻, forms diatomic H₂ like Cl₂.
Different periodic tables make different choices. Modern IUPAC tables typically place H above Li (Group 1) but acknowledge its unique nature with a separate placement or annotation. There's no single "right" answer — H is simply unique.
Q5. HOT (Create): Predict the systematic IUPAC name and approximate properties (group, expected valence) of element 137 if it could be synthesized. L6 Create
Sample Solution:
Name: 137 → 1, 3, 7 → un + tri + sept + ium = Untriseptium. Symbol: Uts.
Group prediction: Element 118 (Og) ends period 7. Next period would begin at 119. So 137 = 119 + 18 (down by 18 to period 8). Period 8 likely has new g-block (g-orbitals!). Z = 119 (start, group 1) → 120 (group 2) → 121-138 (g-block, 18 elements). So Z = 137 would be near end of g-block, group 17 (in g-block analog).
Properties: Highly unstable, very brief half-life (μs), would require extreme synthesis conditions. Caveat: Theoretical "island of stability" predictions suggest some super-heavy isotopes near Z = 114 might be longer-lived; Z = 137 is at or beyond the limit predicted by Feynman ("Feynman's stable atomic number limit").
Name: 137 → 1, 3, 7 → un + tri + sept + ium = Untriseptium. Symbol: Uts.
Group prediction: Element 118 (Og) ends period 7. Next period would begin at 119. So 137 = 119 + 18 (down by 18 to period 8). Period 8 likely has new g-block (g-orbitals!). Z = 119 (start, group 1) → 120 (group 2) → 121-138 (g-block, 18 elements). So Z = 137 would be near end of g-block, group 17 (in g-block analog).
Properties: Highly unstable, very brief half-life (μs), would require extreme synthesis conditions. Caveat: Theoretical "island of stability" predictions suggest some super-heavy isotopes near Z = 114 might be longer-lived; Z = 137 is at or beyond the limit predicted by Feynman ("Feynman's stable atomic number limit").
🧠 Assertion–Reason Questions
Choose: (A) Both true, R explains A. (B) Both true, R doesn't explain A. (C) A true, R false. (D) A false, R true.
A: The element with Z = 100 is named Fermium (Fm), but Z = 105 used to be called Unnilpentium.
R: IUPAC's systematic naming applies to elements with Z > 100 until a permanent name is officially adopted.
Answer: (A). Both true; R correctly explains A. Z=100 (Fermium) was named before the IUPAC systematic naming convention; Z=105 was disputed (US: Hahnium, USSR: Nielsbohrium), so IUPAC used "Unnilpentium" until consensus was reached on "Dubnium."
A: Hydrogen is placed in Group 1 of the periodic table.
R: Hydrogen has only one valence electron (1s¹), like other alkali metals.
Answer: (B). Both true; R is one reason, but not the complete explanation. Hydrogen also has properties of Group 17 (it can gain 1 electron to form H⁻, and H₂ is diatomic like halogens). The placement is by convention; H is genuinely unique.
A: The element Iron (Fe, Z=26) is in Period 4.
R: Iron's electronic configuration ends in 3d⁶, hence it belongs to period 3.
Answer: (C). A is TRUE — Fe is in Period 4 (despite involving 3d). R is FALSE — period number is determined by highest n in the configuration, which is 4 (4s²). The d-orbital being filled is "3d" but this represents an inner shell. The d-block of Period 4 fills 3d, the d-block of Period 5 fills 4d, etc.
Frequently Asked Questions — Nomenclature and Electronic Configuration of Elements
How are elements with atomic number greater than 100 named?
Elements with atomic number greater than 100 are named using the IUPAC systematic nomenclature based on Latin-Greek numerical roots: 0=nil, 1=un, 2=bi, 3=tri, 4=quad, 5=pent, 6=hex, 7=sept, 8=oct, 9=enn. Each digit of the atomic number is replaced by its root, and '-ium' is added at the end. The symbol uses the first letter of each root. For example, element 113 is named ununtrium (Uut). After confirmation, these elements receive permanent names; element 113 is now nihonium (Nh). NCERT Class 11 Chemistry covers this temporary naming convention.
What is the s-block of the periodic table?
The s-block consists of Group 1 (alkali metals: Li, Na, K, Rb, Cs, Fr) and Group 2 (alkaline earth metals: Be, Mg, Ca, Sr, Ba, Ra). Their general electronic configuration is ns¹ for Group 1 and ns² for Group 2. They are all metals, soft, low melting, highly reactive (especially towards water) and form ionic compounds easily. They show fixed oxidation states (+1 for Group 1 and +2 for Group 2). NCERT Class 11 Chemistry studies their characteristic reactions and periodic trends in detail.
What is the p-block of the periodic table?
The p-block consists of Groups 13 to 18 of the periodic table, with general electronic configuration ns² np¹ to ns² np⁶. It includes metals (Al, Sn, Pb), metalloids (B, Si, Ge), non-metals (C, N, O) and noble gases. The p-block displays the widest variation in properties, including metallic to non-metallic character, ionic to covalent bonding, and multiple oxidation states. NCERT Class 11 Chemistry introduces the block-wise classification and uses it as a framework for understanding hydrogen and the s/p/d/f groupings.
What is the d-block of the periodic table?
The d-block consists of Groups 3 to 12, also called transition elements, with general electronic configuration (n−1)d¹⁻¹⁰ ns¹⁻². They lie between the s- and p-blocks. Transition metals show variable oxidation states, form coloured compounds, act as catalysts and exhibit paramagnetism. Examples include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn. Some elements like Zn, Cd, Hg with d¹⁰ configurations are sometimes excluded from transition metals strictly. NCERT Class 11 Chemistry covers their position and general electronic configuration as the basis for Class 12 transition element chemistry.
What is the f-block of the periodic table?
The f-block elements, also called inner transition elements, comprise the lanthanides (4f¹⁻¹⁴ 5d⁰⁻¹ 6s²) and actinides (5f¹⁻¹⁴ 6d⁰⁻¹ 7s²). They are shown as separate rows below the main periodic table for compactness. Lanthanides (Ce to Lu) are silvery metals used in alloys, magnets and electronics. Actinides (Th to Lr) are radioactive; uranium and plutonium are nuclear fuels. NCERT Class 11 Chemistry briefly introduces them as the inner transition series with their general configuration; their detailed chemistry is covered in Class 12.
How are valence electrons and groups related?
Valence electrons are the electrons in the outermost shell of an atom and are responsible for chemical bonding and reactivity. The group number in the modern periodic table is directly related to valence electrons for s and p block elements: Group 1 has 1, Group 2 has 2, Group 13 has 3, Group 14 has 4, Group 15 has 5, Group 16 has 6, Group 17 has 7 and Group 18 has 8 valence electrons (except He which has 2). For d-block elements, the (n−1)d electrons also participate in some bonding situations. NCERT Class 11 Chemistry uses this group-valence relationship to predict chemical behaviour.
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