Cheat Sheet: Classification of Elements & Periodicity in Properties | Chemistry Class 11 - NEET PDF Download

 Page 1


Classification of Elements and Periodicity
in Properties - Class 11 CBSE
1. Introduction
The Periodic T able organizes elements based on their properties, revealing trends
and grouping them into families. It is essential for understanding chemistry’ s
fundamental building blocks.
2. Historical Development
• Dobereiner ’ s Triads (1829): Groups of three elements with similar prop-
erties; middle element’ s atomic weight is halfwa y between the other two
(e.g., Li, Na, K).
• Newlands’ Law of Octaves (1865): Elements arr anged b y increasing atomic
weight; every eighth element has similar properties (valid up to Ca).
• Mendeleev’ s Periodic T able (1869): Arr anged elements b y increasing atomic
weight, placing similar properties in groups; left gaps for undiscovered el-
ements (e.g., Eka- Aluminium: Ga, Eka-Silicon: Ge).
• Lothar Meyer (1869): Plotted ph ysical properties (e.g., atomic volume) vs.
atomic weight, s howing periodic patterns.
3. Modern Periodic Law
Ph ysical and chemical properties of elements are periodic functions of their atomic
numbers (Z). Proposed b y Henry Moseley (1913), based on X-r a y frequency vs.
atomic number .
4. Structure of the Periodic T able
• Periods: 7 horizontal rows; period number = highest principal quantum
number (n ).
– Period 1: 2 elements (1s)
– Periods 2–3: 8 elements (s, p)
– Periods 4–5: 18 elements (s, p, d)
– Periods 6–7: 32 elements (s, p, d, f; 7th incomplete)
• Groups: 18 vertical columns (1–18, IUP A C); elements with similar valence
shell elec tronic configur ations.
1
Page 2


Classification of Elements and Periodicity
in Properties - Class 11 CBSE
1. Introduction
The Periodic T able organizes elements based on their properties, revealing trends
and grouping them into families. It is essential for understanding chemistry’ s
fundamental building blocks.
2. Historical Development
• Dobereiner ’ s Triads (1829): Groups of three elements with similar prop-
erties; middle element’ s atomic weight is halfwa y between the other two
(e.g., Li, Na, K).
• Newlands’ Law of Octaves (1865): Elements arr anged b y increasing atomic
weight; every eighth element has similar properties (valid up to Ca).
• Mendeleev’ s Periodic T able (1869): Arr anged elements b y increasing atomic
weight, placing similar properties in groups; left gaps for undiscovered el-
ements (e.g., Eka- Aluminium: Ga, Eka-Silicon: Ge).
• Lothar Meyer (1869): Plotted ph ysical properties (e.g., atomic volume) vs.
atomic weight, s howing periodic patterns.
3. Modern Periodic Law
Ph ysical and chemical properties of elements are periodic functions of their atomic
numbers (Z). Proposed b y Henry Moseley (1913), based on X-r a y frequency vs.
atomic number .
4. Structure of the Periodic T able
• Periods: 7 horizontal rows; period number = highest principal quantum
number (n ).
– Period 1: 2 elements (1s)
– Periods 2–3: 8 elements (s, p)
– Periods 4–5: 18 elements (s, p, d)
– Periods 6–7: 32 elements (s, p, d, f; 7th incomplete)
• Groups: 18 vertical columns (1–18, IUP A C); elements with similar valence
shell elec tronic configur ations.
1
• Lanthanoids (Ce–Lu, Z=58–71) and A ctinoids (Th–Lr , Z=90–103) placed
separ ately at the bo ttom.
5. Nomenclature of Elements (Z > 100)
T empor ary IUP A C names use numerical roots (T able 1) until officially named.
Examples:
T able 1: Numerical Roots for IUP A C Nomenclature
Digit Name 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
• Z = 101: Unnilunium (Unu), Mendelevium (Md)
• Z = 118: Ununoctium (Uuo), Oganesson (Og)
• Z = 120 (h y pothetical): Unbinilium (Ubn), [Uuo]8s
2
6. Electronic Configur ations and Block Classification
Elements classified into s-, p-, d-, f-blocks based on the orbital of the last electron.
s-Block (Groups 1–2): ns
1
–ns
2
; alkali (Group 1) and alkaline earth metals
(Group 2); reactive, low ionization enthalpies, ionic compounds (except Li,
Be). p-Block (Groups 13–18): ns
2
np
1
–ns
2
np
6
; includes non-metals, met-
alloids, noble gases (ns
2
np
6
); non-metallic char acter increases across pe-
riod. d-Block (Groups 3–12): (n-1)d
1
–
10
ns
0
–
2
; tr ansition metals; coloured
ions, variable oxidation states, catalytic properties (except Zn, Cd, Hg). f-
Block (Lanthanoids, A ctinoids): (n-2)f
1
–
14
(n-1)d
0
–
1
ns
2
; inner-tr ansition
metals; similar properties within series; actinoids are r adioactive.
Exceptions:
• He: s-block but placed in Group 18 (noble gases, 1s
2
).
• H: Unique; pl aced separ ately (1s
1
; behaves lik e Group 1 or 17).
2
Page 3


Classification of Elements and Periodicity
in Properties - Class 11 CBSE
1. Introduction
The Periodic T able organizes elements based on their properties, revealing trends
and grouping them into families. It is essential for understanding chemistry’ s
fundamental building blocks.
2. Historical Development
• Dobereiner ’ s Triads (1829): Groups of three elements with similar prop-
erties; middle element’ s atomic weight is halfwa y between the other two
(e.g., Li, Na, K).
• Newlands’ Law of Octaves (1865): Elements arr anged b y increasing atomic
weight; every eighth element has similar properties (valid up to Ca).
• Mendeleev’ s Periodic T able (1869): Arr anged elements b y increasing atomic
weight, placing similar properties in groups; left gaps for undiscovered el-
ements (e.g., Eka- Aluminium: Ga, Eka-Silicon: Ge).
• Lothar Meyer (1869): Plotted ph ysical properties (e.g., atomic volume) vs.
atomic weight, s howing periodic patterns.
3. Modern Periodic Law
Ph ysical and chemical properties of elements are periodic functions of their atomic
numbers (Z). Proposed b y Henry Moseley (1913), based on X-r a y frequency vs.
atomic number .
4. Structure of the Periodic T able
• Periods: 7 horizontal rows; period number = highest principal quantum
number (n ).
– Period 1: 2 elements (1s)
– Periods 2–3: 8 elements (s, p)
– Periods 4–5: 18 elements (s, p, d)
– Periods 6–7: 32 elements (s, p, d, f; 7th incomplete)
• Groups: 18 vertical columns (1–18, IUP A C); elements with similar valence
shell elec tronic configur ations.
1
• Lanthanoids (Ce–Lu, Z=58–71) and A ctinoids (Th–Lr , Z=90–103) placed
separ ately at the bo ttom.
5. Nomenclature of Elements (Z > 100)
T empor ary IUP A C names use numerical roots (T able 1) until officially named.
Examples:
T able 1: Numerical Roots for IUP A C Nomenclature
Digit Name 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
• Z = 101: Unnilunium (Unu), Mendelevium (Md)
• Z = 118: Ununoctium (Uuo), Oganesson (Og)
• Z = 120 (h y pothetical): Unbinilium (Ubn), [Uuo]8s
2
6. Electronic Configur ations and Block Classification
Elements classified into s-, p-, d-, f-blocks based on the orbital of the last electron.
s-Block (Groups 1–2): ns
1
–ns
2
; alkali (Group 1) and alkaline earth metals
(Group 2); reactive, low ionization enthalpies, ionic compounds (except Li,
Be). p-Block (Groups 13–18): ns
2
np
1
–ns
2
np
6
; includes non-metals, met-
alloids, noble gases (ns
2
np
6
); non-metallic char acter increases across pe-
riod. d-Block (Groups 3–12): (n-1)d
1
–
10
ns
0
–
2
; tr ansition metals; coloured
ions, variable oxidation states, catalytic properties (except Zn, Cd, Hg). f-
Block (Lanthanoids, A ctinoids): (n-2)f
1
–
14
(n-1)d
0
–
1
ns
2
; inner-tr ansition
metals; similar properties within series; actinoids are r adioactive.
Exceptions:
• He: s-block but placed in Group 18 (noble gases, 1s
2
).
• H: Unique; pl aced separ ately (1s
1
; behaves lik e Group 1 or 17).
2
7. Metals, Non-metals, Metalloids
• Metals (>78%): Left side; high melting/boiling points, conductors, malleable,
ductile.
• Non-metals: T op-right; low melting/boiling points, poor conductors, brit-
tle.
• Metalloids ( Si, Ge, As, Sb, T e): Diagonal border; intermediate properties.
• Metallic char a cter: Increases down a group, decreases across a period.
3
Page 4


Classification of Elements and Periodicity
in Properties - Class 11 CBSE
1. Introduction
The Periodic T able organizes elements based on their properties, revealing trends
and grouping them into families. It is essential for understanding chemistry’ s
fundamental building blocks.
2. Historical Development
• Dobereiner ’ s Triads (1829): Groups of three elements with similar prop-
erties; middle element’ s atomic weight is halfwa y between the other two
(e.g., Li, Na, K).
• Newlands’ Law of Octaves (1865): Elements arr anged b y increasing atomic
weight; every eighth element has similar properties (valid up to Ca).
• Mendeleev’ s Periodic T able (1869): Arr anged elements b y increasing atomic
weight, placing similar properties in groups; left gaps for undiscovered el-
ements (e.g., Eka- Aluminium: Ga, Eka-Silicon: Ge).
• Lothar Meyer (1869): Plotted ph ysical properties (e.g., atomic volume) vs.
atomic weight, s howing periodic patterns.
3. Modern Periodic Law
Ph ysical and chemical properties of elements are periodic functions of their atomic
numbers (Z). Proposed b y Henry Moseley (1913), based on X-r a y frequency vs.
atomic number .
4. Structure of the Periodic T able
• Periods: 7 horizontal rows; period number = highest principal quantum
number (n ).
– Period 1: 2 elements (1s)
– Periods 2–3: 8 elements (s, p)
– Periods 4–5: 18 elements (s, p, d)
– Periods 6–7: 32 elements (s, p, d, f; 7th incomplete)
• Groups: 18 vertical columns (1–18, IUP A C); elements with similar valence
shell elec tronic configur ations.
1
• Lanthanoids (Ce–Lu, Z=58–71) and A ctinoids (Th–Lr , Z=90–103) placed
separ ately at the bo ttom.
5. Nomenclature of Elements (Z > 100)
T empor ary IUP A C names use numerical roots (T able 1) until officially named.
Examples:
T able 1: Numerical Roots for IUP A C Nomenclature
Digit Name 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
• Z = 101: Unnilunium (Unu), Mendelevium (Md)
• Z = 118: Ununoctium (Uuo), Oganesson (Og)
• Z = 120 (h y pothetical): Unbinilium (Ubn), [Uuo]8s
2
6. Electronic Configur ations and Block Classification
Elements classified into s-, p-, d-, f-blocks based on the orbital of the last electron.
s-Block (Groups 1–2): ns
1
–ns
2
; alkali (Group 1) and alkaline earth metals
(Group 2); reactive, low ionization enthalpies, ionic compounds (except Li,
Be). p-Block (Groups 13–18): ns
2
np
1
–ns
2
np
6
; includes non-metals, met-
alloids, noble gases (ns
2
np
6
); non-metallic char acter increases across pe-
riod. d-Block (Groups 3–12): (n-1)d
1
–
10
ns
0
–
2
; tr ansition metals; coloured
ions, variable oxidation states, catalytic properties (except Zn, Cd, Hg). f-
Block (Lanthanoids, A ctinoids): (n-2)f
1
–
14
(n-1)d
0
–
1
ns
2
; inner-tr ansition
metals; similar properties within series; actinoids are r adioactive.
Exceptions:
• He: s-block but placed in Group 18 (noble gases, 1s
2
).
• H: Unique; pl aced separ ately (1s
1
; behaves lik e Group 1 or 17).
2
7. Metals, Non-metals, Metalloids
• Metals (>78%): Left side; high melting/boiling points, conductors, malleable,
ductile.
• Non-metals: T op-right; low melting/boiling points, poor conductors, brit-
tle.
• Metalloids ( Si, Ge, As, Sb, T e): Diagonal border; intermediate properties.
• Metallic char a cter: Increases down a group, decreases across a period.
3
8. Periodic Trends in Ph ysical Properties
(a) Atomic Radius:
• Decreases across period: Same valence shell, increasing nuclear
charge.
• Increases down group: Highern , more shielding.
• Covalent r adius (non-metals): Half bond distance (e.g., Cl: 99 pm).
• Metallic r adius (metals): Half internuclear distance (e.g., Cu: 128
pm).
(b) Ionic Radius:
• Cations: Smaller than parent atom (e.g., Na
+
: 95 pm vs. Na: 186 pm).
• Anions: Larger than parent atom (e.g., F
-
: 136 pm vs. F: 64 pm).
• Isoelectronic species: Smaller r adius with higher nuclear charge
(e.g., Mg
2+
< Na
+
).
(c) Ionization Enthalp y (?
i
H ):
• Energy to remove elec tron: X(g)? X
+
(g) + e
-
.
• Increases across period: Higher nuclear charge, less shielding.
• Decreases down group: Larger size, more shielding.
• Exceptions: B < Be (2p vs. 2s); O < N (electron repulsion in 2p).
(d) Electron Gain Enthalp y (?
eg
H ):
• Energy change: X(g) + e
-
? X
-
(g).
• More neg ative across period: Smaller size, hi gher nuclear charge.
• Less neg ative down group: Larger size.
• Exceptions: O , F less negative than S, Cl (electron repulsion in n=2).
(e) Electronegativity (Pauling Scale):
• Ability to attr act s hared electrons (e.g., F: 4.0, Li: 1.0).
• Increases across period: Smaller size, higher nuclear charge.
• Decreases down group: Larger size.
• Correlates with non-metallic char acter (increases across, decreases
down).
4
Page 5


Classification of Elements and Periodicity
in Properties - Class 11 CBSE
1. Introduction
The Periodic T able organizes elements based on their properties, revealing trends
and grouping them into families. It is essential for understanding chemistry’ s
fundamental building blocks.
2. Historical Development
• Dobereiner ’ s Triads (1829): Groups of three elements with similar prop-
erties; middle element’ s atomic weight is halfwa y between the other two
(e.g., Li, Na, K).
• Newlands’ Law of Octaves (1865): Elements arr anged b y increasing atomic
weight; every eighth element has similar properties (valid up to Ca).
• Mendeleev’ s Periodic T able (1869): Arr anged elements b y increasing atomic
weight, placing similar properties in groups; left gaps for undiscovered el-
ements (e.g., Eka- Aluminium: Ga, Eka-Silicon: Ge).
• Lothar Meyer (1869): Plotted ph ysical properties (e.g., atomic volume) vs.
atomic weight, s howing periodic patterns.
3. Modern Periodic Law
Ph ysical and chemical properties of elements are periodic functions of their atomic
numbers (Z). Proposed b y Henry Moseley (1913), based on X-r a y frequency vs.
atomic number .
4. Structure of the Periodic T able
• Periods: 7 horizontal rows; period number = highest principal quantum
number (n ).
– Period 1: 2 elements (1s)
– Periods 2–3: 8 elements (s, p)
– Periods 4–5: 18 elements (s, p, d)
– Periods 6–7: 32 elements (s, p, d, f; 7th incomplete)
• Groups: 18 vertical columns (1–18, IUP A C); elements with similar valence
shell elec tronic configur ations.
1
• Lanthanoids (Ce–Lu, Z=58–71) and A ctinoids (Th–Lr , Z=90–103) placed
separ ately at the bo ttom.
5. Nomenclature of Elements (Z > 100)
T empor ary IUP A C names use numerical roots (T able 1) until officially named.
Examples:
T able 1: Numerical Roots for IUP A C Nomenclature
Digit Name 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
• Z = 101: Unnilunium (Unu), Mendelevium (Md)
• Z = 118: Ununoctium (Uuo), Oganesson (Og)
• Z = 120 (h y pothetical): Unbinilium (Ubn), [Uuo]8s
2
6. Electronic Configur ations and Block Classification
Elements classified into s-, p-, d-, f-blocks based on the orbital of the last electron.
s-Block (Groups 1–2): ns
1
–ns
2
; alkali (Group 1) and alkaline earth metals
(Group 2); reactive, low ionization enthalpies, ionic compounds (except Li,
Be). p-Block (Groups 13–18): ns
2
np
1
–ns
2
np
6
; includes non-metals, met-
alloids, noble gases (ns
2
np
6
); non-metallic char acter increases across pe-
riod. d-Block (Groups 3–12): (n-1)d
1
–
10
ns
0
–
2
; tr ansition metals; coloured
ions, variable oxidation states, catalytic properties (except Zn, Cd, Hg). f-
Block (Lanthanoids, A ctinoids): (n-2)f
1
–
14
(n-1)d
0
–
1
ns
2
; inner-tr ansition
metals; similar properties within series; actinoids are r adioactive.
Exceptions:
• He: s-block but placed in Group 18 (noble gases, 1s
2
).
• H: Unique; pl aced separ ately (1s
1
; behaves lik e Group 1 or 17).
2
7. Metals, Non-metals, Metalloids
• Metals (>78%): Left side; high melting/boiling points, conductors, malleable,
ductile.
• Non-metals: T op-right; low melting/boiling points, poor conductors, brit-
tle.
• Metalloids ( Si, Ge, As, Sb, T e): Diagonal border; intermediate properties.
• Metallic char a cter: Increases down a group, decreases across a period.
3
8. Periodic Trends in Ph ysical Properties
(a) Atomic Radius:
• Decreases across period: Same valence shell, increasing nuclear
charge.
• Increases down group: Highern , more shielding.
• Covalent r adius (non-metals): Half bond distance (e.g., Cl: 99 pm).
• Metallic r adius (metals): Half internuclear distance (e.g., Cu: 128
pm).
(b) Ionic Radius:
• Cations: Smaller than parent atom (e.g., Na
+
: 95 pm vs. Na: 186 pm).
• Anions: Larger than parent atom (e.g., F
-
: 136 pm vs. F: 64 pm).
• Isoelectronic species: Smaller r adius with higher nuclear charge
(e.g., Mg
2+
< Na
+
).
(c) Ionization Enthalp y (?
i
H ):
• Energy to remove elec tron: X(g)? X
+
(g) + e
-
.
• Increases across period: Higher nuclear charge, less shielding.
• Decreases down group: Larger size, more shielding.
• Exceptions: B < Be (2p vs. 2s); O < N (electron repulsion in 2p).
(d) Electron Gain Enthalp y (?
eg
H ):
• Energy change: X(g) + e
-
? X
-
(g).
• More neg ative across period: Smaller size, hi gher nuclear charge.
• Less neg ative down group: Larger size.
• Exceptions: O , F less negative than S, Cl (electron repulsion in n=2).
(e) Electronegativity (Pauling Scale):
• Ability to attr act s hared electrons (e.g., F: 4.0, Li: 1.0).
• Increases across period: Smaller size, higher nuclear charge.
• Decreases down group: Larger size.
• Correlates with non-metallic char acter (increases across, decreases
down).
4
9. Periodic Trends in Chemical Properties
(a) V alence/Oxidation State:
• Representative elements: V alence = valence electrons or 8 – valence
electrons.
• Oxidation state based on electronegativity (e.g., O: +2 in OF
2
, –2 in
Na
2
O).
• V ariable valenc e in tr ansition elements and actinoids.
(b) Anomalous Properties of Second Period (Li, Be, B–F):
• Small size, hi gh charge/r adius r atio, high electronegativity .
• Li, Be form covalen t compounds; others form ionic.
• Limited valence or bitals (2s, 2p; max covalency 4, e.g., [BF
4
]
–
).
• Strong pp –pp multiple bonds (e.g., C=C, N?N).
• Diagonal rel ationship (e.g., Li–Mg, Be–Al).
(c) Chemical Reactivity:
• Highest at period extremes: Group 1 (low ?
i
H ), Group 17 (high
?
eg
H ).
• Lowest in centr e (Groups 13–14).
• Oxides: Basic (left, e.g., Na
2
O), acidic (right, e.g., Cl
2
O
7
), ampho-
teric/neutr al (cen tre, e.g., Al
2
O
3
, CO).
• Metallic char a cter: Increases down group, decreases across period.
5