Periodic Table of elements – divided to Groups, Periods and Blocks Group 1 18 Groups – Vertical column • Same number of valence electron • Same number outmost electrons Block – different region in periodic table • s, p, d, f blocks • s block- elements with valence e in s sublevel • p block – elements with valence e in p sublevel Period- Horizontal row • 7 periods/row • Same number of shell Periods 1 7 s block - s orbitals partially fill d block • d orbitals partially fill f block • f orbital partially fill p block • p orbital partially fill Excellent site from periodic videos Click here to view
17
Embed
IB Chemistry on Periodic Trends, Effective Nuclear Charge and Physical properties.
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Periodic Table of elements – divided to Groups, Periods and Blocks
Group 1 18
Groups – Vertical column • Same number of valence electron • Same number outmost electrons
Block – different region in periodic table • s, p, d, f blocks • s block- elements with valence e in s sublevel • p block – elements with valence e in p sublevel
Period- Horizontal row • 7 periods/row • Same number of shell
Periods 1 7
s block - s orbitals partially fill
d block • d orbitals partially fill
f block • f orbital partially fill
p block • p orbital partially fill
Excellent site from periodic videos Click here to view
Why atomic radius decrease across period 2/3 Atomic Radius (Covalent radius)
Atomic radius decrease across period 2/3
Effective Nuclear charge increase
Strong electrostatic forces attraction bet nucleus and e
Size decrease
Li
period 2
Atomic Radius- Period 2/3
Be
+4 B
+5 C
+6 N
+7 +3 O
+8
F
+9
Effective Nuclear charge increase
period 3
Na
+11
Mg
+12
AI
+13 Si
+14 P
+15 S
+16
CI
+17
Gp 17
Number shell increase
Valence e further away from nucleus
Atomic radius High
Why atomic radius increase down Gp 17?
Screening/shielding effect increase
Inner shell electrons electron electron repulsion increase
Ionic radii
2.8.8 2.8.8 - 2 shells
2.8.6 2.8.7 - 3 shells
2.8 2.8 2.8 - 2 shells
2.8.1 2.8.2 2.8.3 - 3 shells
Atomic and Ionic Radius- Period 2/3 Positive Ions (+) Negative Ions (-)
Ionic radii Positive ion (+) smaller
Comparison bet atomic/ionic radii
Decrease in number of shells – loss of electron
Less electron electron repulsion
Size decrease
Atomic radii
Ionic radii
Ionic radii Negative ion (-) bigger
Increase in number of shells – gain of electron
Increase electron electron repulsion
Size increase
Comparison bet atomic/ionic radii
Atomic radii
Ionic radii
Na
Na+
Mg
Mg2+
AI
AI3+
Atomic radii
Ionic radii
AI S CI
S2- CI-
Atomic radii
Period 2
Shared electron cloud closer to O
Electronegativity
Electronegativity (EN) • Tendency of atom to attract/pull shared/bonding electron to itself • EN value higher – pull/attract electron higher (EN value from 0.7 – 4)
EN highest EN lowest
Factors affecting EN value • Size of atom/distance – small size/distance – stronger attraction for electron • Nuclear charge – higher nuclear charge – stronger attraction for electron
Electronegativity • EN increase up a Group • EN increase across a Period
F
CI
Br
I
Size increase
Attraction electron decrease
EN lower
Size
Be
+4
Li
+3 B
+5 N
+7
O
+8 F
+9
EN increase across period 2
Nuclear charge
EN increase across period 2 Nuclear charge increase Strong attraction for electron
EN increase
Gp 17
C
+6
EN decrease down gp 17
Melting Point • Temp when solid turn to liquid (temp remain constant) • Energy absorb to overcome forces attraction bet molecule
Factors affecting melting point
• Melting point across Period 2/3 • Melting point down Gp 1/17
Gp 1 Gp 17
Period 2/3
Structure
Metallic/Non Metallic structure
Covalent structure
Giant molecular structure
Type of bonding/forces
Ionic Bonding Covalent Bonding Ionic structure
Simple molecular structure
Metallic Bonding
Melting Point
period 2
period 3
Li
Be
B
C
N O F Ne
Na
Mg AI
Si
P S CI
Melting point across Period 2 and 3
Melting Point Melting point across Period 2
period 2
Van der waals forces bet molecules
Across period 2 • m/p increase from Li – C • m/p drop from N – Ne • Metallic – non metallic
Li Be B C N O F Ne
m/p (/C)
180 1280 2300 3730 -210 -218 -220 -249
structure metallic metallic Giant covalent
Giant covalent
Simple molecular
Simple molecular
Simple molecular
Mono atomic
bonding metallic metallic Giant covalent
Giant covalent
Simple covalent
Simple covalent
Simple covalent
Simple covalent
Li
Be
B
C
N O F Ne
Metallic bonding Giant covalent Simple covalent
Strong attraction bet nucleus with sea of electrons
Macromolecular structure with strong covalent bonds
Simple molecular weak Van Der Waals forces attraction bet molecules
Melting point for metallic/non metallic
High m/p Highest m/p Low m/p
Melting Point Melting point across Period 3
Period 3
Van der waals forces between molecules
Across period 3 • m/p increase from Na – Si • m/p drop from P – Ar • Metallic – non metallic