Size of Atoms - Trends : Size of Atoms - Trends
Atomic Radii : Atomic Radii Li Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te Sb Sn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B IA IIA IIIA IVA VA VIA VIIA
Slide 3 : Li Na K Rb Cs La Xe Kr Zn Cl F He H 3d
transition
series 4d
transition
series 0.3 0.25 0.2 0.15 0.1 0.05 0 0 10 20 30 40 50 60 atomic number atomic radius
Periodic Trends in Atomic Radii : Periodic Trends in Atomic Radii LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 175
Relative Size of Atoms : Relative Size of Atoms Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 350
Attraction and Repulsion of Electrical Charges : Attraction and Repulsion of Electrical Charges + + Particles with opposite
charges attract
one another. Particles with like charges
repel one another. - - + -
Coulombic Attraction : Coulombic Attraction 1+ 1- 2+ 2- 4- 3- 2+ 2- Coulombic Attraction
1) Charge
opposites attract
like repels
2) Distance A B C D
Shielding Effect : Shielding Effect Kernel electrons block the attractive force of the nucleus from the valence electrons + nucleus Valence Electrons - - - - Electron
Shield
“kernel”
electrons
Shielding Effect and Effective Nuclear Charge : Shielding Effect and Effective Nuclear Charge + _ Mg = [Ne]3s2 Hill, Petrucci, General Chemistry An Integrated Approach 2nd Edition, page 336
Decreasing Atomic Size Across a Period : + + + + + + + + Decreasing Atomic Size Across a Period As the attraction between the (+) nucleus and the (–) valence electrons ?, the atomic size ?. Greater coulombic attraction.
From left to right, size decreases because there is an increase in nuclear charge and Effective Nuclear Charge (# protons – # core electrons).
Each valence electron is pulled by the full ENC (ENC = 1) + + + (ENC = 2) + Li Be (ENC = 3) B 1s22s1 1s22s2 1s22s22p1 Li Be B
Sizes of ions: electron repulsion : Sizes of ions: electron repulsion Valence electrons repel each other. When an atom becomes a anion (adds an electron to its valence shell) the repulsion between valence electrons increases without changing ENC
Thus, F– is larger than F Fluorine atom
F
1s22s22p5 F1-
1s22s22p6 +1e- Fluorine ion Fluoride ion
Atomic Radius of Atoms : Atomic Radius of Atoms Na K Rb Cs Cl S P Si Al Br Se As Ge Ga I Te Sb Sn In Tl Pb Bi Mg Ca Sr Ba Be F O N C B
Atomic Radii : Atomic Radii IA IIA IIIA IVA VA VIA VIIA Ionic Radii
Atomic Radii : Atomic Radii VIIIA
Ionic Radii : Ionic Radii
Trends in Atomic and Ionic Size : Trends in Atomic and Ionic Size Metals Nonmetals Group 1 Group 17 Cations are smaller than parent atoms Anions are larger than parent atoms Al3+
Slide 17 : e e e Li Lithium atom Lithium ion + Li Energy
Slide 18 : IA IIA IIIA IVA VA VIA VIIA Atomic
Radii Ionic
Radii Cations: smaller
than parent atoms Anions: LARGER
than parent atoms
The Octet Rule and Common Ions : The Octet Rule and Common Ions Oxygen atom
O
1s22s22p4 Fluorine atom
F
1s22s22p5 Sodium atom
Na
1s22s22p63s1 Magnesium atom
Mg
1s22s22p63s2 Oxygen ion
O2-
1s22s22p6 Fluorine ion
F1-
1s22s22p6 Sodium ion
Na1+
1s22s22p6 Magnesium ion
Mg2+
1s22s22p6 Neon atom
Ne
1s22s22p6
Isoelectronic Species : Isoelectronic Species Oxygen ion
O2-
1s22s22p6 Fluorine ion
F1-
1s22s22p6 Sodium ion
Na1+
1s22s22p6 Magnesium ion
Mg2+
1s22s22p6 Neon atom
Ne
1s22s22p6 Isoelectronic - all species have the same number of electrons. Can you come up with another isoelectronic series of five elements? p = 8
n = 8
e = 10 p = 9
n = 9
e = 10 p = 10
n = 10
e = 10 p = 11
n = 11
e = 10 p = 12
n = 12
e = 10
Lewis Structure : Lewis Structure Na Cl X o o o o o o o H C N o X X X X D D D D D Cl Na H C N Cl Na H C N Gilbert Lewis “Lewis Dot Notation”
Atomic Radius vs. Atomic Number : Atomic Radius vs. Atomic Number Li Na K Rb Cs La Xe Kr Zn Cl F He H 3d
transition
series 4d
transition
series 0.3 0.25 0.2 0.15 0.1 0.05 0 0 10 20 30 40 50 60 atomic number atomic radius