Chemistry - 3D Structures of Crystalline Structures

molecular solids

held together by intermolecular forces; soft; low melting points

ionic solids

held together by electrostatic attractions; hard and brittle; high melting points; exist as solids at room temperature; only good electrical conductors when molten or dissolved.

atomic solids

metallic, network, and group 8A

metallic solids

held together by metallic bonding; has a range of physical properties; malleable; good conductors of heat and electricity

network solids

exist as a huge macroscopic structure; strong; extremely high melting temperatures

group 8A solids

noble gases; rarely form solids under normal conditions; exhibit weak van der Waals forces

crystal lattices

three-dimensional arrangements of atoms or molecules in a repeating pattern, defining the structure of crystalline solids; each molecule, ion, or atom that makes up the solid is represented by lattice points

simple cubic arrangement

a crystal structure where atoms are positioned at the corners of a cube; 1 atom/unit cell; occupies 52% of space; only happens in Polonium; coordination number = 6

body-centered cubic arrangement

a crystal structure where one atom is positioned at the center of the cube in addition to the atoms at the corners; 2 atoms/unit cell; occupies 68% of space; coordination number = 8

face centered cubic arrangement

a crystal structure where atoms are arranged in a repeating pattern with layers that alternate between two different orientations; 4 atoms/unit cell; occupies 74% of space; coordination number = 12

simple cubic edge length calculations

l = 2r

body-centered cubic edge length calculations

l = 4r/sqrt(3)

face-centered cubic edge length calculations

l = sqrt(8)r

hexagonal close-packed cubic arrangement

coordination number = 12; 2 atoms/unit cell; occupies 74% of space

cubic array arrangement

coordination number = 4; fills 68% of space

simple cubic packing

coordination number = 6; fills 74% of space

Cesium Chloride structure CsCl (+1, -1)

coordination number = 8; simple cubic arrangements; 1 cation + 1 anion/unit cell

Rock Salt structure NaCl (Na+ Cl-)

coordination number = 6; octahedral structure (from face-centered structure, packed differently); 4 cations + 4 anions/unit cell

Zinc Blende structure ZnS (Zn2+, S2-)

coordination number = 4; tetrahedral structure (from face-centered structure, packed differently); 4 cations/unit cell + 4 anions/unit cell

Fluorite structure CaF2 (Ca2+, F-）

coordination number = 8, 4 (cation, anion) cubic structure when cation is in the center and face-centered structure when anion is in the center; 4 cations + 8 anions/unit cell

Antifluorite structure Li2O (Li+, O2-)

coordination number = 4, 8 (cation, anion) cubic structure when anion is in the center and face-centered structure when cation is in the center; 8 cations + 4 anions/unit cell