The dynamic mechanical properties of finite two-dimensional periodic cellular materials are investigated by finite element eigenmode analysis for different architectures of the unit cell. Frequency band gaps are examined in quadratic and hexagonal lattice topologies with regular, inverted, and chiral architecture. Pronounced band gaps develop for chiral lattices. The formation of band gaps can be traced back to the resonance behavior of the elementary building blocks of the cellular structure for different boundary conditions (mode transition). Based on the findings of this work periodic lattice materials with specific band gaps can be designed.