Period (periodic table)

With a period of the periodic table is understood in the chemical, each row of the Periodic Table of the Elements. The periods Numbers 1-7 correspond to the principal quantum numbers, which often specified periods letter K to Q the shells of the shell model of the atomic shell.

Except for the first period, which contains only the elements hydrogen and helium, each period consists of eight main group elements. From the 4th period (including ) ten subgroup elements are added. The 6th period additionally contains 14 lanthanides, the actinides 7th period 14:


Rules and laws

Within a period usually take from left to right, the atomic radius decreases and the electronegativity, since the number of positively charged protons in the nucleus increases and thus in a neutral atom as well as the number of negatively charged electrons in the atomic shell. When using the shell model while the electron shells are filled, occupied when using a neuereren atomic model such as the orbital model, the corresponding atomic orbitals.

The change in the number of atomic building blocks caused the different properties of the chemical elements within a period:

  • Changing the block numbers in the nucleus causes especially the different physical properties
  • The number and the location of the electrons in the atomic shell effect va the different chemical properties.