Chapter 6
Periodic Law
Elements of the periodic table are arranged in order of increasing atomic number
The periodic law states “When elements are arranged in order of increasing atomic number, there is a periodic repetition of their chemical and physical properties.”
Noble Gasses
The noble gases are in Group VIII of the periodic table.
Helium has a full outer shell of two s electrons.
The other gases have full outer shells of two s and six p electrons.
Compounds have been formed with Rn, Xe, Kr, and Ar.
Halogens
The halogens all have seven electrons in their outer shells.
The electron configuration in the outer shell is ns2np5.
As the atomic number increases, the reactivity of the halogens decreases.
Fluorine and chlorine exist as gases at room temperature, while bromine is a liquid, and iodine is a solid.
Atomic Radius
Atomic radius is determined as the distance between the nuclei of two identical atoms bonded together.
The atomic radius of atoms generally decreases from left to right across a period.
The atomic radius of atoms generally increases from top to bottom within a group.
Electron Sheilding
Electron shielding refers to the blocking of valence shell electron attraction by the nucleus due to the presence of inner-shell electrons.
Electrons in an s orbital can shield p electrons at the same energy level because of the spherical shape of the s orbital.
Electrons in paired spin configurations are slightly easier to remove than unpaired electrons.
Metals
Metals: Metals are good conductor for heat and electricity,
and are malleable and ductile.
Non Metals: Poor Conductors of heat and electricity, and are not malleable and ductile
Metalloids: Metalloids are elements with properties intermediate between those of metals and non-metals
Transition Metals: The transition elements are found in groups IIIA-IIB, these elements are characterized by having unfilled d sublevels.
Alkaline Earth Metals: The alkaline earth elements are in Group 2 of the periodic table. These elements each have two s electrons in their outer shell. The alkaline earth elements are less reactive than the alkali metals.
Ion
Ion: Atoms have equal numbers of positive protons and negative electrons, so they are neutral in electric charge. Atoms can gain or lose electrons and become ions, which are atoms that have a positive or negative charge because they have unequal numbers of protons and electrons.
The process in which an atom becomes an ion is called ionization. It may occur when atoms are exposed to high levels of radiation or when atoms transfer electrons to or from other atoms.