The atomic radius of a particular element is an important characteristic as it helps us to understand many properties of atoms and how they react. Helium is in the top period and the farthest right group, which follows the patterns of atomic radius on the periodic table. Helium has the smallest atomic radius at 31 picometers. Which element has the smallest atomic radius? This means the electrons are pulled more closely to the nucleus, reducing the size of the atomic radius. Thus, as the nuclear charge increases across a period, the protons in the nucleus can attract the higher number of electrons more closely due to the attraction of the positive protons to the negative electrons. Why does the atomic radius decrease across a period?Īcross a period, the number of electron shells remains the same, while the number of electrons increases. This increases the atomic radius as the electrons in the outermost shell are further away from the nucleus. Why does the atomic radius increase as you progress down a group?Īs we progress down a group in the periodic table, the number of electrons increases, and so does the number of shells that those electrons are organized into. The atomic radius is calculated by measuring the distance between the nuclei of two identical atoms bonded together.

Elements in the same period have the same number of electron shells, while elements in the same group have the same number of valence electrons. Periods run across the table horizontally, while groups are the vertical groupings. Elements in the periodic table are organized into periods and groups. The properties of liquid sodium metal make it useful as a coolant in fast breeder reactors and as a heat transfer agent for very high temperature reactions.Refresher: Atoms consist of a nucleus with positively charged protons and neutral neutrons surrounded by shells of electrons. It is used in the manufacture of soap, the refining of petroleum, the manufacture of paper, textiles, rayon, cellulose film, and many other products. Called caustic soda, it is very corrosive to the skin. Sodium hydroxide (NaOH) is a very important laboratory reagent and a widely used industrial chemical. Sodium sulfate is found in mineral form as Thenardite.Ī phosphate of aluminum and sodium is Wardite. 5H 2O) along with tincalconite form vast deposits of boron in California. 4H 2O), and colemanite (calcium hexaborate pentahydrate, Ca 2B 6O 11. 10H 2O), kernite (sodium tetraborate tetrahydrate, Na 2B 4O 7. Sodium borates such as borax (sodium tetraborate decahydrate, Na 2B 4O 7. Sodium chloride is used for the extraction of metallic sodium and gaseous chlorine, as well as for preparation of other compounds of these elements. It is important as an electrolyte in human blood and plasma, which contain about 0.9 grams of NaCl per 100 ml. In crystalline form it is given the mineral name halite. Comprising 3% of sea water and also occurring in large solid deposits and underground salt brines, NaCl is an abundant mineral. The most important compound of sodium is sodium chloride, NaCl (common table salt). It is a constituent of the plagioclase form of feldspar, one of the most abundant minerals on the earth. Sodium is one of the big 8 elements in the Earth's crust, being the sixth most abundant element at about 2.8% by weight. Sodium, like the other alkali metals (Group I), is a sivery-white metal of very high chemical reactivity.

Sodium atomic radius