3A+Tara

Periodic Trends; Melting Points And Boiling Points. When an element reaches melting point or boiling point the attraction between particles are loosened or broken. This allows the atoms to move more freely but are still connected. The stronger the bonds the more energy required to loosen them. As a generalisation metals have high melting and boiling points and nonmentals have low melting and boiling points. Carbon (non metal) has the highest boiling point. This trend is shown in the periodic table. The periodic table above is colour coded in where each type of element is. As you can see the alkaline metals are in the first group and the noblegases is the last group. This has to do with the number of valence electrons (represented by groups) and the atomic number (number of protons- which are in order). Upon crossing a period, the atom size decreases while decending a group, the atom size increases. The atomic size decreasing is due to the attraction between electrons and nucleus. the larger the distance the less attraction. The above graph showcases the melting and boiling point of all the elements in the periodic table(1 to 95), using thier atomic number. As you can see the pattern its self is an 'Up, down" pattern. Appriximately, every 10 there is a low for both melting and boiling points and every 5 a high point. There are a few inconsistancies with the pattern. The above data shows an inconsistancy with the trend. There is an increase of melting points and boiling points in this group of elements. This spike in meling and boiling points is caused by the variation of bond types in the elements. Sodium, aluminium and magnesium are all metals- which means they have metallic bonding. Metallic bonding is where positive metal ions are attracted to delocalised electrons. Metals tend to have high melting and boiling points. Silicon has a very high melting and boiling point due to it being a metaliod. The bonding between silicon atoms is similar to covalent bonding. One silicon atom is covalently bonded with four other silicon atoms in a tetrahedral stype shape. Strong covalent bonds require a large amount of energy to be broken. Phosphorus,Chlorine and Argon are all non-metals and tend to exist as tiny seperate molecules. Argon is monotomic- which means each atom exists seperately while phosphorus and Chlorine have covalent bonds.
 * = element ||= proton number ||= symbol ||= melting Point ||= Boiling Point ||
 * = sodium ||= 11 ||= Na ||= 371 ||= 1156 ||
 * = magnesium ||= 12 ||= Mg ||= 922 ||= 1380 ||
 * = aluminium ||= 13 ||= Al ||= 933 ||= 2740 ||
 * = silicon ||= 14 ||= Si ||= 1683 ||= 2628 ||
 * = phosphorus ||= 15 ||= P ||= 317 ||= 553 ||
 * = sulfur ||= 16 ||= S ||= 392 ||= 718 ||
 * = chlorine ||= 17 ||= Cl ||= 172 ||= 238 ||
 * = argon ||= 18 ||= Ar ||= 84 ||= 87 ||

Each type of element has a different pattern: Alkali:Relatively low melting and boiling points, which decrease upon decending the group. Alkaline Earth Metals:Similar to the alkali group but has no consistant pattern. Transition: High melting and boiling points that increase with the decrease of atomic number. Lanthanoids and Actinoids: No visible pattern Noble Gases and Halogens: Has very low melting and boiling points that are very close together. The melting and boiling points increase as the atomic number decreases.

[|www.creative-chemistry.org.uk/alevel/module1/trends8.htm] [|www.chemguide.co.uk/atoms] [|www.bbc.co.uk/scotland/learning/bitesize/higher/chemistry/energy/patterns-revl.s.html] [|www.webelements.com/periodically/boiling_point/] [] [] [] []