University:
California State University, Northridge
Course:
CHEM 100 | Principles of Chemistry
Academic year:

2023
Views:

86

Pages:

1
Author:

SMauren

THIRD PERIOD 1. Physical Properties of the Third Period Elements The elements in the third period consist of metal elements (Na, Mg, Al), metalloids (Si), nonmetals (P, S, Cl), and noble gases (Ar). The greater the electronegativity of the third period elements to the right due to the smaller the atomic radius to the right. The strength of interatomic bonds in metals increases (from Na to Al). This is related to the increase in valence electrons. Silicon is a semiconductor/insulator because it is a metalloid. This element has very large covalent bonds, as does phosphorus, sulfur and chlorine which are insulators because they are non-metallic 2. Chemical Properties of the Third Period Sodium is the strongest reducing agent, while chlorine is the strongest oxidizing agent. Although sodium, magnesium, and aluminum are strong reducing agents, their reactivity decreases from Na to Al. Meanwhile, silicon is a very weak reducing agent, so it can only react with strong oxidizing agents, for example chlorine and oxygen. On the other hand, apart from being a reducing agent, phosphorus is also a weak oxidizing agent that can oxidize strong reducing agents, such as active metals. Meanwhile, sulfur, which has a weaker reducing power than phosphorus, turns out to have a stronger oxidizing power than phosphorus. While chlorine can oxidize almost all metals and non-metals because chlorine is a strong oxidizing agent. The hydroxide elements of the third period are NaOH, Mg(OH)2 , Al(OH)3 , H2 SiO3 , H3 PO4 , H2 SO4 , and HClO4 . The properties of the hydroxides of the elements of the third period depend on their ionization energy. This can be seen from the type of bond. If the M – OH bond is ionic and the hydroxide is basic because it will release OH– ions in water, then the ionization energy is low. But if the M – OH bond is covalent and can no longer release the OH– ion,so the ionization energy is large. NaOH is classified as a strong base and dissolves easily in water, Mg(OH)2 is weaker than NaOH but is still a strong base. However, Al(OH)3 is amphoteric, meaning it can be both acidic and basic. This means that if Al(OH)3 is in a strong basic environment, it will act as an acid, whereas if it is in a strong acidic environment, it will act as a base. Meanwhile, H2 SiO3 or Si(OH)4 , is a weak and unstable acid, easily decomposing into SiO2 and H2 O. Likewise with H3 PO4 or P(OH)5 which is also a weak acid. While H2 SO4 or S(OH)6 is a strong acid, so is HClO4 or Cl(OH)7 which is a very strong acid (Source: www.chem-is-try.org).

Third Period - Study Notes

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