Practice 3. Talking about Chromium and sodium

Now in laboratory class, I have choose two elements on the periodic table and explain this properties, principal fields of aplications, chemical properties, phisical properties...

My two elements are: Chromium and sodium.

The first element, has a melting point of 1857+/-20°C, boiling point of 2672°C, specific gravity of 7.18 to 7.20 (20°C), with valences usually 2, 3, or 6 (When appears with valence 3, the chromium is benign for humans and lifes, because when appears with valence 6, is toxic and produces cancer and others diseases). The metal is a lustous steel-gray color which takes a high polish. It is hard and resistant to corrosion. In addition chromium has a high melting point, stable crystalline structure, and moderate thermal expansion. All chromium compounds are colored.

The sodium is used to produce soda and also in many industrial processes. The sodium obtained by electrolysis (also sodium is relatively abundant in the sun and other stars). Sodium chloride is important for animal nutrition. Sodium compounds are used in the glass, soap, paper, textile, chemical, petroleum, and metal industries.

Has a melting point of 97.81 +/- 0.03°C, boiling point of 882.9°C, specific gravity of 0.971 (20°C), and a valence of 1 ( always ). It is soft and highly reactive.