1. Elements, Compounds and Mixtures ELEMENTS

9. Metals Metals account for about two thirds of all the elements and about 24% of the mass of the planet. Metals have useful properties including strength, ductility, high melting points, thermal and electrical conductivity, and toughness.

10. Non-metals Oxygen atom Sulfur Non-metals tend to be brittle and non-conductive of heat or electricity

11. Metalloids (Si) Silicon is a metalloid Metalloids are also semiconductors

20. Every Compound Has a Unique Set of Properties Physical properties of sodium Standard state : solid at 298 K Color: silvery white

21. Every Compound Has a Unique Set of Properties Chlorine is a greenish yellow gas which combines directly with nearly all elements. Chlorine is a respiratory irritant. The gas irritates the mucous membranes and the liquid burns the skin. As little as 3.5 ppm can be detected as an odor, and 1000 ppm is likely to be fatal after a few deep breaths. It was used as a war gas in 1915. It is not found in a free state in nature, but is found commonly as NaCl (solid or seawater).

22. Sodium chloride General Systematic name Sodium chloride Other names Common salt, halite , table salt Chemical formula Na Cl Molar mass 58.442 g/mol Appearance white and crystalized Properties Density and phase 2.16 g/cm³, solid Solubility in water 35.9 g/100 ml (25 °C) Melting point 801 °C (1074 K) Boiling point 1465 °C (1738 K) General Name , symbol , number sodium, Na, 11 Chemical series alkali metals Group , period , block 1 , 3 , s Appearance silvery white Standard atomic weight 22.98976928 (2) g·mol −1 Electrons per shell 2, 8, 1 Physical properties Phase solid Density 0.968 g·cm −3 Liquid density 0.927 g·cm −3 Melting point 370.87 K (97.72 ° C , 207.9 ° F ) Boiling point 1156 K (883 ° C , 1621 ° F ) General Name , symbol , number chlorine, Cl, 17 Chemical series halogens Group , period , block 17 , 3 , p Appearance yellowish green Standard atomic weight 35.453 (2) g·mol −1 Electrons per shell 2, 8, 7 Physical properties Phase gas Density (0 °C, 101.325 kPa) 3.2 g/L Melting point 171.6 K (-101.5 ° C , -150.7 ° F ) Boiling point 239.11 K (-34.04 ° C , -29.27 ° F )