Plot the melting and boiling points of Period 3 elements and describe the trends.

• The horizontal axis (x-axis) should be labeled "Atomic Number" or "Element" and range from 11 (Na) to 18 (Ar).
• The vertical axis (y-axis) should be labeled "Temperature ($^\circ$C)" and cover a range from approximately $-200\,^\circ\text{C}$ to $2500\,^\circ\text{C}$ to accommodate all given values.

Plot the following points and connect them to form the melting point curve:

• Na: $(11, 97.8)$
• Mg: $(12, 650)$
• Al: $(13, 660.3)$
• Si: $(14, 1410)$
• P: $(15, 44.1)$
• S: $(16, 112.8)$
• Cl: $(17, -101.5)$
• Ar: $(18, -189.4)$

Plot the following points on the same axes and connect them to form the boiling point curve (use a different line style or color):

• Na: $(11, 882.8)$
• Mg: $(12, 1091)$
• Al: $(13, 2470)$
• Si: $(14, 2355)$
• P: $(15, 280.5)$
• S: $(16, 444.6)$
• Cl: $(17, -34.4)$
• Ar: $(18, -185.8)$

The graph will show two curves, one for melting points and one for boiling points, both following a similar trend across Period 3:

• Both melting and boiling points increase from Sodium (Na) to Aluminum (Al).
• They reach their highest values at Silicon (Si), which has a giant covalent structure.
• After Silicon, both melting and boiling points decrease sharply for Phosphorus (P), Sulfur (S), and Chlorine (Cl), which are simple molecular substances.
• The lowest melting and boiling points are observed for Argon (Ar), a monatomic noble gas.

The overall shape of both curves will be an initial rise, a peak at Silicon, and then a steep decline towards Argon.