Question:
Complete the following table to determine the number of valence electrons and electron configuration for the following elements. The first one has been done for you.
▶️Answer/Explanation
Ans: 
The following chart shows the melting and boiling points of the first 20 elements of the periodic table.
Question:
Examine the graph and describe the pattern in melting points as you move from left to right across period 3 (from sodium to argon).
▶️Answer/Explanation
Ans: There is an increase in melting point of the first three metals (Na, Mg, Al) as the strength of metallic bonding increases; the sudden increase in melting point for silicon is due to the fact that this is a giant covalent structure with very high melting points and boiling points due to the strong covalent bonding; the large decrease in melting points of the final elements of period 3 is due to the fact that these elements (P, S, Cl, Ar) are simple molecular substances which are held together by weak intermolecular forces between the molecules.