Graphite and diamond are both made of carbon, but only one is ...

[Jkov05]

Graphite and diamond are both made of carbon, but only one is good for pencil lead. Why is graphite
  useful for this task while diamond is not? What will be an ideal response?

Question 2

What is the main feature of metallic bonding, and what properties result from this main feature? What will be an ideal response?

[kishoreddi]

Answer to Question 1

The carbon atoms in diamond are held together by covalent bonds; they share electrons so that each
carbon atom has the noble gas configuration of eight electrons in its outermost electron shell. Diamond
is very strong. The carbon atoms in graphite are covalently bonded to form sheets, so the sheets are
internally strong but are held together by weak van der Waals bonds. Small pieces of graphite can
flake off along planes when a pencil is run across a piece of paper.

Answer to Question 2

In metals, electrons in the outermost electron shells can move freely from one atom to another. The
movement of electrons accounts for the metals metallic luster, electrical and thermal conductivity, and
ease of reshaping.

[Jkov05]

Great answer, keep it coming

[emsimon14]

Excellent