The bond between silicon and germanium is

Analyze the question: The question asks what type of bond holds atoms together in silicon and germanium. These are the two classic semiconductor elements from Physics (Electronics/Conduction in Solids).

Explain the concept:

• Silicon (Si) and germanium (Ge) are both Group IV elements, so each atom has 4 valence electrons.
• Each atom needs 8 electrons in its outer shell to be stable.
• To achieve this, each atom shares one electron with each of its 4 neighbouring atoms. This sharing of electron pairs is a covalent bond.
• The result is a regular crystal lattice (diamond-type structure) in which every atom is joined to four others.

Check the options:

• A. Dative: This is a covalent bond where both shared electrons come from one atom (e.g. in NH₄⁺). It doesn't apply here, because each atom contributes its own electron.
• B. Covalent bond: Correct. Neighbouring atoms share valence electrons.
• C. Trivalent: This describes an element with a valency of 3 (such as boron or aluminium, used as acceptor impurities). It is not a type of bond.
• D. Ionic: This involves the transfer of electrons between a metal and a non-metal. Si and Ge are not like that, so it does not apply.

Answer: The bond in silicon and germanium crystals is a covalent bond, which is option B.

Exam tip: Remember "Group IV = 4 valence electrons = share, not transfer." Whenever you see Si, Ge or carbon (diamond) in a pure crystal, think covalent. Also note that "trivalent" and "pentavalent" show up in doping questions (e.g. boron is trivalent and gives p-type, phosphorus is pentavalent and gives n-type). They are not bond types.