Question

May be slight error due to rouriaing) 6. Briefly describe how the energy bands are formed when atoms form a crystal (start from what energy an electron can have in an atom). What model is used to mathematically demonstrate the formation of energy bands in solids? (7 pts)

Answer 1

Formation of Energy bande in soliels: Energy of an Election : IN > otom - No. of electrons in an orbit can be calculated by the formula ano Whele n- no.of orbit ( shell number) Example: If ned them noof elecerond in the second orbit is equal to any = 2(2)? = 8. elections -> Energy of an election can be calculated by E = -13.67 EV khele z is the atomic number one no. of shello of the n 1 (inere afrk) = E 1 (inerea, deo) - Suppose there are two Energief manned E, & Eq. £1 = -3.6/1"), E2 =-13.00 ) if both Enchgrep have some atomic number 71 = 22 (same členure) & n = n2 - We thought thought that Z1 = Z2 & nong then EiE, But mal in a Crystal we'll have ELF E2 (Even if 22.& nin2). This is because of forces of attrachan of election in crystal. some shell in a caust in actual

Inter atomic forenfe of an atom differ by it's position. A note This ctor hane high interarorulus This atom have left interctornie - forces. - Elections of different atoms in the crystal that are in same orbit (Whele z& nalte same) have very close Energy difference. So they form band of Energy having Energies very closely. → Interactions forces between the closely packed atoms in, the crystal even the electrons in the some orbito of different atoms of the crystal have different Energier Because of the energy levels sporold up, all the Energy bando alle formed. Energy band diagram a conduction band → Electrons en valence band EgIT Forbidden band gain the required Energy to o Ivalence band the conduction band. Eg - Energy gap which is also called as forbidden Energy gap. → According to Neil Bcho's theory of atomic structure structure, all the ators have discrete Energy levels clound central nudeus. These deserete Energy lende further transformed into Energy band structure in the solad type structures. participate in conduction in