Bohr Model of the Atom (8, 9)

What is the three problems with Bohr's three postulates?

1) It is only valid for one-electron systems 2) he knew that electrons move in a circular orbit of radius, r, around a fixed nucleus. BUT he didn't know what kept it there

What was Bohr's three postulates?

1) the stationary energy state: atoms exist only in discrete energy states 2) the quantum jump: an atom undergoes transitions form one E state to another in sudden jumps (quantum leaps) 3) energy conservation: Atoms gain or lose E by absorbing or emitting photons of discrete energies; energy is conserved after it jumps. - only valid for one-electron systems

What force attracts electrons to the nucleus?

Coulombic force

What is the equation for the total energy change (or the energy of the nth state) for Niels Bohr's Planetary Model?

En = (-13.6 eV) * (z^2/n^2)

When an atom becomes more stable by relaxing down energy states, what does Eph equal?

Eph = -ΔEatom

When an atom becomes less stable by leaping up energy states, what does Eph equal?

Eph = ΔEatom

What does a bigger transition from one energy state to another mean for Eph?

Eph is greater • length of arrow is directly proportional to Eph

What did the Bohr Model of the Atom build upon?

Rutherford's Nuclear Model of the Atom

From what model did Bohr theory start from?

Rutherford's planetary model

For Bohr's model, what can you substitute in for PE in this equation: Etot = PE + KE?

V(r) since it is a coulombic interaction • also, KE = -1/2*V(r) and En = -KE

For the Bohr model, a definite r value exists for ________.

each state

What is the equation that related the v of the light absorbed and the initial and final energy states?

hv = Ef - Ei = ΔE ΔE > 0, absorption ΔE < 0, emission

What did Bohr's model explain?

it could predict the atomic spectra - he could calculate exactly wavelength of the photons that would be emitted or absorbed - proposed to account for discrete emissions spectrum of gaseous atoms

Fixed total E (En) of all the bound E states is positive or negative?

negative, and it varies with atomic # and quantum #.

What is the equation for the radius in the nth state for Niels Bohr's Planetary Model?

rn = (n^2/z) * ao

For bounds states, what is greater, |V(r)| or |KE|?

|V(r)| > |KE| • therefore, PE always dominates for bound states

Why did Bohr's Planetary model gain acceptance?

• it correctly predicted the energies of the lines in the H atom spectrum