UNIT 3 ELECTRON

CONFIGURATIONSPart B

Bohr’s Model of Hydrogen

WHAT HAVE WE LEARNED SO FAR?

Discharging Tubes

The Flame Test The light coming out of the excited atomic

entities is very specific to particular element!Results are quite

reproducible.

ELECTROMAGNETIC RADIATIONS (LIGHTS) COMING OUT OR BEING ABSORBED BY ATOMS INDICATE THAT THERE ARE VERY SPECIFIC ENERGY CHANGES WITHIN THE ATOMIC ENTITIES (ATOMS AND IONS).

NO NUCLEAR CHANGES HAVE EVER BEEN OBSERVED INDICATE THAT THE ENERGY CHANGES HAVE TO COME FROM ELECTRONS SURROUNDING THE NUCLEUS.

How Come?Classic Model: Electron anywhere it ‘wants’ to be

Problems with classic model:E moving through electric field will emit light & from the classic model, emitted light should have differing wavelengths

NIELS BOHR (1885 – 1962)

Increasing energy with greater distance from nucleus

BOHR’S MODEL OF HYDROGEN ATOM

Incr

easi

ng e

nerg

y

Nucleus

First-ground

Second

Third

Fourth

Fifth-excited}Further away

from the nucleus means more energy.

There is no “in between” energy

Energy Levels

quantum – quantity of energy gained or lost by an atom when electrons are excitedphoton – a quantum of lightground state – lowest energy level of an atomexcited state – a heightened state of energy in an atom

Electrons of hydrogen circle the nucleus in orbits 1. orbits have a fixed amount of energy in

the ground state. 2. orbits are a fixed distance from the

nucleus. 3. orbits furthest from the nucleus have the

greatest energy.

BOHR’S MODEL OF HYDROGEN ATOM

BOHR’S MODEL OF HYDROGEN ATOM

BOHR’S MODEL OF HYDROGEN ATOM

BOHR’S MODEL OF HYDROGEN ATOM

Bohr’s Model of Hydrogen Atom

Orbits Transitions of e between those orbits involve change in energyChange in energy (E(n2 –n1) has to be accounted for By photons

Successful in accounting for most of the H-1 emission/absorption spectral linesBUT only works for H-1