Modern Model of the Atom

1
Chapter 4

• Modern Model of the Atom

2

• Electromagnetic Radiation form of energy that
  exhibits wavelike behavior as it travels through
  space
• Electromagnetic Spectrum all the forms of
  electromagnetic radiation

3
(No Transcript)
4
Question of the Day

• Why do our bodies tan?

5

• Wavelength (?) the distance between
  corresponding points on adjacent waves.
• Frequency (v) defined as the number of waves
  that pass a given point in a specific time

6
Photoelectric Effect

• Emission of electrons from a metal when light
  shines on the metal
• Quantum the minimum quantity of energy that can
  be lost or gained by an atom.

7

• Photon a particle of electromagnetic radiation
  having zero mass and carrying a quantum of energy.

8
(No Transcript)
9
(No Transcript)
10
Bohr Model of the Atom

• Electrons can only travel in special orbits at
  certain discrete, set distances from the nucleus
  with specific energies
• Electrons do not continuously lose energy as they
  travel, they only gain/lose energy by jumping
  from one allowed orbital to another.

11

• In the Bohr model, only certain orbits with
  certain radii are allowed orbits in between
  simply do not exist.
• When the electron is in one of these orbits, the
  atom has a fixed energy.
• The lowest energy state is closest to the
  nucleus.
• This orbit is separated from the nucleus by a
  large empty space where the electron simply
  cannot exist
• The energy of the electron is higher when it is
  in orbits that are farther from the nucleus

12
Explaining Spectral Lines

• An electron can move to a higher energy orbit by
  gaining an amount of energy equal to the distance
  between the two orbits.
• When the atom falls back from the excited state,
  the electron drops down to the lower energy
  orbit. In the process, light is emitted with an
  energy equal to the difference between the orbits.

13
Homework

• Page 97 1-5
• Due October 15

14
Bohrs Model

• In Bohrs model, electrons can jump from one
  allowed energy level to another but they can
  never have any energy between the allowed ones.

15
(No Transcript)
16

• Orbits (shells) get larger as the quantum number
  increases
• Electrons in the n 1 orbit have the lowest
  energy
• Each shell can hold a maximum of 2n2 electrons
• When an atom is being built, innermost shell is
  filled first. Aufbau Principle

17
(No Transcript)
18
Valence Shell

• The outermost occupied shell of an atom is called
  the valence shell

19
Valence Shell
20
Shortcut Method

• For the representative elements, the number of
  electrons in the valence shell of an atom is
  equal to the roman-numeral group number.

21
(No Transcript)
22
(No Transcript)
23

• s block is 2 elements wide because an s subshell
  can hold a maximum of 2 electrons
• p block is 6 elements wide because..
• d block is 10 elements wide

24

• The period (row) number tells you which shell (n)
  is currently being filled unless you are in the d
  or f block.
• In the d block, the value of n for the d subshell
  being filled is one less than the period number
• In the f block, the value is two less than the
  period number

25
Heisenberg Uncertainty Principle

• Electrons are detected by their interaction with
  photons
• Any attempt to locate an electron with a photon
  knocks the electron off its course
• As a result, there is always a basic uncertainty
  in trying to locate an electron

26
Heisenberg

• States that it is impossible to determine
  simultaneously both the position and velocity of
  an electron.

27
(No Transcript)
28
Orbitals

• Three dimensional areas around the nucleus that
  indicate the probable location of an electron

29
(No Transcript)