Atomic Structure and Periodicity

Confused??? You’ve Got Company!

“No familiar conceptions can be woven around the

electron; something unknown is doing we don’t

know what.”

Physicist Sir Arthur Eddington

The Nature of the Physical World1934

The Wave-like Electron

Louis deBroglie

The electron propagates through space as an

energy wave. To understand the atom, one must understand

the behavior of electromagnetic waves.

Wave-Particle DualityJJ Thomson won the Nobel prize for describing the electron as a particle.His son, George Thomson won the Nobel prize for describing the wave-like nature of the electron.

The electron

is a particle!

The electron is an energy

wave!

c = C = speed of light, a constant (3.00 x 108 m/s)

= frequency, in units of hertz (hz, sec-1) = wavelength, in meters

Electromagnetic radiation propagates through space as a wave moving at the speed of light.

The Wave Like Electron

Types of electromagnetic radiation:

The Wave Like Electron

Long Wavelength

=Low Frequency

=Low ENERGY

Short Wavelength

=High Frequency

=High ENERGY

Wavelength Table

…produces all of the colors in a continuous spectrum

Spectroscopic analysis of the visible spectrum…

…produces a “bright line” spectrum

Spectroscopic analysis of the hydrogen spectrum…

This produces bandsof light with definitewavelengths.

Electron transitionsinvolve jumps of definite amounts ofenergy.

Niels Bohr

Proposed that the electron in a hydrogen atom moves around the nucleus only in certainallowed circular orbits.

E = h

E = Energy, in units of Joules (kg·m2/s2)

h = Planck’s constant (6.626 x 10-34 J·s)

= frequency, in units of hertz (hz, sec-1)

The energy (E ) of electromagnetic radiation is directly proportional to the frequency () of the radiation.

Relating Frequency, Wavelength and Energy

c hE

hcE

Common re-arrangements:

Ehc

Electron Energy in Hydrogen

***Equation works only for atoms or ions with 1 electron (H, He+, Li2+, etc).

n = energy level

218 110178.2

nJxEelectron

Calculating Energy Change, E, for

Electron Transitions

Energy must be absorbed from a photon (+E) to move an electron away from the nucleusEnergy (a photon) must be given off (-E) when an electron moves toward the nucleus

2218 1110178.2

initialfinal nnJxE

Orbital filling table

Electron configuration of the elements of the first three

series

Element Configuration notation

Orbital notation Noble gas notation

Lithium 1s22s1 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s1

Beryllium 1s22s2 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2

Boron 1s22s2p1 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p1

Carbon 1s22s2p2 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p2

Nitrogen 1s22s2p3 ____ ____ ____ ____ ____

1s 2s 2p

[He]2s2p3

Oxygen 1s22s2p4 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p4

Fluorine 1s22s2p5 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p5

Neon 1s22s2p6 ____ ____ ____ ____ ____ 1s 2s 2p

[He]2s2p6

Irregular confirmations of Cr and CuChromium steals a 4s electron to halffill its 3d sublevel

Copper steals a 4s electron to FILL its 3d sublevel

ISOELECTRONIC SUBSTANCES and EXCITED STATES

• Substances with the same number of electrons are isoelectronic ions.

• Isoelectronic ions (or molecules) ions (or molecules) with the same number of valence electrons.

• Isoelectronic substances: P3, S2, Cl, Ar, K+, Ca2+.

• The electron configation of an element in an excited state will have an electron in a high-energy state E.g. [Ar]4s13d94p1 is an excited-state electron configuration for Cu.

Orbitals of the same shape (s, for instance) grow larger as n increases…

Nodes are regions of low probability within an orbital.

Sizes of s orbitals

The s orbital has a spherical shape centered aroundthe origin of the three axes in space.

s orbital shape

There are three dumbbell-shaped p orbitals in each energy level above n = 1, each assigned to its own axis (x, y and z) in space.

P orbital shape

Things get a bit more complicated with the five d orbitals that are found in the d sublevels beginning with n = 3. To remember the shapes, think of:

…and a “dumbell with a donut”!

“double dumbells”

Shape of f orbitals