chemistry(electrons in atoms)

I - Background Information

What is light?

Light is radiant energy that travels in the form of electromagnetic waves.

How is light usually understood?

Light is usually understood as being a wave.

What characterizes light?

Light is characterized by wavelength or energy.

Parts of the electromagnetic spectrum

radio waves, microwaves, infrared light, visible light, ultraviolet light, X-rays, and gamma rays

Planck's hypothesis

Quantum hypothesis: the idea that light energy is contained in discrete packets called quanta

Planck's constant

6.626 x 10^-34 Js

How do we think of light (all radiant energy) as having?

a dual nature

Dual nature of matter

Matter exhibits both particle and wave properties.

Heisenberg uncertainty principle

the position and the momentum of a moving object cannot be simotaneously known or measured exactly

(the more you know about one, the less you know about the other)

II - Bohr Model

atomic emission spectra

the set of frequencies of the electromagnetic waves emitted by atoms of the element

what did Bohr oberve

the atomic emission spectra (a spectrum showing only certain discrete wavelengths)

what did Bohr explain and introduce

the lines in the spectra by introducing the idea of quantized energy levels for electrons

how are the lines in the spectra explained

by electron transitions from higher energy levels to lower energy levels

what did Bohr suggest about the movement of electrons

electrons move in definite orbits

was Bohr model accurate

no - fixed orbits dont work (heisenberg uncertainty principle)

III - Quantum Model

Quantum mechanical model

explains that properties of atoms by treating the electron as a wave and quantzing its energy

general ideas of quantum mechanics

-quantized enery levels

• position of electron given in probabilities

• electron is treated as a wave

• mathematically complex

Types of orbitals and their shapes and electron #

S sublevel

1 orbital, 2 electrons, sphere shaped

p sublevel

3 orbitals, 6 electrons, dumbbell shape

d sublevel

5 orbitals, 10 electrons, complicated shapes

f sublevel

7 orbitals, 14 electrons, even more complicated shapes

Aufbau Principle

electrons tend to populate the lower energy orbitals first… orbitals are filled according to increasing energy

Pauli Exclusion Principle

if 2 electrons are to be in the same orbital, they must have opposite spins

Hund's Rule

if electrons are to populate a given sublevel, they will do so in such a way that unpaired spins are maximized (seats on the bus/monopoly)

Terms

ground state

The lowest energy state of an atom

excited state

A state in which an atom has a higher potential energy than it has in its ground state

orbital

a region of probable locations for 2 electrons (region in space where electron with a particular energy is likely to be found)

energy level

a set of all sublevels having identical principal quantum numbers (n)

sublevel

a set of similar orbitals (same letter)

principal energy levels

the main energy levels of an atom

electron density

the density of an electron cloud

quantum number

number designating a principal energy level in an atom

electric spin

the clockwise or counterclockwise motion of an electron

Electron Configuration

the arrangement of electrons in the orbitals of an atom

valence electrons

Electrons on the outermost energy level of an atom