Ch.4

Electrons

Energy as Waves

• Light (one form of energy) travels through space in a wavelike behavior

• Other forms of energy also have wave characteristics (electromagnetic spectrum) p. 98

• The more energy, the faster the wave moves, the shorter the wavelength – p.98

Electromagnetic Spectrum

Wavelength & Frequency

Electrons as Waves• Each element has a set number of

subatomic particles

• Those particles (electrons) can be excited by extra energy and emit a color

• Each element has a different set number of electrons thus, having a different color emitted

• This color is an identifying characteristic of the element p.101

Table 2 p.110

Electron Emission Spectrum

Background Information

• De Broglie set out to prove that electrons acted as particles and waves in 1924 – found that electrons existed as waves in a small space which is also like a particle

• Heisenberg made a conclusion in 1927, that it is impossible to calculate the position and velocity of an electron at the same time

Additional Background• Schrodinger developed the quantum

theory and four quantum numbers (that are letters) to explain his theory –n,l,m,s

• Summary of quantum numbers –Table 2 -- p.110

• Remember: s – holds 2e- p – holds 6e-

d – holds 10e-f – holds 14e-

orbitals can only hold 2e- each, each sublevel has an orbital count of half its e-

Electron Configuration

• A systematic way of placing all of the electrons of an atom into their energy level, sublevel, and correct spin

• Connects to the periodic table into repeating trends and characteristics of metals, nonmetals, and metalloids

Rules to Follow

• Aufbau principle – an electron occupies the lowest-energy level first

• Pauli exclusion principle – two electrons in the same orbital must have opposite spins

• Hund’s rule – all electrons must singly occupy orbitals of the same spin before adding another electron of opposite spin – p.112

Orbital Notation

• Notates electrons represented as arrows in opposite spins in its orbital that is represented by an underline or a box

• Let’s practice!!p.113 (1 & 2)

• Electron-Configuration NotationElectron-Configuration Notation – eliminates the arrows and lines and represents the electrons by superscripts

• Let’s practice!!

p.121 (1-5)

Orbital Diagrams

Noble Gas Notation

• Used as a short hand method of finding the electron configuration

• Used for higher atomic numbers • Place the noble gas before the atom

in question in brackets• Start at the next energy level and

add electrons from the noble to the total amount of electrons as normal

• Example: [Kr]5s1

Lewis Dot Diagram

• Once the valence electrons are established, either by electron configuration or position of periodic table, only those electrons are used in bonding.

• Those electrons are notated by representing them as dots around the element symbol

• Example: Ar has 18 electrons what does the electron dot diagram look like?

Oxidation Numbers p.232• Basically, charges depicting the number of

electrons that are lost or gained • Can be determined by the number of

electrons needed to fill orbitals to make them complete or the number of electrons transferred to get to a level that has full orbitals

• Because all groups on the periodic table have the same valence electrons, the position of the element tells the oxidation number

• Example: H+1 or H1+

Ch. 5 Periodic Law

History of Periodic Table

• Credit for the first periodic table goes to Russian scientist Dmitri Mendeleev that was published in 1869.

• Mendeleev arranged the periodic table in order of increasing atomic mass.

• In 1911, Henry Moseley rearranged the periodic table in order of increasing atomic numbers which made more of a connection. Also known for periodic law.

Some Elements Mendeleev Predicted

Electron Configuration & The Periodic Table (pp. 138-139)

• The periodic table has been divided into 4 blocks that represent the s,p,d, & f sublevels of electron configuration.

• The ending configuration (last part of configuration) is used to locate the desired element.

• One is added to the ending configuration for d-block to find its location on the periodic table.

• Two is added to the ending configuration for f-block to find its location on the periodic table.

Periodic Trends Definitions

• Atomic Radius – def: one-half the distance between the nuclei of two identical atoms that are bonded together

• Electronegativity – def: a measure of the ability of an atom in a chemical compound to attract electrons from another atom in the compound

• Ionization energy – def: the energy required to remove one electron from a neutral atom of an element

Periodic Trends