Unit 3 (History, Atomic Theory, and Electrons)

Chemistry

Democritus

Greek philosopher, first to propose that matter is indivisible, coined “atomos”, and was criticized by Aristotle

Dalton

English teacher in the early 1800’s, proposed the first modern atomic theory, and developed the solid sphere model

Thomson

British physicist in the late 1800’s, discovered the electron using a cathode ray tube, and developed the plum pudding model

Millikan

American physicist in the late 1800’s, determined the charge and mass of an electron via the oil drop experiment

Rutherford

British physicist in the late 1800’s and early 1900’s; determined that there is a small, dense, positive nucleus and the rest of the atom is mostly empty space via the gold foil experiment; and developed the nuclear model

Chadwick

British physicist in the early 1900’s, discovered the neutron via bombarding Beryllium with alpha particles.

De Broglie

He proposed that electrons are particles that also act like waves, electrons have a dual nature

Planck

Found that matter can absorb and release energy in specific amounts called quanta

Bohr

Danish physicist in the early 1900’s, developed the planetary model in which electrons circularly orbit the nucleus

Heisenberg Uncertainty Principle

It is impossible to know both the velocity and position of electrons at the same time

Erwin Schrodinger

Austrian-Irish physicist in the early to mid 1900’s, developed the cloud model in which electrons are shown in a path of probability

Electromagnetic Radiation/Waves

A type of energy that exhibits a wavelike behavior as it travels through space

Wavelength (λ)

Measured in meters from crest to crest or trough to trough (simplification for this class)

Frequency (ν)

Measured in Hz or s^-1 as the number of times a wavelength repeats during a given time

Amplititude (A)

The distance from the crest or trough to the origin (half the total height)

In c = λν, what is c?

2.998×10^8 m/s, the speed of light

The only differences between the forms of electromagnetic radiation

Frequencies and wavelengths

Quantum

The minimum amount of energy that can be gained or lost by an atom

What is h in E=hν?

6.626×10^-34 Js, Planck’s constant

Light has a dual nature

Light acts as both a wave and a particle

Photons

Massless particle that carries a quantum of energy, the particle of light

Atomic emission spectrum

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

Evidence of Planck’s idea of quanta

The Atomic Emission Spectrum, since it’s continuous for any element, has individual lines that correspond to frequencies emitted by atoms, and it’s unique for each element

Ground State

The lowest allowable energy state for an atom

Excited State

When an atom has at least a quanta of energy

When do atoms release energy?

When the electrons drop an energy level, when the atoms loses at least one quanta of energy

What type of energy do atoms release?

Electromagnetic radiation

λ = h/(mv)

De Broglie’s equation to the determine the wavelengths of electrons

Schrodinger’s Quantum Mechanical Model

Took into account De Broglie’s idea of electrons behaving like waves and Heisenberg’s Uncertainty Principle to determine an atom’s atomic orbital

Energy Levels (PEL)

Corresponds with the different periods on the periodic table

Sublevel

Within each PEL, they show a more precise location of the electrons and increase with energy level

Atomic orbital

A 3D region in which the electrons are most likely to be located. Each one has a unique shape based on its sublevel and its location within that sublevel

What do valence electrons determine?

Chemical properties for the element

Why are the noble gasses inert?

Because they have the strongest pull on their electrons out of their respective rows

What are the two liquid elements at room temp?

Mercury and Bromine

What are the 11 gaseous elements at room temp?

The noble gasses, Hydrogen, Nitrogen to Fluorine, and Chlorine

How are the elements organized on the Periodic Table?

By increasing atomic number

Which 7 elements form diatomic pairs?

Nitrogen to Fluorine, Fluorine to Iodine, and Hydrogen

Electronegativity

The ability of an atom to attract electrons when it is part of a chemical bond

Ionization Energy

The amount of energy required to remove electrons from an atom, an increasing amount for every electron taken

Atomic Radius

Half the distance between the nuclei of two identical atoms

Ionic Radius

The radius of an ion

A cation’s radius is…

…smaller than a neutral atom’s radius

An anion’s radius is…

…bigger than a neutral atom’s radius

What are the 5 properties of metals?

They’re good conductors, usually solid at room temp, malleable, ductile, and tend to lose electrons to form cations

What are the four properties of nonmetals?

They are poor conductors, usually solid or gaseous at room temp, brittle when solid, and tend to gain electrons to form anions

Aufbau Principle

Each electron occupies the lowest energy orbital available

Hund’s Rule

Each orbital in the same sublevel must hold at least one electron before electrons can pair up in the same orbital

Pauli Exclusion Principle

No more than two electrons can occupy the same orbital and electrons in the same orbital must spin in opposite directions