Chemistry Unit 2

A Scientific Law

summary of what is seen in observations

A Scientific Theory

explanation of why these observations are occurring

Atomic Theory

Explains why all matter acts as it does because it is composed of atoms

Democritus

Developed Atomic theory, and thought matter could not be divided infinitely

Compound

Pure substances that could be broken down into smaller substances

Element

Pure substances that couldn't be broken down

Law of Conservation of Mass

chemical reaction does not change the mass of the matter present and the mass of the reactants is equal to the mass of the products

Law of definite proportions

All pure compounds have exactly the same proportions by mass of elements regardless of size

Dalton

Found that gases acted as though they were made of solid microscopic particles, all elements are made of atoms, atoms of the same element are exactly alike, atoms of different elements are different, compounds are formed by joining two or more elements

Law of Multiple Proportions

AKA Dalton's law: The same elements may combine differently to form different compounds, Atoms may join together in different manners.

Thomson

-Found negative particles could come from neutral elements
-Atom is made of smaller things (+ and -), and is divisible
-Successfully separated negative particles (electrons) but could not separate the positive particle (protons)
-"Plum pudding model" negative particles floating in a positively charged gel like material

Rutherford

-Fired protons at a sheet of gold foil most went through unaffected, some bounced away
-There is a small dense area of positive particles at the center of the atom- the nucleus
-Electrons are scattered near the outside of the atom with mostly empty space between the nucleus and the electrons

Bohr

electrons move in definite orbits around the nucleus, these orbits or energy levels are located at certain distances from the nucleus

Wave Model(Present Day)

-Based on complex math equations
-Orbits are more complex than originally thought
-de Broglie stated that electrons (particles) have wave properties, and he viewed these as standing waves, like those produce when a guitar string is plucked (classical physics.)
-Schrodinger assumed that the electron in Hydrogen behaves as a standing wave
-When Schrodinger's equation is analyzed, many solutions are found
-Each solution represents an atomic orbital
-An atomic orbital is the most probable location for finding an electron

Heisenberg Uncertainty Principle

-The more accurately we know the particle's position, the less accurately we can know it momentum and vice versa
-We can't know the exact motion of the electron around the nucleus
-The area that an electron orbits is called an "electron cloud"

Protons

positive, in the nucleus, p+, 1 amu

neutrons

neutral, in the nucleus, n^o, 1 amu

electrons

negative, in the electron cloud or shell, e-, 0.0006 amu

Ions

Charged particles

atomic mass =

protons + neutrons

number of neutrons =

mass number - atomic number

Isotope

Atoms of the same element with a different number of neutrons

protons(cannot change for an element) =

atomic number

electrons(if atom is neutral) =

protons

Gravity

universal attraction of all objects to one another

Electromagnetism

Attraction or repulsion based on charge or poles

Strong Nuclear Force

Force holding the nucleus of an atom together

Weak Nuclear Force

Force causing subatomic particles to change into one another (causing nuclear radiation)

Quantum mechanics

how forces and motion work at an atomic level, Energy only comes out of an atom in discrete amounts(specific numerical amounts- little chunks)

Bohr(energy levels)

-Determined electrons were at certain energy levels from the nucleus.
-Excited e- 's jump to higher energy levels, then fall back to ground.
-Since the distance it "falls" back is always the same, energy always comes out of an atom in discrete amounts.
-The energy level are the numbers on the left column

What keeps electrons near?

electromagnetic force

Pauli Exclusion Principle

You can not have more than two electrons in one orbital (on the same line) because of this repulsion

Orbitals not orbits

With simple orbits electrons would be pulled into the nucleus-an orbital is just the area with the highest probability of finding an electron

Lowest energy level

s, sphere

first energy level

hold 1 s orbital

second energy level

hold 1 s orbital and 3 p orbitals(p orbital is a higher energy shape than s)

third energy level

hold 1 s orbital 3 p orbitals and 5 d orbitals

The more positive the nucleus...

the closer the electrons can be pulled in

Aufbau Principle

electrons will occupy the lowest energy orbital available

Without neutrons

atom will break apart(radioactive decay)

1 mole =

6.022x10^23 particles(Avogadro's number)

Disinfection of water

Chlorine, Iodine, UV sterilization

Causes harm to water

Bacteria and microorganisms

Distillation

Heat water, water vapor rises leaving behind solid things dissolved. The water is vapor is condensed

Reverse Osmosis

Water is forced through a semipermeable membrane by applying a pressure greater than the osmotic pressure

Activated Charcoal Filtration

The charcoal has large pores that several materials get absorbed in and then are easily filtered out