8/14/2019 Unit 2 Study Guide Chemistry

1/4

Unit 2 Study Guide2.1 Emergence of Atoms

Law of Conservation of Mass - Mass is never lost or gained during a chemical and physicalchange. If you have a open experiment, mass can be lost as gas and escape. But if you have aclosed experiment, you will keep all the mass.

Law of Definite Proportions - Chemical compound contains same elements in same proportions by mass regardless of size per sample

Law of Multiple Proportions - If 2 or more compounds have the same elements then the ratio of the masses of the 2 nd element combined with the 1 st element is the ratio of small whole numbers.

Ex. 2.66 oxygen 1 carbon

1.33 g oxygen 1 carbon

Ratio is 2:1

Mass Ratio is ratio of one element to another in a compound.

1. All elements composed of small particles called atomsa. Law of conservation of mass

2. Atoms of a given element have the same size, mass, and properties. Atoms of differentelements have different properties.

a. Law of Definite and Multiple Proportions.i. Same elements have the same mass

3. Atoms cannot be broken down

a. Law of Definite and Multiple Proportions4. Atoms combine to form compoundsa. Law of Definite and Multiple Proportions

5. Atoms can be combined, separated, or rearranged in chemical reactionsa. All Laws

Daltons Atomic Theory

1. All elements are composed of extremely small particles called atoms.a. Now we know there are smaller particles WITHIN atoms called corks ect

2. Atoms of a given element are identical in size, mass, and other properties; atoms of different elements differ in size, mass, and other properties.

a. True3. Atoms cannot be subdivided, created, or destroyed.a. Now we can do that to make bombs

4. Atoms of different elements combine in simple whole-number ratios to form chemicalcompounds.

a. True5. In chemical reactions, atoms are combined, separated, or rearranged

a. True

8/14/2019 Unit 2 Study Guide Chemistry

2/4

Thompsons cathode ray tube

Cathode rays were deflected when a negative charge was put near it. This showed that electronswere negatively charged.

Plum Pudding Model

A sphere with a positively charged pudding. Had negatively charged electrons randomlydispersed throughout the pudding.

Rutherfords Gold Foil Experiment

Alpha particles were shot at gold foil. Almost always went through, but very rarely reflected and bounced off. This led to the discovery of the very small nucleus within an atom. This was positively charged because when the two positively particles collided, the beam bounced off.This led to the discovery that there was a dense and small nucleus and the electrons were spreadaround it.

Robert Millikans Oil Drop Experiment

He had oil drops get pulled by a known gravitational force. He also had a magnetic field pushingthe oil drop upward. When the oil drop was levitating in mid air he knew the magnetic force andgravitational pull were equal. He then was able to solve for the charge of the electron.

2.2 Subatomic Particles and Isotopes

Rutherford found through his gold foil experiment that there was a dense positively chargednucleus. Thompson found out that there were negatively charged particles that revolved around

the nucleus.The placement of the electrons of an element can be used to identify a number of different

properties including the number of orbitals, the energy level, and the atomic number.

Neutrons - They are place holders so the positively charged protons dont touch each other and bounce off. Hold the nucleus together.

Atomic Number - the number of protons of a given element. Atomic Mass is the mass of the atom.Atomic mass atomic number is the number of neutrons.

Isotope - atoms of same element with different number of neutrons. The atomic mass on the periodic table is affected by the isotopes because it is an AVERAGE of the naturally occurringisotopes. Thats why its normally a decimal.

A weighted average means rather than all the data contributing equally to the final average, somedata points contribute more than others.

Ex.

8/14/2019 Unit 2 Study Guide Chemistry

3/4

The percent abundance for chlorine-35 is 75.53% . The percent abundance for chlorine-37is 24.4%. The mass for Cl-35 is 35.0 amu and for Cl-37 it is 37.0 amu.

2.3 The nature of light, niels bohr, and quantum mechanics

Waveparticle duality -the concept that all energy (and thus all matter ) exhibits both wave -likeand particle -like properties

Different Types of Electromagnetic Energy

In wave form:

x rays ultraviolet light infrared light microwaves Radiowaves

The difference of the wave forms depends of the frequencies of wavelengths.

Shorter wavelength and faster frequency correspond to higher energy levels. Visa Versa.

In order of where they lie on the spectrum from least the greatest

Radio waves

microwaves infrared light ultraviolet light x rays

Black Body Radiation - Where solid or liquid is heated and emits light. Like a toaster getting redfrom being so hot.

Planks Constant - **** The energy increased between each level change?

The color of the photon depends on how much energy is released, which depends on the

frequency (of my tits)

Photoelectric effect- light shone on metal and electrons were produced. Strength of light had noeffect but the rate at which they were released had an effect. So good

http://en.wikipedia.org/wiki/Energyhttp://en.wikipedia.org/wiki/Matterhttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Subatomic_particlehttp://en.wikipedia.org/wiki/Matterhttp://en.wikipedia.org/wiki/Wavehttp://en.wikipedia.org/wiki/Subatomic_particlehttp://en.wikipedia.org/wiki/Energy

8/14/2019 Unit 2 Study Guide Chemistry

4/4

we have l=h/mv where mv is mass times velocity which is equal to momentum. This allows usto calculate the wavelength of a particle in motion., weird l thing is equal to wavelength and h is

planks constant

white light- combination of all colors

colored light- specific light on the spectrum

black absorbs light, white reflects

the atoms electrons have their own unique frequency, giving off a different color of light or energy

Bohr realized thatwhen energy was added the electron became excited and when the energy wasreleased so was a photon

Different orbitals in Bohr model, logic is that there are specific orbitals for each electron

Ground state- lowest energy state of atom

Excited state- higher than ground state

There is a different emission line spectrum for each element because they have unique numbersof electrons and different energies

Each element has its own specific spectrum, so an element can be identified by the spectrum, ex.Fingerprint

2.4 Electron configurations

Bohrs model is simplified because now we know the different shapes of each orbital, which arenot always in an oval

Maximum number of electrons per energy level is 2n 2 where n is the energy level

Hunds Rule- electrons would rather be alone if another equal energy orbital is available

Aufbau Principle- electrons go to the lowest energy orbital first

Pauli Exclusion Principle- every orbital can hold 2 electrons if they have opposite spins

Higher atomic number means more potential energy