Chem LO's Exam 1

2 postulates of matter

1. matter is particulate(anything that has mass or takes up space)

2. The structure of the particles determines the property of matter

level of matter classification

1. State(solid liquid gas)

2. Composition(pure substance or mixture)

Pure substance

Any element(H) or compound(H20)

2 types of mixtures

1. Heterogeneous(a not evenly dispersed mixture like stew)

2. Homogeneous(an evenly dispersed mixture like tea)

Hypothesis

Explains an observation or makes a prediction about how a system will operate

Scientific law

A brief statement summarizing observations and indisputable facts

Theory

Explains why a system works

Ex. All matter is made of tiny, indestructible particles called atoms

Law of the conservation of mass

Matter is neither created nor destroyed

Law of definite proportions

A specific compound always contains the exact same elements in the exact same proportions by mass, no matter where it comes from.

Ex. H20 will always have an atomic mass ratio of 1:8 H:O

Law of multiple proportions

When 2 elements (A B) form 2 different compounds, the masses of element B that combine with 1 g of element A can be expressed as a ratio of small whole numbers

CO2 and CO. With 1 gram of C in each compound, CO2 would have 2.67 g of O, and CO would have 1.33 g of O. 2.67/1.33=2. A small whole number that explains the ratio of O in both elements

Dalton’s atomic theory of mass(4 points)

1. Each element is composed of atoms

2. All atoms of a given element have the same mass and other properties

3. Atoms combine in simple, whole-number ratios

4. Atoms of one element cannot change into atoms of another element

JJ Thomson

• Discovered the electron

• Charge-to-mass ratio of the electron

• Cathode rays experiment

• Plum Pudding model

Millikan

Oil drop experiment to discover the charge of an electron

Rutherford

• Gold foil experiment

• Rationalized that there must be a positive charge in the atom

• Accidentally discovered nucleus

Nuclear theory

1. Most of the mass of an atom and all of its positive charge is in the nucleus

2. The nucleus has most of the volume in an atom

3. Electrically neutral atoms have the same number of protons and electrons

• There are also neutrons, which hold mass

• Rutherford

Isotope

A version of an element on the periodic table with more mass because it has more neutrons

Atomic number

Number of protons

Defines the element

Mass number

All protons+ all neutrons

Ions

When neutral atoms gain or lose electrons

1. cations

2. anions

Cations

When an atom loses electrons, giving it a positive charge

Anion

When an atom gains an electron, giving it a negative charge

Isotope: natural abundance

The relative percentage of a specific isotope of a chemical element as it naturally occurs on Earth

Atomic mass

The weighted average of an elements naturally occurring isotopes

Go do a Natural Abundance question

Did you do it? Good.

What is the acronym for the table in LO 8

Taylor God Massive karma despite clowns misusing music, not pretty

4 rules of sigfigs

1. All non-zero digits are significant (123, 3 sigfigs)

2. All sandwiched zero’s are significant (103, 3 sigfigs)

3. All leading zero’s are NOT significant (0.0000001, 1 sigfig)

4. Trailing zero’s

   1. If it occurs after the dp, it is significant(11.301, 5 sigfigs)

   2. If it occurs before a dp, it is significant(1200.32, 6 sigfigs)

      1. If no zero, it is ambiguous, so put it into scientific notation

Addition and subtraction with sigfigs

Use the least amount of sigfigs after the dp as possible according to the factors you used in the equation

Multiplication and division with sigfigs

Use the smallest number of sigfigs a factor in the equation offers in your answer

Intensive property

Property of a substance that does NOT depend on the quantity of the substance

ex. Density

Extensive properties

Properties of a substance that do depend on quantity of substance

ex. Mass and volume

Positive change in energy

Energy is transferred from the surroundings into a system(endothermic)

Negative change in energy

Energy is transferred from a system to the surroundings(exothermic)

Exothermic

Heat is transferred from the system to the surroundings, making the system cooler

Gas to liquid to solid

ex. freezing, condensation, combustion

Endothermic

Heat is transferred from the surroundings to the system, making the system hotter

Solid to liquid to gas

ex. melting

Kinetic energy

The energy of motion

Potential energy

The energy of position or composition

Systems tend to try and change in ways that lower their potential energy

ex. if a 10kg weight is at the top of a building, it has gravitational potential energy and if you push it off, it becomes kinetic energy

Go do like 5 dimensional analysis problems right now.

Did you do them? All 5? Good.

Go do like 3 molar mass dimensional analysis problems. Go.

Did you do it? Did you get them all right? Good.

Speed of light

C, 3.00×10^8 m/s

Electromagnetic spectrum

(high)Gamma rays, x-rays, ultraviolet radiation, violet light, red light, infrared radiation, microwaves, radio waves(low)

Constructive interference

2 waves are in phase and form one big wave

• makes bright spots on film

Destructive interference

2 waves are out of phase and cancel out

• makes dark spots on film

What influences amplitude?

Brightness

What influences wavelength/frequency?

Color

Frequency

Number of cycles of the wave that passes by you in a given amount of time

Diffraction and diffraction pattern on film

• Proof of light acting like a wave

The bending and spreading of waves when the pass through a narrow opening or around an obstacle
Pattern: bright spot in the center, interference pattern on the rest of the film

The uncertainty principle

You cannot simultaneously know the position and velocity of an electron because they are complementary properties

Indeterminancy

It is impossible to know the path of the electron because we cannot know the position AND velocity of it

Probability distribution map

Shows how likely it is that an electron will be found in a particular volume

Orbital

Where an electron is most likely to be found when modeled as a standing wave around the nucleus
Designated by 3 quantum numbers: principle(n) angular momentum(l) magnetic(msubl)

atomic orbitals

Orbitals with the same n value are in the same shell/principle level
Orbitals with the same n and l are in the same subshell/sublevel
The first 3 quantum numbers specifiy a single orbital within an atom

Nodes

Distance within an orbital where the probability of finding an electron drops off only to increase again
Depends on principle quantum number

Principle quantum number (n)

Definition: size of the orbital

How to find: look at the highest number before an S orbital

Cannot be 0

Higher the value of n, the higher the energy of the orbital

Angular momentum quantum number (l)

Definition: shape of orbital

How to find: look at the last letter listed in the electron configuration or 0, n-1. s=0, p=1, d=2, f=3

magnetic quantum number (msubl)

Definition: possible orientation of the orbital

How to find: take the l value and its anything from that number negative to that number positive

ex. l=2, msubl= -2, -1, 0, 1, or 2 no matter what

Possible orientations; s=1, p=3, d=5, f=7

Spin quantum number (msubs)

Possible values are -/+ 1/2, only 2 fit in each orbital and they must be different

Quantum mechanic model characteristics

• 3d

• electrons don’t obey physics

• electrons are located in an orbital

• you can only know the position or the velocity

Bohr model

• 2d

• electron obeys physics

• electron travels in a circular orbit around the nucleus analogous with planetary movement

• position and velocity of the electron are known

Electron configuration

Definition: how many electrons are occupying each subshell for an atom

ex. 1s², 1= principal qn, s= subshell, 2= #of orbital electrons

Orbital diagram

Shows how electrons occupy degenerate orbitals in the same subshell(arrows)

Pauli exclusion principle

No 2 electrons in the same atom can have the same 4 quantum numbers

Aufbau principle

We can build electron configuration for multi-electron atoms by putting their electron in the lowest energy orbital available

Hunds rule

You must fill degenerate orbitals singly first with parralle spins before adding the opposite spins to the beginning of the orbital

Special transition+inner transition metals

Cu= 4s^1 3d^10
Ag= 5s^1 4d^10

Cr= 4s^1 3d^5
Mo= 5s^1 4d^5

Sublevel splitting

Coulumbs law, Shielding effect, penetration effect

Coulumb’s law

Opposite charges attract, like charges repel

Shielding effect

reduces the net positive charge an electron experiences from the nucleus

ex. if there are 2 electrons(negative) by the nucleus(positive) a third electron will be more repelled by the 2 electrons than will be attracted by the nucleus

Penetration effect

Reduces shielding effect due to an overlap in orbitals(s blocks p, p blocks d, d blocks f)

Degenerate orbitals

When all orbitals have the same energy, also develops sublevel splitting

Column 8A on the periodic table

Nobel gasses
Stable because of fully filled s and p subshells for their outermost shell

1A

Alkali metals

Characteristics:

• highly reactive

• lose 1 electron when forming an ionic compound because there is 1 electron in the outermost s subshell

• forms a 1+ ion

2A

Alkaline earth metals

Characteristics:

• Slightly less reactive

• Tend to lose 2 electrons when they react because 2 electrons are in the outermost subshell

• forms a 2+ ion

7A

Halogens

Characteristics

• Tend to accept 1 electron when formic an ionic compound because there are 5 in the outer p subshell

• Also could share an electron to form a covalent bond

• 1- ion

6A

• Forms a 2- ion because it needs 2 electrons to look like it’s nearest nobel gas

Metal characteristics

• Malleable(can be hammered into sheets)

• Ductile(pulled into wires)

• Shiny

• Solid at room temperature

• Good conductors of heat and electricity

• Tend to lose electrons in reactions to gain a more stable configuration

Non-metal characteristics

• Poor conductors of heat and electricity

• Gain or share electrons in reactions to gain a more stable configuration

Divided periodic table