Chem 1040 Midterm Review PDF

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Chem 1040 Midterm review Fall 2017 Sofia Lamarche Solids, Liquids and Gases -

Matter can be classified by its physical and chemical state

Solids: -

Gases: Rigid, incompressible, fixed shape and volume

Liquids: -

-

Fluid, compressible, no fixed shape or volume

Vapor: matter in gaseous form that's usually

Fluid, incompressible, fixed volume,

liquid or gas

no fixed shape

Significant Figures -

The last # when measures is uncertain

Rules: -

All non zero digits are significant

-

zeros after decimals are significant

-

✖ and

-

and

sig figs in answer = measurement with least # of sig figs sig figs don’t matter, # of decimal digits does. Answer should have the same

# of decimal digits as the measurement with the least # of decimals Exact Numbers: -

Counted #’s or defined units

-

No uncertainty therefore don’t affect sig figs

Rounding: -

If the final digit is 5≤ add round up and drop all other #’s

-

If the final digit is 5> drop all other #’s

Unit Conversions -

All #’s in calculations have associated units

Factor label method: calculations where 1 carries units for quantities -

Treat units as you would algebraic #’s

Atomic Masses -

An atom of an element has mass

-

Present mass scale is the Carbon-12 mass scale: 1 atomic mass units (amu) = 1/12 the mass of Carbon-12 atom

-

Atomic mass of an element is = to the average atomic mass of the naturally occurring element

Mass spectrometer: used to get accurate atom mass. Uses a mass : charge ratio of + atoms Fractional abundance: fraction of the total # of atoms that composes and isotope Periodic Table Period: horizontal row Group: vertical row Features: -

Where electrons in an element are located: where are the shells. s, p, d, f

-

How many electrons are in the shells: s: 2, p: 6, d:10, f:14

Metal: substance with luster, conducts electricity, solid and malleable. Found to the left of the staircase Nonmetal: no metallic characteristic. Found to the right of the staircase Metalloid: both metallic & nonmetallic characteristics. Staircase element

Molecular and Ionic Substances Molecular substance: substance composed

Polymer: large molecule made up of a chain

of like molecules

of small repeated molecules. Both natural

Molecular formula: exact # of different

and synthetic

atoms of an element in a molecule

Monomer: Small molecules that form

Structural formula: chemical formula that

polymers

shows how atoms bond together Ion: charged particle formed by gain or loss of election -

Metals tend to lose elections

-

Nonmetals tend to gain electrons

Anion: Gains electron, becomes -

Formula unit: group of atoms or ions explicitly symbolized in the formula

Cation: loses electron, becomes + Ionic compound: composed of anions and cations. Usually formed when s and p orbitals overlap.

Nomenclature: Ionic compound: name of cation then anion Monatomic ion: ion formed from a single atom Naming monatomic ions: -

Cations are named after element

-

If there's more than 1 cation for the element use roman numeral to indicate form

-

Anions are named with element stem name, then suffix “ide”

Polyatomic Ion: consists of 2+ atoms and carries electrical charge -

Most are oxyanions which are oxygen with another element

Naming oxyanions: -

Stem name from characteristic element with pre and suffix denoted by # of oxygens

# of Oxygens

Prefix

Sufix

1 extra

per

ate

Standard

ate

1 less

ite hypo

2 less

ite

*prefix thio m  eans 1 oxygen atom has been replaced by a characteristic element Binary compound: composed of 2 nonmetals or metalloids. Usually molecular and named with prefix system Binary naming -

More metallic element 1st

-

1st element name is exact, 2nd is the element stem name with the suffix ide

-

Add greek numeral prefix to denote subscript

Hydrate: compound that contains water molecules bonded to its crystals Hydrate naming -

Anhydrous compound + prefix to indicate # of waters\

Acids Acid: molecular compound that hydrogen ions when dissolved in water Oxoacid: acid containing H,O + another element

-

Names correspond with the oxoanion + acid at the end

Anion Suffix

Acid Suffix

ate

ic

ite

ous

*some binary compounds with H & non metals yield acids. These solutions are named with prefix hydro +  nonmetal stem name + ic  + acid The Wave Nature of Light Wave: continuously repeating change in matter or a physical field -

Light is an oscillation in electric and

-

magnetic fields -

Characterized by it frequency and

Visible light ranges from 400nm 800nm

-

wavelength

800nm = infrared

Wavelength (λ): distance between adjacent identical points Frequency (𝑉) : # of wavelengths that pass a point / second -

Wavelength and frequency are inversely proportional.

-

C=λx𝑉

Electromagnetic spectrum: range of λ or 𝑉 of electromagnetic radiation Quantum Effects & Photons Photoelectric effect: light has both wave and particle features E = nhv 

where E= energy of vibration

h = plank’s constant= 6.63 x 10^-34

N = principal quantum # v = fixed atom vibration Photon: particle of electromagnetic energy with E proportional to observed frequencies E = hv

Bohr's Theory of the H Atom Line spectrum: spectrum showing only certain wavelengths -

Electrons can only have specific energy values in an atom = energy levels

E = RH / n2

where n = principal quantum #, RH = 2.179 x 10^-18

When electrons transition between energy levels there is an energy loss.

-

If energy change in - energy is lost as a photon. (electron goes from higher energy level to lower 1)

-

If energy change is positive electron gains energy. (goes from lower to higher energy level) will only go up an energy level if there is a collision and absorption of light

Quantum Numbers -

1st 3 numbers define the electron position, the 4th accounts for the spin

Principal Quantum Number n: -

Electron energy depends on n: smaller n = closer to nucleus = smaller energy

-

Energy that relates to distance is potential

-

Orbital size depends on n, larger n value = bigger orbital

-

n= distance from the nucleus

-

n = 1, 2, 3…

Angular Momentum Number ℓ: -

Defines # of orbitals & shape

-

ℓ = n-1….

-

s = ℓ = 0. Can hold 2 electrons

-

d = ℓ = 2. Can hold 10 electrons

-

p = ℓ = 1. Can hold 6 electrons

-

f = ℓ = 3. Can hold 14 electrons

Magnetic Quantum Number mℓ: -

How many orbitals there are in the same shell with the same shape but different orientation

-

mℓ = -ℓ to +ℓ

Quantum Spin Number -

Described possible spin around its axis

-

Its + ½ or - ½

Electron distribution Hunds rule: all orbitals must be ½ full before any can be full Filling order: 1s2 2s2 2p6 3s2 3p6 3d10  4s2 4p6 … When forming a + ion, remove electron that's farthest away from the nucleus first Transition metals: make orbitals as even as possible. S orbital may not be full before adding to the d orbital. Electron promotion only happens if you’re 1 away from symmetry

Magnetism Paramagnetic: attracted by a magnetic field because of unpaired electrons Diamagnetic: not attracted by a magnetic field because there are no unpaired electrons

Periodic Trends Atomic radii: -

Distance of the outer electron from the nucleus

-

Increase to the left and down. The more electrons an ion has the larger it is

Ionization energy: -

Energy required to remove an electron from a gaseous atom

-

Increases up and to the right

-

Increase with each electron removed

-

+ valuse

Electron affinity: -

Energy released when a gaseous atom gains an electron

-

Increases up and to the right

-

- value = stable

Electronegativity: -

Measures the tendency of an atom to gain an electron, relative to other elements

-

Increased up and to the right

Oxides Basic oxide: reacts with acid: most metal oxides Acidic oxide: reacts with base: most nonmetal oxides Ionic Radii Ionic radii: measure of the spherical region around the nucleus where an electron is likely to be found -

Increases down any column

Isoelectric: different species with the same # & configuration of electrons

Chemical Bonding Polar vs. nonpolar bonds: -

Type of bond depends on the ΔEN between the 2 atoms

-

A>>>>B EN = ionic

-

A>B EN = polar covalent

-

A = B EN = covalent

Covalent bonds can share electrons in 2 ways -

Evenly: covalent

-

1 atom contributes both electrons: coordinate covalent

Octet rule: tendency of atoms to have 8 electrons in their valence shell Sigma (𝞂) and Pi (π) Bonds -

Multiple bonds are pi bonds

-

Multiple bonds are needed to satisfy

-

-

Total # of electrons in the structure

-

Valencies

When drawing orbital diagrams, first bond is a sigma bond. All others are pi. A pi bond has a portion above and below the axis

-

When Pi bonds are present p orbitals must be present

-

Pi bonds react faster than sigma because there is no orbital overlap

Resonance -

Structures without 1 uniqure lewis structure

-

Must have a pi bond

-

Only the placement of the pi bond can change, in reality there is no actual double bond, each bond is 1.5

Formal Charges -

# of electrons an atom has in a structure vs. what it started with

Formal charge = # of electrons in ground state - (lone pair electrons + ½ of each bond)

-

Sum of the formal charge = charge on the molecule

Lewis Structures -

Accounts for all outer shell electrons

-

Central atom is the least EN atom

-

Draw a single bond between atoms

-

Complete octet by adding electrons.

-

Excess electrons form multiple bonds

OUTER ATOMS MUST HAVE 8 Rules -

When there are multiple possible, choose the one with the lowest magnitude of formal charge

-

When 2 have the same formal charge magnitude choose the one with the - charge on the more EN atom

-

Choose formula without like charges on adjacent atoms

Failures to the Octet Rule Odd electron systems: species without an even # of electrons. Carcinogenic Incomplete: don’t have 8 electrons around the central atom Expanded: have more than 8 electrons around central atom -

Must have a d orbital to expand into

Molecular Shape / Polarity -

Lewis structure allows shape and polarity to be determined

-

Shape affects polarity: symmetry= non polar, no symmetry = polar

3 kinds of electron pairs -

Lone pair

-

Sigma bond

Molecular shapes Valence  Shell  Electron  R  epulsion (VSEPR)   model makes use of -

Electron pairs trying to be as far from each other as possible

-

Only free and sigma bonds effect shape

Framework Geometry -

Accounts for

-

all electron pairs

Actual molecular shape -

Molecule shape ignores lone pairs

-

Pi bond

Bond angles -

Free electrons require more space, ∴ lone pair bond angle > than expected, all other are smaller than expected

-

Multiple bonds require slightly more space than sigma

Summary Total e- pairs

bonded

lone

framework

geometry

Bond angle

2

2

0

linear

linear

180

3

3

0

Trigonal planar

Trigonal planar

120

3

2

1

Trigonal planar

bent...