Chem 181 Test 2

Front 1

Law Of Conservation Of Mass

Back 1

Total mass of reacting substances is equal to the total mass of the products formed

Front 2

Empirical Formula of Compound

Back 2

the formula of a compound expressed as the smallest possible whole-number ratio of subscripts of the elements in the formula

For example, CH3COOH has two carbons, four hydrogens and two oxygens. So we could write the formula like this: C2H4O2 and so it reduces to CH2O

Front 3

Deduce Empirical Formula

Back 3

Here's an example of how it works. A compound consists of 72.2% magnesium and 27.8% nitrogen by mass. What is the empirical formula?

(1) Percent to mass:

Assume 100 g of the substance, then 72.2 g magnesium and 27.8 g nitrogen.

(2) Mass to moles:

for Mg: 72.2 g Mg x (1 mol Mg/24.3 g Mg) = 2.97 mol Mg
for N: 27.8 g N x (1 mol N/14.0 g N) = 1.99 mol N

(3) Divide by small:

for Mg: 2.97 mol / l.99 mol = 1.49
for N: 1.99 mol / l.99 mol = 1.00

(4) Multiply 'til whole:

for Mg: 2 x 1.49 = 2.98 (i.e., 3)
for N: 2 x 1.00 = 2.00

Front 4

First Periodic Table

Back 4

Physical and chemical properties of the elements

Front 5

Implication of layer or shell structure of atoms

Back 5

Noble-gas-like core with valence electrons outside of the core

Front 6

Valence electrons

Back 6

Electrons in the outermost occupied shell of an atom. Participate in the formation chemical bonds

Front 7

Light

Back 7

• a form of energy
• travels through space at c = 3.00 X 108 m/s
• consists of oscillating electric and magnetic
fields coupled together
• called electromagnetic radiation

Front 8

Wavelength

Back 8

length of one complete cycle (wave)(λ)
~meters

Front 9

Frequency

Back 9

number of waves passing a fixed point per
second.(ν)
~1/s

Front 10

Amplitude

Back 10

height of crest (or depth of trough) of the
waves

Front 11

wavelength and frequency are related by

Back 11

ν=c/λ
frequency = speed of light/wavelength

Front 12

Photon energy

Back 12

Eph=hv
Energy of photon = plank's constant x frequency
-photoelectrons was found to be proportional to the frequency of the light

Eph=(hc)/λ

Front 13

Relation of wavelength, frequency, photon energy

Back 13

Increases:
Wavelength (λ) -->
Frequency (v) <--
Photon Energy (Eph=hv) <--

Front 14

Atomic emission spectrum

Back 14

The pattern of wavelengths emitted is unique for every element
-the simplest pattern is emitted from hydrogen
-Pattern of wavelengths emitted by an element is exactly the same as the pattern of wavelengths absorbed from the white light
-Energy of electron is quantized

Front 15

Atomic absorption spectrum

Back 15

Only radiation of certain frequencies is absorbed by the sample.
-Emission spectrum appears as a series of colored lines against a dark background
-Absorption spectrum is a series of dark bands at the frequencies where light is absorbed against a colored background.

Front 16

Relation of spectrums

Back 16

Only frequencies of light where the energy corresponds to the energy difference between any 2 states(energy levels) in the atom are readily absorbed or emitted.

Front 17

Niels Bohr

Back 17

The electron in a hydrogen atom is restricted to only certain circular orbits about the nucleus

Front 18

DeBroglie

Back 18

Matter which appears to be particle-like, might also display wavelike properties under certain conditions.

λ=h/(mv)

Front 19

Quantum Theory

Back 19

Atom can exist in only certain allowed energy levels.

Front 20

Quantum Number n

Back 20

n = 1,2,3… is called the principal quantum number (determines
energy level or shell of the electron for a given orbital)

Front 21

Quantum number l

Back 21

l = 0,...(n-1) is called the angular momentum quantum number
and it designates the subshell (l = 0, 1, 2, 3 corresponds to
the s, p, d, and f subshells) (it also determines the shape
of the orbital)

Front 22

Quantum number ml

Back 22

ml = - l,…0,…l is called the magnetic quantum number and it
designates the specific orbital (determines the 3D
orientation of the orbital)

Front 23

Relation of quantum numbers

Back 23

for n = 1, the only value of l allowed is 0, so the only subshell
within the 1st shell is the 1s subshell. And for l = 0 the only
value of ml allowed is 0. So there is only one orbital in the
first energy level,

Front 24

Quantum numbers

Back 24

n = 1,2,3…
l = 0,...(n-1)
ml = - l,…0,…l

Front 25

Quantum numbers things to know

Back 25

• there are n subshells in
each energy level (shell)
• there are 2l+1 orbitals in
each subshell
• there are n2 orbitals for
each value of n
• all orbitals in the same
shell (same n) have the
same energy (hydrogen
only)
• the electron can live in
only one orbital at any
point in time

Front 26

Pauli Excursion

Back 26

The Pauli Exclusion principle requires that an orbital can contain a maximum of two electrons and the two electrons must have opposite (paired) spins.

Front 27

Hund's Rule

Back 27

When multiple orbitals of the same energy are available, electrons prefer to occupy separate orbitals and have the same spin state.

Front 28

Order of Electron Configuration

Back 28

1s 2s 2p 3s 3p 4s 3d 4p 5s 4d 5p 6s 4f 5d 6p 7s 5f 6d 7p

-Each row begins when a new energy level is started.

Front 29

Molecular(Covalent) compound

Back 29

generally formed from the reaction of non-metal elements with other non-metal elements, e.g. hydrogen + oxygen
-consist of neutral molecules

Front 30

Ionic compound

Back 30

generally formed from the reaction of metal elements with non-metal elements, e.g. sodium + chlorine
-consist of positive and negative ions (atoms or molecules that carry an electrical charge)

Front 31

Ionization energy

Back 31

The energy required to remove an electron from the highest energy occupied subshell of an individual atom or ion in its ground state.

-The stronger the attraction between the nucleus and the outermost electron, the higher the ionization energy will be.

Front 32

Ionization Energy trend

Back 32

increase across row of periodic table, down group, and jumping from end of one row to start of the next

Front 33

Effective Nuclear Charge

Back 33

Zeff, increases across each row (increased shielding due to new electrons is not sufficient to compensate for additional protons in nucleus)

-When a new row begins, the outermost electron is in a new shell, which is very effectively shielded from the nucleus by the electrons in the s and p subshells of the previous shell.

Front 34

Electron Affinities

Back 34

The energy released or absorbed when an additional electron is added to an individual atom

e.g. Na(g) + e-  Na-(g) Eea = electron affinity

Front 35

Atomic Radii

Back 35

Atomic size also depends on how strongly the valence electrons are attracted to the nucleus of the atom.

Front 36

Forming Ionic Compunds

Back 36

The formulas for ionic compounds are empirical formulas (the subscripts provide the simplest ratio of ions that balances the charge) e.g. MgCl2, Na2S, Al2S3 (the formula represents the neutral compound)

Front 37

Electron Configs. for Transition Metals

Back 37

for transition metal cations:
•remove electrons from occupied subshell with highest value of n
•e.g. Fe: [Ar]4s23d6 and Fe3+: [Ar]3d5

Front 38

Naming Ionic Compounds

Back 38

-The -ide ending is added to the name of a monoatomic ion of an element.

-Some polyatomic anions contain oxygen. These anions are called oxyanions. When an element forms two oxyanions, the one with less oxygen is given a name ending in -ite and the one with more oxgyen is given a name that ends in -ate.

Front 39

Naming Molecular Compounds

Back 39

the name of a molecular compound indicates how many atoms of each type of element are present in the compound. This is accomplished using prefixes. If there is only one atom of the first element, no prefix is used. It is customary to prefix the name of one atom of the second element with mono-. For example, CO is named carbon monoxide rather than carbon oxide.

SO2 - sulfur dioxide
SF6 - sulfur hexafluoride
CCl4 - carbon tetrachloride
NI3 - nitrogen triiodide

Front 40

Formula Unit

Back 40

is a representation of the compound's formula. For example, the formula unit of NaCl is one Na^+1 ion and one Cl^-1 ion. The formula unit of AlCl3 is one Al^+3 ion and three Cl^-1 ions. Ionic compounds don't have separate bundles of atoms like molecular compounds do, so the formula unit is just the smallest number of ions that it takes to represent the formula.