Chem 142 UW Exam 1

The atom

Consists of a small nucleus with a positive charge containing most of the weight. Has an electron cloud with mostly empty space but some electrons as well

Protons

The chemical identity of the element

Electrons

Ionic character of atom

Neutrons

Isotopic character of the atom

Atomic number (Above element on PT) represents...

Number of protons

Mass number represents...

Sum of protons and neutrons

Atomic mass (Under element on PT) represents...

An average of the atomic masses of common isotopes

Isotope

An elements with the same number of protons but different neurons and therefore different atomic masses (12^C, 13^C, 14^C)

Anions _____ electrons, giving them a ____ charge

Gain, Negative

Cations _____ electrons, giving them a _____ charge

Lose, Positive

T or F? Chemical reactions do not change elements

True, except with nuclear reactions

T or F? Atoms of each element have the same number of protons

True. Isotopes of an element have a different amount of neutrons

Properties of a Metal (4 total)

1) Conduct heat/electricity 2) Malleable 3) Ductile 4) Tend to lose electrons (+ charge)

Properties of Nonmetals (3 total)

1) Dull/brittle 2)Nonconductor 3) Gain electrons (-charge)

Properties of Semimetals

Have properties of both nonmetals and metals

Groups move....

across the periodic table

Periods move...

up and down the periodic table

Group 1A

Alkaline metals

Group 2A

Alkaline Earth Metals

Group 7A

Halogens (nonmetal)

Group 8A

Noble Gases (nonmetal)

Transition metals have multiple types of _____

cations

Main types of bonds that can be formed

Ionic (transfer of e-) and covalent (sharing e-)

Molecule formation occurs in an attempt to...

complete an octet for both atoms

Chemical bonds

Hold atoms or ions together in a compound

Ionic compounds

The result of an electron transfer. Consists of a network of anions & cations with an overall charge of 0

Colors of the visible spectrum and range they're in?

ROYGIBIV: Red (700nm), orange, yellow, green, blue, indigo, violet(400nm).

Order of electromagnetic spectrum (low to high wavelength)

y rays, x rays, ultra violet, visible spectrum, infrared, microwaves, radio waves, long radio waves.

Order of electromagnetic spectrum (low to high energy/frequency)

Long radio waves, radio waves, microwaves, infrared, visible spectrum, ultra violet, x rays, y rays.

Y rays

Around 10^24-20 HZ (Frequency)

Around 10^-16 to -12 M (Wavelength)

Ultra violet

Around 10^16 HZ (Frequency)

Around 10^-8 M (Wavelength)

X rays

Around 10^18 HZ (Frequency)

Around 10^-10 M (Wavelength)

Visible

Around 10^15 HZ (Frequency)

Around 400nm-700nm (Wavelength)

Infrared

Around 10^14-12 HZ (Frequency)

Around 10^-6 to-4 M (Wavelength)

Microwaves

Around 10^10 HZ (Frequency)

Around 10^-2 to 0 M (Wavelength)

Radio waves

Around 10^8-6 HZ (Frequency)

Around 10^0-2 M (Wavelength)

Long radio waves

Around 10^4-0 HZ (Frequency)

Around 10^4-8 M (Wavelength)

Wavelength ("lamda" or the upside down Y thing)

Distance between 2 consecutive peaks.

Frequency ("Nu" or the fancy v)

Number of waves (or cycles) that pass a given point in space per second

Energy (E)

Increases with frequency, decreases with wavelength

Atomic emission

The emission of electromagnetic radiation that occurs when an atom relaxes after being excited via heat/electricity.

This emitted light appears in discrete bands of color at specific wavelengths

Emission spectrum corresponds to...

a particular set of Fraunhofer lines

Atoms can only emit or absorb electromagnetic energy at....

specific discrete wavelengths

The energy that an atom can absorb or emit is

quantized

Blackbody radiation

Continuous electromagnetic radiation emitted from heated objects, where the intensity/peak depend on the temperature of the emitting body

In blackbody radiation, as temp ______, intensity of emission _____, and wavelength shifts to _____ wavelengths

increases, increases, smaller

Identify what each letter represents in the equation:

change in E=nhv

1) change in E= change in energy

2) n= an integer (1,2,3)

3) h=Planks constant 6.626x10^-34 JxS

4) v= frequency

hv

a photon of energy

How do you solve a problem asking for the energy of a photon?

1) If frequency is not given, use equation frequency= c/wavelength where c=3.00x10^8 m/s

2) Solve Ephoton=hv equation where h=Planks constant of 6.626x10^-34 JxS

Diffraction of light

The bending of light as it passes an object. Shows that light interacts with matter

Wave particle duality

The idea that electromagnetic radiation can appear to behave as either a wave or particle depending on the situation.

Diffraction patterns are a consequence of the wave like nature of light

Backbody radiation & atomic emission spectra are consequences of the particle like nature of light

Diatomic elements

Have No Fear Of Ice CoLd BeeR

H, N, F, O, I, Cl, Br.

Orbit energies are quantized and described according to which equation? (Bohr)

E=-2.178x10^-18 J (Z^2/n^2)

where Z= The atomic number & n= an integer

By convention, E=0 at n= infinity because...

there is no interaction between nucleus and electron

What happens after energy level n=7?

Since energy levels get closer as n increases, any energy level beyond n=7 is considered essentially continuous because of how closely spaced they are

Lyman series

UV emission; Electrons drop from higher energy orbitals into n=1

Balmer series

Visible emission; Electrons drop from higher energy orbitals into n=2

Paschen series

Infrared emission; Electrons drop from higher energy orbitals into n=3

The Bohr model

(can be used to predict change in energy for any 2 energy levels)

change in E=Efinal-Einitial OR

-2.178x10^-18 J (1/nf^2-1/ni^2)

If answer is negative it's emission, if the answer is positive it's absorption

Quantized vs Continous Spectra

Quantized: The idea that energy levels are distcretized, so only certain direct emissions are allowed --> Atomic emission

Continuous: Energy levels are so close together that essentially any direct emission is possible. --> Blackbody radiation

T or F Electromagnetic energy is quantized in discrete amounts we call photons

True

When electrons move from one energy level to another...

light is emitted or absorbed in discrete amounts and are seen as lines in a spectra

Bohrs model wasn't good enough because it failed to...

accurately describe the spectra of multi-electron atoms and assumed a deterministic path for e-

did not take into account the wavelike nature of the electron

Describe emission

When electrons relax in energy levels. Happens when an electron is given energy (ex:heat) and goes into a higher energy state. But it doesn't want to be there, it wants to be stable. So it goes down a orbit, gains the difference in energy, giving off light

Describe absorption

Absorption of light causes electrons to go higher. HAVE to have a specific amount of energy or an excess for the electron to go up.

Wave mechanics/quantum mechanics

An electron can adopt only certain "standing wave" patterns of motion when subjected to a constraining potential

Wave mechanics--> Wavefunctions

Where we are most likely to find the electron relative to the nucleus, with space 'dead space' separating each area called nodes

Think of guitar strings! Vibrations must go to 0 at each end because the string is constrained at each end. These constrained ends are nodes!

Essentially, it's a probability amplitude.

Probability density

The square of wavefunction. Describes where you will find the largest amount of motion (kinetic energy) in the standing wave

When a wavelike object becomes constrained, it's energies become...

quantized

Equation for finding total energy

Etotal=KE+PE

Principle quantum number (n)

Determines electron energy level; can be integers from 1 to infinity. Related to size and energy of the orbital

The higher n, the greater the distance between the nucleus and electron, and the higher the energy (think, if they're further away, it requires more energy to keep them together)

The probability of a wave function is refereed to as...

an orbital

Orbitals are characterized by a set of quantum numbers: ___, ___, and ___.

n, l, m

Angular momentum quantum number (l)

range of 0 or positive integers that determine the shape of an orbital

l=0=s

l=1=p

l=2=d

l=3=f

Magnetic quantum number (ml)

range of integer values (-&+) that determine orientation in space of the angular momentum (l) associated with the orbital

energy ______ as n _______

increases, increases

If n= 1 what can l, ml, and the subshell(s) be?

l=0

s=s

ml=0

If n= 2 what can l, ml, and the subshell(s) be?

l=0 or 1

s=s or p

ml=-1, 0, 1

If n= 3 what can l, ml, and the subshell(s) be?

l= 0, 1, or 2

s= s, p, or d

ml=-2, -1, 0, 1, or 2

If n= 4 what can l, ml, and the subshell(s) be?

l=0, 1, 2, or 3

s= s, p, d, or f

ml= -3, -2, -1, 0, 1, 2, 3

Describe the s orbital shape

spherical

Describe the P orbital shape

Lobed with a node at the origin.

Think of a dumbbell, with a positive and a negative side.

What is a node? How do you know how many there are?

An area of 0 electron density.

Number of nodes= n-1

What type of nodes are there?

Angular (goes straight through electron) and radial (creates a circle)

Describe D orbital shape

Think flower power almost-- 4 round parts connected at center

Describe F orbital shapes

A pure mess. If it's really complex it's definitely this one

Orbitals of the same n but different l are considered...

to be of equal energy, or degenerate

The ground energy level is

the lowest energy orbital (1s)

Pauli exclusion principle

No 2 electrons may occupy the same quantum state simultaneously; Meaning that only 2 electrons may occupy a given orbital, and they must have opposite spin.

We fill orbitals in order of increasing energy, not n. Therefore, we fill in this order:

If the electrons are ever filled in a different order, they are in...

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, 5f, 6d, 7p, 8s.

...an excited state

Hund's rule

The orbitals in a degenerate series (such as 2p) must each have an electron before any of them can have two and the electrons in one must have opposite spin

Valence shell

The s and p orbitals in the highest occupied n level. To have a full valence shell is to be stable!

Core electrons

Electrons in an orbital with an n lower than the highest n (ex: 1s)

Aufbau principle

Orbitals are filled in order of increasing energy, not increasing n. Therefore, 3d is filled after 4s, not 3p

Exceptions to filling orbitals

Chromium and the elements below it. Instead of [Ar] 4s^23d^4, it's [Ar] 4s^1 3d^5

Copper and the elements below it too. Instead of [Ar] 4s^2 3d^9, it's [Ar] 4s^2 3d^10

Atoms in the same group have the same valence shells, so they tend to...

have similar chemical properties

In general, elemental properties correlate...

down a group of elements

Ionization energy is

the energy required to remove an electron from a gaseous atom or ion, and requires an input of energy. The greater the ability of an atom to "hold on" to it's electrons, the higher the ionization energy

It takes significantly more energy to remove a _______ electron than a ______ electron

core, valence

How does ionization increase across the periodic table? Why?

from left to right and up across the periodic table. This is because...

1) As number of protons in a nucleus increases, attraction between the nucleus and valance electrons increase

2) Less distance between electrons and nucleus increases attraction.