CHEM 101: Midterm 1

What are the four points of atomic theory?

All matter consists of atoms, atoms of elements cannot be destroyed or chnaged by chemical reactions, atoms of a specific element are all the same, compounds tend to form molecules in a chemical reaction with specific ratios

What was the conculsion from the cathode ray experiment?

Electrical discharge consists of negatively charged particles and electrons are generated from all different types of matter (compounds, molecules, and elements)

What are "cathode ray particles" really?

Electrons

What is the mass-charge ratio of an electron?

The mass of an electron is approx. 1/1600 the mass of H

What was concluded from the Millikan oil-drop experiment?

The charge of an electron, which is -1.602 x 10^-19 C, and the mass of an electron, which is 9.109 x 10^-2

What was the concluson from the Rutherford/Gold Foil experiment?

Atoms are not only made up of electrons, but a more dense centre called a neutron as well which was discovered by backscattering of radioactive beam of particles that occured during the experiment

What are the characteristics of a proton?

Positively charged (1.602x10^-19 C), has the mass of one AMU

What are the characteristics of a neutron?

Has no charge, has the mass of one AMU

What is the characteristics of an electron?

Negatively charged (-1.602x^-19 C)

What does AMU represent?

Atomic mass unit (1.673x10^24 g)

What is an atomic number and what represents it?

The number of protons in an atom, represented by Z

What is a mass nuber and what does it represent?

The number of protons and neutrons in an an element, represented by A

What is atomic symbol?

Letter(s) given to each element to identify it

How does an element become an ion?

It gains or loses electrons

What is spectroscopy?

The study of light with matter

What wavelengths does visible light take up?

400-750 nm

What is absorption?

Excitation of an e- from a lower energy state to a higher energy state

What is emission?

Giving off energy (photons) from a high energy state to a lower energy state

What is an atomic spectra?

Lines of light that are visible at certain wavelengths when an atom is given energy

What is the conversion from nm to m?

___ nm = ___ 10^-7 m

What unit is eneergy measured in?

Joules (J)

What is the lowest possible energy state?

n = 1

What is happenign at energy level infinity?

The e- is no longer interacting with the p+/nucleus

What types of atoms can be represented by the Bohr Model for lien spectra?

Single electron systems (ex. H)

What is ionization?

The process of removing an e-, starting from the ground state (n = 1)

What are orbitals?

Allowed energies and regions of space that electrons occupy

What does wave-partical duality explain?

How matter and electrons are wave-like

In a circular electron orbit, what are the only types of numbers of wavelengths allowed?

Whole numbers (fractional numbers are forbidden as the wavelike movement would stop)

What is Heisenberg's Uncertainty Principal?

It is not possible to know the position and momentum of a moving partcile at the same time

How can a wavefunction for an electron be obtained?

By using the Shrodinger Equation

What is probability density?

A measure of the probability of fidnign an electron in an atom

What is an electron density diagram for an H atom?

A picture of a density of dots that represents the probability of finding an electron

What is a probability contour?

An orbital

What are quantum numbers?

Parts of the solution to the Schrodinger Equation that describes an orbital and the electrons within one

How is a principal quantum number represented and what does it determine?

It is represented by n and determines the size and energy of an orbital

What are the allowed values for a principal quantum number?

Integers

What is the symbol for angular momentum quantum number and what does it determine?

It is represented by lowercase L and determines an orbitals shape

How is magnetic quantum number represented and what does it determine?

It is represented by m subscript lowercase L and determines the orietation of an orbital

What are the allowed values for angular momentum?

0 to (n-1)

What are the allowed values for magnetic quantum numbers?

-lowercase L to +lowercase L

What is a shell?

Any orbitals witht he same principal quantum number (n)

What is a subshell?

A shell with subscript s/p/d/f

What shape are s orbitals?

Spherical (circular on paper)

What is a radial node?

A spherical region around an atom's nucleus where the probability of finding an electron is zero

What is an angular node?

A nodal plane that passes through the nucelus of an atom

What does a subshell letter (s/p/d/f) with a subscript x/y/z mean?

The orbital forms with the x/y/z-axis in between the lobes

What does a subshell letter (s/p/d/f) with a subscript x^2/y^2/z^2 mean?

The orbital forms with the x/y/z-axis dircetly through the lobes

What does the d subscript z^2 orbital look like?

A "dumbell" orbital formed through the z-axis with a "donut" or ring around it flat with the x and y-axes, it has 2 conal nodes

How many lobes does a p orbital have?

2 (aka "dumbell")

How many lobes does a d orbital have?

4 (aka "4 leaf clover")

How do you determine the numbr of nodes an orbital has?

n - 1

What is a nodal plane?

A type of angula node that is planar

What is a conal node?

A type of angular node that is cone shaped

What level of energy does an orbital need to be more stable?

Lower energy

What does it mean for 1-electron orbitals to be degenerate?

They share the same energy (and are in the same shell)

What does it mean for multi-electron orbitals to be degenerate?

They share the same energy (and are in the same subshell)

What is the relationship between nuclear charge (# of protons in nucleus) and orbital energy?

Greater nuclear charge lowers orbital energy

What raises orbital energy?

Electron-electron repulsions

What are sheidlign electrons and how do they work?

They are inner electrons that shield outer electrons from full nuclear charge and therefore have higher energy

How do you calculate Zeff?

Z - # of shielding e-

What is spin (quantum number)?

m subscript s; it determines spin up or spin down of an orbital

What is the Aufbau principal?

Electrons should fully occupy the lowest energy orbitals available before any higher energy orbitals are occupied

What order do energy levels of subshells appear in from lowest to greatest?

1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p

What is the Pauli exclusion principal?

Orbitals can hold a maximum of two electrons and they must have opposite spins; in a given atom, no two electrons can hold the same quantum numbers

What is Hund's rule?

When orbitals of equal energy are available, the number of unpaired spins must be maximized

What is the s block of the periodic table?

Columns 1 and 2

What is the f block of the periodic table?

Periods 6 and 7 (just the extra elements at the bottom the the periodic table)

What is the d block of the periodic table?

Columns 3-12

What is the p block of the periodic table?

Columns 13-18

What is the exception for electron configuration Cr [Ar] 4s^1 3d^5?

Cr [Ar] 4s^2 3d^4

What is the exception for electron configuration Cu [Ar] 4s^1 3d^10?

Cu [Ar] 4s^2 3d^9

What are velence shell lectrons and how are they identified?

They are outer electrons and are in the shell of the highest principal quantum number

What are core electrons?

Electrons below the valence shell

What relationship do metals have with electrons?

They tend to lose valence e- and form cations

What relationship do non-metals have with electrons?

They tend to gain valence e- and form anions

When writing the electron configurations of elements with a positive charge, what electrons do you remove first?

The electrons in the highest shells first

What does it mean for substances to be paramagnetic?

It has unpaired e- and it is attracted to an external magnetic field

What does it mean for substances to be diamagnetic?

All of it's e- are paired and it is weakly repelled by a magnetic field

How do you determine if the ions in a substance are para/diamagnetic

Write out electron configurations for each ion seperately, draw configurations using the arrow format, evaluate

How do you tell if a substance is automatically diamagnetic?

It has noble gas electron configuration

How is size of an atom defined?

It is half the distance between nuclei in homoatomic metallic or covalent bonds

What is the trend of atomic radii?

Across a period (row), atomic size decreases; down a group (column), atomic size increases - atomic size decreases from bottom left corner to top right corner of periodic table

What is the relationship between effective nuclear charge (Zeff) and size of atomic radii?

The greater the effective charge, the smaller the atom is due to the e- being more tightly held together

What is the relationship between principal numbers and size of atomic radii?

The greater the principal number, the larger the the atom

What happens when you add an electron to an atom?

It increases electron-electron repulsion --> anions are larger than thier corresponding neutral atoms

What happens when you remove an electron to an atom?

It decreases electron-electron repulsion --> cations are smaller than thier corresponding atoms

What is an isoelectronic series?

Elements/ions with the same electron configurations

How to determine the size of isoelectronic species?

Thier charge (cations are smaller, anions are larger)

What is ionization energy?

The energy required to remove an electron from a gaseous atom or ion; cation formation

What is the trend of ionization energy?

Across a period, ionization energy increases; down a group, ionization energy decreases (Bottom left corner of periodic table is lowest IE and top right corner is highest IE)

What are the exceptions to the ionization energy trend?

The decrease of energy between group 2 and 13 (Be/B) and between group 15 and 16 (N/O) due to the introduction of the "p" orbital (write e- config. to understand)

What are successive ionization energies?

Ionization energies that increase as each e- is removed

How do you tell what charge (and how many e- to add/remove) to find the largest jump in successive ionization energy for an atom/ion?

Look at most common charge on periodic table

What does a large jump in ionization energy mean?

A core e- was removed from an ion

What is electron affinity?

The energy change associated with the addition of an e- to a neutral atom in the gas phase (IE)

What does a negative electron affinity mean?

Energy is released and adding e- is favourable

What does a positive electron affinity mean?

Energy is added and we are forcing the atom to accept e- when e-/e- repulsion is high which is unfavourable

What is the trend of electron affiniity?

EA tends to become more negative across a period (ions like to form anions); EA tends to become less negative down a group (ions prefer to stay as a neutral atom or becomes a cation)

What group has the highest electron affinity?

Group 17 or 7A

Do noble gases have electron affinity? Why or why not?

They do not; it is not favourable for them to gain e- because all thier shells are already full