Quantum mechanics Flashcards
What is provided by “ψ2”?
Information about tan electron’s location in an allowed energy state; it gives us the probability that an electron is at that given position.
What is an orbital?
A specific distribution of electron density around an atom.
How many quantum numbers we use to describe orbitals?
Principal quantum number = n (size)
Azimuthal quantum number = l (shape)
Magnetic quantum number = ml (orientation)
mS = Orientation of electron in an orbital
As n increases the orbital becomes_____________, and the electron is __________ from the __________. Also, the energy associated with an orbital __________ as ___ increases.
Bigger, further away, nucleus, increases, n.
If orbitals have the same value of n, they are considered to be in the same…
Electronic shell
If orbitals have the same value of n and l, they are considered to be in the same…
Electronic subshell
An individual orbital is defined by a unique set which numbers?
n, l, and m1
How is the azimuthal number defined?
Values from 0 to n-1 and letters (s, p, d, f)
How is the m1 number defined?
-l to +l
How is the ms number defined?
2l + 1
What are the numbers related to the letters of the azimuthal number?
s(0), p(1), d(2), f(3)
When describing orbitals we are talking about the probability that an electron…
Will be in a given position.
The p orbital has 3 subshells
True
How many subshells does a d orbital have?
Five
How many subshells does a f orbital have?
Seven
What is the possible number for ms?
-1/2 or +1/2, referred to as spin up or spin down
Two electrons can have the same four quantum numbers.
False. Each electron has a specific set of quantum numbers. This is called the Pauli Exclusion Principle
Electrons will start filling up the ______ energy orbitals. This is referred to as the _________.
Lowest; ground state
What are called two electrons or opposite spin?
Paired
What is called an electro by itself?
Unpaired
What is the Hund’s rule?
“For degenerate orbitals, the lowest energy state (most stable) is obtained when the number of electrons with the same spin in maximized.”
What is the primary force behind Hund’s rule?
Electrostatic repulsion between electrons
What are the most stable elements?
The ones with full shells. There is no room for electrons to move, thus elements with full shells are particularly stable and nonreactive.
What are the electrons that drive reactivity and atom behavior?
Valence electrons
What are the other electrons called?
Core electrons
Elements where d orbitals are being filled are called…
Transition Metals
What is the similarity between Na, K, and Rb?
All have noble gas core and one s electron; also have similar chemical properties
The elements in which the ____ orbitals are being filled are called ____________; the elements in which the ____ orbitals are being filled are called ______________.
4f; lanthanides; 5f; actinides
What is the electron configuration of Chromium?
[Ar]4s13D5; this is an exception and it happens because subshells that are either completely full or exactly half full, are especially stable.
In a periodic table we can see that __________ come after a __________.
Soft reactive metal comes after a nonreactive gas
What do we use to describe the average environment created by the nucleus and other electrons in the atom?
Effective nuclear charge, Zeff; Zeff = Z-S, with S being a constant related to the core electrons
As we move across the periodic table from left to right, Zeff ________. As we go down a column, Zeff stays _________ .
Increases, constant.
What is the atomic size?
The average radius of the electron distribution in an atom.
We have similar radius numbers in bonding and nonbonding molecules.
False.
According to chemical trends, the atomic radius:
Increases if we go down a column, and decreases if we move across the periodic table.
What does ionic radii depend on?
Nuclear charge, the number of electrons, and the orbitals of the valence electrons.
For cations the ionic radius is…
Smaller than the atomic radius.
For ions of the same charge the size…
Increases as we go down the periodic table.
The higher the ionization energy, the easier it is to remove an electron.
False, the harder it is.
Ionization energy increases as we move from left to right and up a group.
True.
What are the most important periodic trends?
Electronegativity, ionization energy, electron affinity, atomic radius and metallic character.
What is one exception in the electron configuration of ions?
Fe. Its regular configuration is [Ar]4s23d6. Upon the first ionization it loses one electron in the s orbital; upon the second one it loses the last electron on the s orbital. Only in the third ionization it actually loses electrons in the d orbital.
Why are atoms in group 6A different than the rest of the periodic table?
Because they have a full n shell and an exactly half full p shell, which is specially stable.
Electron affinity ____________ as we go across the periodic table from left to right.
Becomes more negative
If EA is greater than zero, then…
An electron will not attach itself to an atom.
We describe an element as metal, nonmetal, or metalloid depending on the…
Configuration of the element.
What are chemical bonds?
The force that holds the atoms in position in a substance
What are the three types of chemical bonds?
Ionic bonds - Electrostatic interaction between ions; generally found between a metal and a nonmetal.
Covalent bonds - Sharing of electrons; generally found between nonmetals.
Metallic bonds - Electrons are shared through the lattice; generally found between metals.
The number of valence electrons as well as the electron configuration determine…
how two atoms are bonded together.
What are the conditions for the formation of ionic bonds?
Ionization of the metal (should be low), and electron affinity of the nonmetal (should be high)
Lattice Energy
It is the energy required to separate a mole of an ionic solid into its gaseous ions.
Formation of ionic solids from their constituent elements is a highly endothermic process.
False, it is highly exothermic
As ions get larger, the spacing between ions in a lattice decreases and as a result:
The lattice energy decreases.
Changes in lattice energy based on charge are much greater than changes based on…
size
Bonds where electron are shared equally are called…
Nonpolar covalent bond
If one atom exerts a greater pull on the electrons than the other, we refer to it as a…
polar covalent bond
What values do we use to predict bond polarity?
EA<0.5 - nonpolar covalent
EA>2.0 - Ionic
0.5
Electronegativity ______ as we go from left to right, and it ________ if we go down a group.
Increases, decreases
What is Electronegativity?
The ability of an atom to attract electrons to itself in a molecule. It is similar to electron affinity but it refers to atoms in a molecule, instead of single atoms.
What is the most electronegative atom? And the least electronegative?
Fluorine (F; 4.0); Cesium (Cs; 0.7)
Effective nuclear charge
Increases when we go across a period. Number of protons increase but number of shielding e is constant, More or less constant down a group
Atomic size
More protons pulling electrons in tighter; from left to right there is a decrease, from top to bottom it increases (shells get larger)
Ionization energy
Left to right ionization energy increases (elements get closer to noble gases, it takes more energy to remove electrons) It decreases from top to bottom.
What are the three exceptions for the Octet rule?
Molecules or ions with an odd number of electrons; molecules or ions in which an atom has fewer than 8 valence electrons; molecules or ions in which an atom has more than 8 valence electrons.
What are radicals?
Molecules or atoms with an odd number of valence electrons. They are highly reactive. One example is NO.
What is the strength of the covalent bond (or bond enthalpies)?
The amount of energy required to break that bond.
The more we increase the number of bonds,
bond strength increases
The more we increase the number of bonds,
the shorter they get
What does VESPR stand for and how does it define electron groups?
Valence Electron Shell Pair Repulsion; lone pairs, single bonds, double bonds, and triple bonds.
What are the five geometric arrangements we can have for electron groups?
Linear (2 groups)
Trigonal planar (3 groups)
Tetrahedral (4 groups)
Trygonal bipyremidal (5 groups)
Octahedral (6 groups)
Electron geometry is…
The placement of electrons in a molecule
Molecular geometry is…
The placement of atoms in a molecule
In any molecule with four electron groups, the electrons will rearrange themselves in a _________
Tetrahedron
An atom with linear geometry has ___ atoms groups and will present an angle of:
Two
An atom with trigonal planar geometry has ___ atoms groups and will present an angle of:
Three
What kind of structure is this and how many bonds does it have?
Tetrahedral geometry; it is seen in molecules with 4 bonds. with four sp3 orbitals)
What are the positions we can have in an atom?
Axial positions and equatorial positions.
Trigonal Bipyramidal Geometry has how many bonds? And which angles?
5 bonds; 90 and 120 angles
Which geometrical structure is this, how many bonds does it have, and what is its angle?
Octahedral geometry, 6 bonds, angle 90°
In molecular geometry we desconsider lone pairs when drawing structures.
True. A tetrahedral structure for electron geometry is not necessarily going to be the same for molecular geometry, like in ammonia (NH3), for example
If all electron groups are bonds then the electron geometry and molecular geometry will be similar
True
In moleculr geometry, if you have 3 electron groups but one of them is a lone pais, then the structure will be
Linear, bent
As the number of electron domain increases, the number of possible molecular shapes increases
True
What do methane, ammonia, and water have in common?
They all have four electron domains, and a tetrahedral electron structure.
Non-bonding pairs are slightly more ___________ than bonding pairs and have a slighty __________ density than bonding pairs.
Repulsive, higher charge; this causes them to push the electrons a little bit more, distorting the angles.
Placing lone pairs in equatorial positions does what towards electron pair repulsion?
Minimizes it
Dipole moments are __________ therefore they have ___________ and _____________.
Vectors, magnitude, momentum
If the vectors cancel each other out, then the dipole moment is 1
False. It is zero, they cancel each other, therefore there is no displacement.
In general, if the central atom of a molecule is symetrically surrounded by atoms of the same element, the it is:
Non-polar
Orbitals do not have to be the same type to do what?
Overlap and form a bond
What is the optimal distance?
It is the distance where we will have bonds connecting.
What are Sigma bonds?
Bonds where the electron density is located on the axis
What are pi bonds?
Bonds where the electron density is located off the axis
The lobes of the p-orbitals overlpa to form the pi bond, located off axis. On-axis electrons are from the overlap of sp2 electrons in a theta bond.
