Ch 1: Covalent Bonding and Shapes of Molecules Flashcards
What do shells define?
The probability of finding an electron in a certain region
What is a shell?
A region of space surrounding the nucleus that can be occupied by electrons
What are 3 effects of shells?
Electrostatic attraction between the electrons and the nucleus, electrostatic repulsion between electrons, and the wavelike nature of an electron
What does it mean if something is quantized?
It has specific values rather than a continuum of values
What is delocalization?
The spreading of electron density over a larger volume of space
How many electrons can a shell hold?
2n² electrons, where n is the number of the shell
Electrons in the first shell are the _____ in energy.
lowest
Electrons in the higher-numbered shells are held _____.
less strongly than the electrons in the lower-numbered shells
Shells are divided into subshells given by _____ and within these subshells, electrons are grouped into _____.
s, p, d, f; orbitals
What is an orbital?
A region of space that can hold 2 electrons
What is the ground-state electron configuration of an atom or molecule?
the lowest electron configuration
What 3 rules determine ground-state electron configuration?
Aufbau Principle, Pauli Exclusion Principle, Hund’s Rule
What is the Aufbau Principle?
Orbitals are filled in order of increasing energy
What is the Pauli Exclusion Principle?
No more than 2 electrons can occupy an orbital, and they must have opposite (paired) spins
What is Hund’s Rule?
When degenerate orbitals are available, but there are not enough electrons to fill all of them completely, one electron is put in each before a second one is added to any.
The spins of the electrons in the degenerate orbitals should be parallel to reduce static repulsion- the convention is to have the spins going up.
What is energy?
the ability to do work
What is potential energy?
stored energy that is released when the object is released
What is an excited state?
a state of a system at a higher energy than the ground state
All of nature seeks _____.
its lowest energy state
When the electrons of an excited state are rearranged back to the ground state, _____.
the potential energy held by that unstable system is released and work is done
What is ionization potential?
the energy needed to remove an electron from an atom or molecule
Electrons closest to the nucleus have the _____ionization potential , while electrons far from the nucleus have the _______ionization potential.
highest; lowest
What is the octet rule?
Group 1A-7A elements react to achieve an outer shell of 8 valence electrons
What is electronegativity?
a measure of an atom’s attraction for electrons
What is electron affinity?
energy added or released when an electron is added to an atom or molecule
Electronegativity _____ from top to bottom because _____.
decreases; the increasing distance of the valence shell from the nucleus results in a lower attraction between the electrons and the nucleus
Electronegativity _____ from left to right because _____.
increases; the increasing positive charge on the nucleus results in a greater attraction for the valence electrons.
The orbitals get lower in energy as you move from left to right and the atoms hold their electrons tighter; these atoms have a higher first ionization potential.
How is an ionic bond formed?
electrons are transferred from an atom of lower electronegativity to an atom of higher electronegativity
An anion is formed by _____ electrons and is _____ charged.
gaining; negatively
A cation is formed by _____ electrons and is _____ charged.
losing; positively
What is the electronegativity difference between 2 atoms in an ionic bond?
> 1.9
How is a covalent bond formed?
electrons are shared between atoms to complete the atoms’ valence shell
What is bond dissociation entropy/enthalpy?
the amount of energy needed to be absorbed in order to break the bond
What is the electronegativity difference between 2 atoms in a non polar covalent bond?
<0.5
What is the electronegativity difference between 2 atoms in a polar covalent bond?
0.5 to 1.9
In a polar covalent bond, the more electronegative atom _____, and the less electronegative atom _____.
gains a greater fraction of the electrons and has a partial negative charge; has a smaller fraction of the electrons and has a partial positive charge
What is a bond dipole moment?
a measure of polarity of a polar covalent bond; the product of the charge on either atom of a polar covalent bond times the distance between the nuclei
What is formal charge?
the charge on an atom in a polyatomic ion or molecule
How do you calculate formal charge?
formal charge = #ve in neutral, unbonded atom - (all unshared e + ½ shared e)
Why are functional groups important?
- allow us to divide organic compounds into classes
- exhibit characteristic chemical reactions
- serve as a basis for naming compounds
What is an alcohol?
a compound containing an -OH (hydroxyl) group bonded to a tetrahedral carbon atom
What is an amine?
a compound containing a nitrogen atom bonded to one, two, or three carbon atom(s) by single bonds
What is the functional group of both aldehydes and ketones?
a C=O (carbonyl) group
What is an aldehyde?
a compound containing a -CHO group
What is a ketone?
a compound containing a carbonyl group bonded to 2 carbons
What is a carboxylic acid?
Compound containing a -COOH (carboxyl) group
What is an ester?
Derivative of a carboxylic acid in which the H of the carboxyl group is replaced by a carbon
amide
Derivative if carboxylic acid in which the -OH is replaced by an amine
What is VSEPR?
A method for predicting bond angles based on the idea that electrons repel each other and stay as far apart as possible
molecular dipole moment
Vector sum of individual bond dipoles
What 2 things do we need to determine the polarity of a molecule?
1)whether the molecule has polar bonds and 2)what the arrangement of its atoms is in space
