test 1- theory, config., periodic trends, forces Flashcards
Whatre the three bohr postulates
- Atoms have energy levels (shells) for electrons
- When moving within the same shell, electrons do not radiate energy
- When moving between shells, eletrons absorb or emit energy
What is the ground state of an electron, why is it preferred
The lowest energy state of an electron, when it is as close to the nucleus as possible
Doesnt require energy to stay at the energy state, can stay there
What do electrons act like, what do they give off
They can act as waves, not just particles
They give off small energy particles called quanta when moving from higher to lower energy states
Whats the difference between an electron acting as a particle and acting as a wave
When as a particle: it has a definite position and mass, when acting as a wave: it is spread out over a region of space, so the position is uncertain (thats why the orbital is a space where an electron MIGHT be)
Whatre energy levels split into
Subshells and orbitals
Whats a subshell and orbital, what types of subshells are there, how many orbitals are found in each subshell
A subshell is a group of orbitals (s, p, d, f)
An orbital is the region of space occupied by an electron
S subshells hold 1 orbital
P subshells hold 3 orbitals
D subshells hold 5 orbitals
F subshells hold 7 orbitals
Howre orbitals shaped, how many electrons can each of them hold
The shape of the orbitals depend on which subshell it comes from, each can hold two electrons
What do quantum numbers describe, whatre the four types
They describe the orbitals and electrons found in a certain element
Principle quantum (n): which energy level (shell) the electron is found on
Angular momentum (l): which subshell the electron is found on (0=s, 1=p, 2=d, 3=f), l is smaller or equal to the principle number minus one
Magnetic quantum (ml): the orientation of the orbital/ which orbital in the subshell the electron is found on, ml=-l…l
Spin quantum (ms): the spin of the electron/ which of two electrons is on the orbital, can be +1/2 or -1/2
Whats the pauli exclusion principle
No two electrons in the same atom can be described by the same set of quantum numbers
What does an electron configuration describe
How all the electrons are arranged in atomic orbitals for a specific element
Whats the aufban principle
When filling orbitals, the lowest energy orbitals available are filled first
Whats the hunds rule
When orbitals of equal energy are being filled, electrons are most stable when each electron is single occupied before being paired
What is special about elements with d4 or d9 subshells
A filled or exactly half filled d-subshell is especially stable, so an elecctron from the s subshell may move to the unfilled d-subshell
What is atomic radius, how does it increase and decrease on a periodic table, how does the radius change for cations and anions
How far the valence electrons are from the central nucleus
Increases moving down a group, decreases moving left to right across periods
Cations: decreases (grows smaller), anions: increases (grows larger)
What is the shielding effect
Electrons from the inner shells of an atom repel the valence electrons
What is electronegativity and its relationship to atomic radius, how does it increase/decrease on a periodic table
Is the inverse of atomic radius
Is the ability of an atom to draw bonding electrons to itself
Decreases moving down a group, increases moving left to right (more protons=stronger pull on electrons)
How does the shielding effect affect atomic radius and electronegativity/ionization energy
The shielding effect repels the valence electrons further (makes atom larger), it weakens the attractive force between the valence electrons and the nucleus (decreases ionization energy/ makes electronegativity weaker)
How do the periodic trends affect halogens and alkali metals
Alkali metals: largest element in period/ low ionization energy/ less electronegativity (most left= most repulsion)
Halogens: highest electronegativity/ highest ionization energy, smallest element in period (most right= most attraction)
Whatre the three exceptions in the lewis structures
- Elements in group 1, 2, and 13 tend to form compounds when surrounded by fewer than eight electrons (ex. BF3 or BCl3, pay attention to boron)
- Atoms in period 3 or higher can form compounds with more than four other atoms/ use more than eight electrons due to the access of the d orbital (ex. SF6)
- Some compounds can have an odd total number of valence electrons (those molecules are called radicals and are very unstable) (ex. NO2 with 17 electrons in total)
Whatre intramolecular forces and some examples
The bonds within molecules
Ex. Covalent, ionic
How can a bond be formed between atoms, what state is the molecule in after being bonded
When the attractive forces are stronger than the repulsion (the negative electron clouds exert repulsive forces that slow approaching atoms)
In a lower energy state than when they were apart due to their newfound stability
What shapes do ionic compounds form
Crystal lattices
Whats a dipole, whats the difference between a bond dipole and the dipole moment
The separation of electrical charges within a molecule (has a more positive and a more negative end)
Bond dipoles form between each central atom and bonded atom, showing the charges of those parts only
The overall dipole moment indicates the overall charge of the molecule, accounting for symmetry
Whatre lone pairs, how do the ones on the central atom affect the shape/structure/ symmetry/ polarity of the molecule
Lone pairs are the electrons found on the atom thatre not bonded with another atom, they repel the bonded atoms, bending the molecule and making it asymmetrical and therefore polar
What does VSEPR stand for and what does it describe
Valence shell electron pair repulsion
Describes the molecular shape of a molecule, accounting for repulsion
Whatre the three components of axe notation and what does it describe
A= central atom
X=bonding/branching atoms (substituient group)
E=lone pairs on central atom
A writing system used to describe the geometry of molecules based on repulsion (not the actual model, just the writing form)
Whatre the six axe notations, what angles, polarity, and shapes are they
Ax2: linear, nonpolar, 180
Ax3: trigonal planer, nonpolar, 120 (ex. Bf3)
Ax2e: bent, polar, 120
Ax4: tetrahedral, nonpolar,109.5
Ax2e2: bent, polar, about 109.5
Ax3e: trigonal pyramidal, polar, 109.5
Whatre intermolecular forces, whats another name for them
The forces between molecules
Van der waals
Which is weaker: intramolecular, intermolecular
Intermolecular, but they can still be very strong in large numbers
Whatre london forces, howre they formed, what molecules are they found in
Weak, attractive forces that induces a temporary dipole on a nearby atom (by chance, moving electrons within an atom mostly move to one side, causing the atom itself to be polar and causes nearby atoms to also become polar and be attracted)
Found in all molecules, but are most prominent in nonpolar ones because theyre only significant when no stronger forces are present
Whatre dipole dipole forces
Attraction between polar molecules with permanent dipoles
Whatre hydrogen bonds, what atoms can they be formed by
Formed between hydrogen and nitrogen/oxygen/fluorine atoms
The strongest type of dipole dipole attractions
Whyre hydrogen bonds the strongest out of all the intermolecular forces
Nitrogen, oxygen, and fluorine are highly electronegative due to their nuclear charge and small size, pulling the hydrogen’s electrons so strongly that a very strong dipole is created
Howre melting and boiling points of molecules affected by the intermolecular forces
The stronger the intermolecular forces (ex. Dipole dipole, hydrogen bonding), the higher the melting and boiling points due to the amount of energy required to break the bonds
