Ch. 1: General Chemistry Flashcards
What is the charge of an atom’s nucleus?
positively charged, the nucleus contains protons and neutrons
How do you calculate the number of electrons in an atom?
= proton number - charge number
How do you calculate the number of protons in an atom?
the atomic number
What does the mass number of an atom represent
the number of protons + neutrons
What is an isotope?
two or more forms of the same elements that have the same number of protons but different number of neutrons
How do you calculate molecular mass?
the sum of the atomic masses of all atoms in the molecule
What are degenerate orbitals?
orbitals that have the same energy, like the 2p orbital has three degenerate p atomic orbitals
What’s the Pauli Exclusion Principal?
no more than two electrons can occupy each atomic orbital, and the two electrons must be of opposite spin
What is Hund’s Rule?
when there are two or more atomic orbitals with the same energy, an electron will occupy an empty orbital before it will pair up with another electron
What is an atoms ground-state electronic configuration?
When an atom’s electrons are are all in the available orbitals with the lowest energy
Describe the aufbau principle.
an electron always goes into the available orbital with the lowest energy
What does it mean for an element to be electronegative?
the element readily acquires an electron (F>O>N>C)
What’s the difference between a nonpolar and polar covalent bond?
If the eneg difference between the bonded atoms is less than 0.5, then is nonpolar
If the eneg different between the bonded atoms is between 0.5 and 1.9, then is polar
What’s the pattern of electronegativity on the periodic table?
goes toward the upper left corner of the PT
What’s the pattern of electron affinity on the periodic table?
goes toward the upper left corner of the PT
What’s the pattern of atomic radius size on the periodic table?
goes toward the bottom right corner of the PT
What’s the pattern for reactivity on the periodic table?
goes toward the bottom right corner of the PT
What’s the pattern for ionization energy on the periodic table?
goes toward the upper left corner of the PT
How do you calculate formal charge?
formal charge = (valence electrons) - [(the number of lone-pair electrons) + the number of bonds)]
What are the steps for drawing lewis structures?
- determine the total number of valence electrons
- distribute the atoms
- form bonds and fill octets with lone-pair electrons
- assign a formal charge
What’s a kekulé structure?
like lewis structures except lone pairs are omitted
What’s a skeletal structure?
show the C-C bonds as lines, and don’t show the carbons or hydrogens bonded to the carbons
What is the Heisenberg uncertainty principle?
both the precise location and the exact momentum of an atomic particle cannot be simultaneously determined, we can never say precisely where an electron is – we can only describe its probable location
What is a node?
A region of an orbital where the probability of finding an electron falls to zero. Nodes occur because of the wave-like properties of an electron
What shape is an s orbital?
spherical
What is the shape of a p orbital?
dumbbell shaped, with a nodal plane passing through the center of the nucleus (b/w the two lobes)
Describe molecular orbital theory.
Schrodinger and DeBroglie came up with a model that suggests every electron corresponds with a wave function and an electron moves around the nucleus in a standing wave
What is a sigma bond?
the strongest type of covalent bond, formed by the overlap of atomic orbitals, an end on overlap
What is a pi bond?
an overlap of p orbitals in a side-by-side arrangement
Describe bonding molecular orbitals
Electrons that spend the majority of their time between the nuclei of two atoms are placed into bonding orbitals, and the molecule is stabilized
What is constructive combination in MO?
Thinking about the wave-like properties of electrons, combining waves can lead to constructive interference and can produce regions with a higher probability of electron density
What is destructive combination in MO?
Thinking about the wave-like properties of electrons, combining waves can lead to destructive interference and can produce nodes, or regions of no electron density
How do you construct and fill in a molecular orbital diagram?
this is for diatomic molecules, switch for B2, C2, and N2 because that follows hybridization. the MO diagram is filled according to Hund’s Rule and the Aufbau principle
How do you calculate bond order and what is its relationship to MO theory?
In MO theory, stability of a covalent bond is related to its bond order
BO = 1/2[(bonding electrons) - (antibonding electrons)]
if BO = 0, then no bond can form because the molecule is too unstable
VSEPR: zero lone pairs, steric number of 2
linear, 180 bond angle, sp
VSEPR: zero lone pairs, steric number of 3
trigonal planar, 120, bond angle, sp2
VSEPR: one lone pair, steric number of 3
bent, <120 bond angle, sp2
VSEPR: zero lone pairs, steric number of 4
tetrahedral, 109 bond, angle, sp3
VSEPR: one lone pair, steric number of 4
trigonal pyramidal, <109 bond angle, sp3
VSEPR: two lone pairs, steric number of 4
bent, «109 bond angle, sp2
VSEPR: zero lone pairs, steric number of 5
trigonal bipyramidal, 120 and 90 bond angles, sp3d
VSEPR: zero lone pairs, steric number of 6
octahedral, 90 bond angle, sp3d2
VSEPR: one lone pair, steric number of 5
seesaw, <120 and <90 bond angles, sp3d
VSEPR: two lone pairs, steric number of 5
t-shape, <90 bond angle, sp3d2
VSEPR: three lone pairs, steric number of 5
linear, 180 bond angle
VSEPR: one lone pair, steric number of 6
square pyramid, <90 bond angle, sp3d2
VSEPR: two lone pairs, steric number of 6
square planar, 90 bond angle, sp3d2
VSEPR: three lone pairs, steric number of 6
t-shape, 90 bond angle, sp3d
VSEPR: four lone pairs, steric number of 6
linear, 180 bond angle
Explain the concept of hybrid orbitals.
They are formed by the linear combination of the atomic orbitals. Hybrid orbs are favored because they’re more directional which leads to greater overlap when forming bonds, therefore the bonds formed are stronger and so more stable compounds are created
How do you know what a molecule’s hybridization is?
Count the number of atoms bonded to it and the number of lone pairs. Double and triple bonds still count as being only bonded to one atom.
Why is the anti-bonding orbital positioned higher on a molecular orbital diagram than the bonding orbital?
Because if an electron is in the anti-bonding region then it actually adds to the repulsing forces and pushes the two nuclei apart and leads to having a higher potential energy
Explain the hybridization in C2H4
for each C, one 2s orbital and two 2p orbitals hybridize to form 3 sp2 orbitals. This leaves one unhybridized p orbital left over (because the p subshell has three orbitals and only 2 are being used for sp2). Therefore, for each C, 2 sp2 s bond to 2 Hs, and the p orbital and the last sp2 create a double bond between the carbons.
Explain the shape of sp3 orbitals and how it creates single bonds.
four hybrid orbitals are formed, has two lobes that differ in size because the s orbital adds to one lobe of the p orbital and subtracts from the other lobe
the larger lobe is used to form covalent bonds and its more stable than a p orbital and less stable than an s orbital
Explain the shape of sp2 orbitals and how it creates double bonds
three hybrid orbitals are formed and there’s one unhybridized p orbital
the double bond results from side-to-side overlap of the two unhybridized p orbitals
What does a double bond consist of?
1 sigma + 1 pi
What does a triple bond consist of?
1 sigma + 2 pi
What does a single bond consist of?
1 sigma
Explain the shape of sp orbitals and how it creates single bonds
two sp hybrid orbitals are formed and there’s two unhybridized p orbitals
Explain the bonds in ammonia(NH3).
4 hybrid sp3 orbitals are formed, three are used for bonding with H, and the other is a lone pair of electrons which takes up more space than a bonded pair
Explain the bonds in the ammonium ion(+NH4)
Since the ion doesn’t have any lone pairs, the molecular geometry is tetrahedral and has bond angles of 109.5
Explain the bonds in water.
Oxygen hybridizes four sp3 orbitals because it forms two bonds and has two lone pairs. Two of the orbitals bond with the s orbitals of H, and the other two have lone pairs occupying them. The molecule has a bond angle of 104.5
Explain the bond in a hydrogen halide.
Halogens form 4 hybrid orbitals with only one unpaired valence electron so they only form one covalent bond. Also, the electron density in the region of orbital overlap decreases as the size of the halogen increases.
Explain paramagnetism.
Attraction to a magnetic field caused by unpaired electrons in an orbital diagram. Due to their spin, unpaired electrons have a magnetic dipole moment.
Explain diamagnetism.
paired electrons in an orbital diagram
