Exam 1 Flashcards
What is avogadro’s number?
6.022 x 10^23
What is the conversion from Celsius to Kelvin?
K = degrees C + 273.15
In terms of grams, how much are megagrams?
1 x 10^6 (1,000,00)
In terms of grams, how much are micrograms?
1 x 10^-6 (0.000001)
What is the formula for density?
d = m/v (mass/volume)
What is a mixture?
A physical combination of two or more substances
What are the two types of mixtures?
Hetergeneous and homogeneous
What is a compound?
A substance composed of two or more elements that are chemically united in fixed proportions
How can a mixture be separated?
Through physical means
How can a compound be separated?
Through chemical means
What is accuracy?
How close a measurement is to its true value
What is precision?
How closely multiple measures are to to one another
What are isotopes?
Atoms of an element with the same number of protons but different number of neutrons
What does the quantum mechanical model describe?
It describes the energy of an electron in atom
What is the Heseinberg Uncertainty Principle?
It is impossible to know both the position and momentum of a particle with certainty
What is a shell?
Example: 1s or 2s2p or 3s3p3d
What is a subshell?
Example: 2s or 2p or 3d
What is an orbital?
Example: 2s has two orbitals or 2p has three orbitals
What is the principle quantum number?
It determines the size (n=0,1,2…)
What is the angular momentum quantum number?
It determines the shape and volume (l=0,1,2…)
What is the magnetic quantum number?
It determines which orbital an electron is in (ml=-2,-1,0,1,2…)
What is the shape of the s orbital?
Spherical
What is the shape of the p orbitals?
Dumbbell
What is the shape of the d orbitals?
4-leaf clovers
How many orbitals are in the s, p, d, and f orbitals?
s: 1 orbitals
p: 3 orbitals
d: 5 orbitals
f: 7 orbitals
What is the electron spin quantum number?
Determines the spin of an electron (ms=-1/2,1/2)
What is the Pauli Exclusion Principle?
No electron in an atom can have the same four quantum numbers
How many electrons can an orbital hold?
2 electrons
What orbital do these quantum numbers represent:
n=1
l=0
ml=0
s orbital
What orbital do these quantum numbers represent:
n=2
l=1
ml=-1,0,1
p orbital
What orbitals do these quantum numbers represent:
n=3
l=2
ml=-2,-1,0,1,2
d orbital
What orbitals do these quantum numbers represent:
n=4
l=3
ml=-3,-2,-1,0,1,2,3
f orbital
What are degenerate orbitals?
Orbitals with the same energy level
What is the relationship between how close an electron can get to the nucleus and the amount of energy it has?
The closer an electron can get to the nucleus, the more stable it is, and the lower the energy it has
What is the Hund’s Rule?
In a set of degenerate orbitals, the number of unpaired electrons with the same spin is maximized
What are exceptions to electron configuration?
Chromium: greater stability with a half-filled 3d subshell
Copper: greater stability with a fully-filled 3d subshell
What is shielding?
Inner electrons block outer electrons from nuclear charge
What is nuclear charge?
The positive charge present in the nucleus of an atom
What is effective nuclear charge?
The nuclear charge an electron actually experiences
What is the trend for effective nuclear charge?
It increases across the period and down the group
Why does effective nuclear charge increase across the period?
The number of core electrons stays the same as the number of protons and valence electrons increase
Why does effective nuclear charge increase down the group?
It increases less significantly than across the period because it is offset by the increase in core electrons
What is atomic radius?
The distance between the nucleus of an atom and its valence shells
What is the trend for atomic radius?
It decreases across the period and increases down the group
Why does atomic radius decrease across the period?
Effective nuclear charge increases across the period therefore those valence electrons are experiencing more of the nucleus’ pull and thus pulled closer
Why does atomic radius increase down the group?
The principle quantum number increases down the group which means there is a whole new set of core electrons
What is ionization energy?
The energy required to remove an electron from a gaseous atom
What is the trend for ionization energy?
It increases across the period and decreases down the group
Why does ionization energy increase across the period?
Electrons are pulled more tightly to the nucleus of an atom as you go across the period, making it harder to remove said electrons
Why does ionization energy decrease down the group?
It is easier to remove the valence electrons from bigger atoms because they are so far away from the nucleus
What do atoms with low IE tend to form?
Cations (positively charged ions)
What do atoms with high IE tend to form?
Anions (negatively charged ions)
What IE do noble gases have?
Very high IE because they do not want to ionize
What the exceptions in the IE trend?
Nitrogen has a higher IE than oxygen because oxygen has one set of paired electrons in its 2p orbital, which means there are more electron-electron repulsions, making it easier to remove one of the electrons in the pair. Beryllium has a higher IE than boron because boron has one electron in its p orbital and because the p orbital is further away from the nucleus, it is easier to remove it.
What is the relationship between first ionization energy and second ionization energy?
In second ionization energy, it becomes more difficult to remove another electron.
How much energy does it require to remove a core electron?
It requires a large amount of energy because those core electrons are closer to the nucleus and will experience a greater effective nuclear charge
What is electron affinity?
The negative (-1x) of the energy change that occurs when an electron is accepted by an atom in the gaseous state
What is the favorable value for electron affinity?
Large and positive values
What do atoms with low EA tend to form?
Cations
What do atoms with high EA tend to form?
Anions
What is the trend for electron affinity?
It increases across the period and decreases down the group
Why does electron affinity increase across the period?
Since effective nuclear charge increases across the period, an electron can be more easily added because it will feel more of the nuclear’s charge (also the atoms to the right of the periodic table want to gain a noble gas configuration)
Why does electron affinity decrease down the group?
The atoms are much bigger and therefore will not experience that much of the nuclear’s charge and will instead want to remove an electron, not add one
What is an exception to EA trend (F)?
Cl has a greater EA than F because it Cl is bigger than F and has a bit more space to add an electron
What is an exception to EA trend (Group 2)?
Group 1 has higher EA than group 2 because it is easier to add an electron to an s orbital rather than a p oribital
What is an exception to EA trend (Group 5)?
Group 4 has a higher EA than group 5 because within the p subshell, it is easier to add an electron to an empty orbital than to add one to an orbital that already contains an electron
What is the trend for metallic behavior?
It decreases across the period and increases down the group
When a cation is formed, which electron is removed first?
The electron is removed first from the highest value of ns orbital and then from the (n-1)d orbitals; for example, remove from 4s first than from 3d
What does isoelectronic mean?
An ion with the same electron configuration as a noble gas
What is ionic radius?
The radius of a cation or anion