Random info for Chem
What is the hybridization of the N atom in NH3 ?
The nitrogen atom in NH3 is sp3 hybridized.
VSEPR theory
Valence-shell electron-pair repulsion theory; because electron pairs repel, molecules adjust their shapes so that valence electron pairs are as far apart as possible
Example of expanded octect
XeF2, SF6, IF5
Which of the following is a characteristic of a sigma bond?
a covalent bond
In a Lewis structure, a covalent bond is represented by:
a line
Which of the following will decrease the concentration of a solution?
adding more solvent removing moles of solute
C, N, O, F
always obey the octet rule, cannot have more than 8 electrons in center element
Which of the following stays constant when diluting a solution?
amount of solute
electron pair geometry
arrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons)
The atomic masses on the periodic table are listed in:
atomic mass units
electron deficient molecules
baron and aluminum (form as many bonds as they have valence electrons)
What is used to describe valence electron configurations of atoms and monatomic ions?
lewis symbols
On the resonance hybrid for NO−2, in between the nitrogen atom and each oxygen atom there is:
one covalent bond and one partial bond
The number of atoms in one mole of oxygen is equal to the number of atoms in ______ of hydrogen.
one mole
Which of the following is NOT a molecular structure that can be exhibited by a molecule with tetrahedral electron-pair geometry?
seesaw
What is the hybridization of the oxygen atom in a water molecule?
sp3
Electron structure
the arrangement of electrons in an atom or molecule
theoretical yield
the maximum amount of product that can be produced from a given amount of reactant
actual yield
the measured amount of a product obtained from a reaction
molecular structure
the three-dimensional arrangement of atoms in a molecule
We can predict the number of bonds an atom can form by counting when?
-the number of additional electrons needed to form an octet -the number of valence electrons
How many moles of hydrogen atoms are there in 120 g of C6H12O6?
8.0 moles Hyrdogen
polarity
A lack of electrical symmetry in a molecule. Charge differences on opposite ends of a structure.
Which of the following is equivalent to a mole of carbon atoms?
A mole of carbon atoms is equivalent to 6.022×1023 carbon atoms. In fact, 1 mole of any substance will contain 6.022×1023 items because that is the definition of a mole.
A(n) __________ is used between resonance forms to indicate that the actual structure exists as an average.
Double headed arrow
Which of the following is very reactive and can readily combine with molecules containing atoms with lone pairs?
Electron deficient electrons
The number of electron domains surrounding an atom will determine the
Electron pair geometry
shouldnt have double bonds
Halogens, Flourine
When drawing a Lewis structure for a free radical, which type of atom is more likely to receive the unpaired electron?
Less electronegative element
What is the name of SnO2?
SnO2 is an ionic compound with a tin cation and the oxide anion. Tin can have multiple charges, so the name must indicate the charge with a roman numeral. To find the charge on the tin cation, use the fact that oxide has a charge of −2. There are two oxide anions, so the charge on the tin cation must be +4 in order to give a neutral charge overall. 1(+4)+2(−2)=0. Therefore, the name of the compound is tin (IV) oxide.
If a nitrogen atom has four covalent bonds, what will be its formal charge?
+1
Draw the Lewis structure for SeO2 (selenium dioxide). How many equivalent resonance structures can be drawn that obey the octet rule?
1
Where can you find an incomplete octect most?
B, Al, O, Br covalent compounds in groups 2 and 3 can form stable compounds in which the valence electrons are not in the noble gas structure. However, for these compounds you will find that they do form compounds that minimize formal charge. Hydrogen makes one bond (group 1). Beryllium makes two bonds (it is the only element in group 2 to make covalent compounds). The group 3 elements boron and aluminum make three bonds. How many bonds do carbon (and the other group four elements typically make)? Four.
example of incomplete octect
BI3, BeH2
What bonds have net dipole?
CO, HF
In which molecule are the electron-pair geometry and molecular shape of the same type?
CO2
Which of the following elements is likely to lose two electrons to form a +2 ion?
Ca, group 2
A mole is defined as the number of atoms in an exact mass of which isotope?
Carbon-12
Which of the following is an odd-electron molecule?
ClO2, ClO2 is an odd-electron molecule (7+12=19).
Lone pairs present in trigonal bipyramidal electron-pair geometry always occupy which position?
Equatorial
formal charge
The number of valence electrons in an isolated atom minus the number of electrons assigned to the atom in the Lewis structure
Free radical
an atom or a group of atoms that has one unpaired electron
SI, P, S, Cl
can have expanded octect/more than 8 electrons
Which of the following is a step in predicting electron pair geometry and molecular structure using VSEPR theory?
count the number of regions of electron density around the central atom write the Lewis structure of the molecule use the number of lone pairs to determine the molecular structure identify the electron-pair geometry based on the number of regions of electron density
When drawing a Lewis structure, the first step is to:
determine the amount of valence electrons
The ________ describes the location of electrons and the ________ describes the location of atoms.
electron-pair geometry, molecular structure
nonpolar
equal sharing of electrons, symmetry
node
pi bond
Which of the following is named using the unmodified element name and adding the word "ion"?
simple cations
We can predict the number of bonds an atom can form from:
the number of electrons needed to form an octet
net dipole
the overall direction of partial negative charge in a molecule
Which of the following produces sigma bonds?
the overlap of an s and p orbital the overlap of two s orbitals the end-to-end overlap of two p orbitals direct orbital overlap
If we compare a mole of carbon atoms to a mole of oxygen atoms, which sample will contain more atoms?
they will contain same, they will both contain precisely avogadro's number of atoms.
expanded octet
when a molecule has more than 8 electrons around the central atom. Sulfur, phosphorus, silicon, and chlorine are common examples of elements that form an expanded octet
dipole moment equation
µ= q•d
A hybridized atomic orbital can contain or participate in which of the following?
σ-bonds lone pairs of electrons single unpaired electrons (radicals)
Which of the following is a step in creating a Lewis structure?
-Place all remaining electrons on the central atom. -Draw a skeleton structure of the molecule around the central atom. -Rearrange electrons of the outer atoms to make multiple bonds with the central atom.
triple bond
A chemical bond formed when atoms share three pairs of electrons
double bond
A chemical bond formed when atoms share two pairs of electrons
Which of the following is an example of a chemical (as opposed to physical) change?
A chemical change results from a chemical reaction, while a physical change is when matter changes forms but not chemical identity.
6.022×1023 is known to be the number of entities composing a mole. This fundamental constant is known as:
Avogadro's constant
Hybridization
Breeding technique that involves crossing dissimilar individuals to bring together the best traits of both organisms
Which molecule will have no net dipole?
CCl4
What is the hybridization of the C atom in CF4 ?
CF4 has a tetrahedral structure and carbon in it has a hybridization of sp3. 7
Lewis structures are limited because they do not display the __________.
Correct bond angles In the molecule
nonpolar molecules
Electrically balanced molecules. Look for symmetry if there is an element around it it isnt polar. N2, O2, Cl2, F2, H2, He, Ne, Ar, Xe, Ch4, C2H6, Ch2=Ch2
Molecular geometry VS electron geometry
Electron geometry teaches us about the arrangement of different electron groups. Molecular geometry, on the other hand, helps us understand the entire atom and its arrangement. We consider both lone electron pairs and bond electron pairs while determining the shape of a molecule in electron geometry. In molecular geometry, though, we only consider bond electron pairs.2. We calculate the number of total electron pairs in electron geometry and not in molecular geometry.3. Through electron geometry, we get the spatial arrangement of the lone pairs and bond in the molecule. We can determine it through VSEPR theory, according to which, electron domains repel each other.
VSEPR theory considers which of the following?
Electron pair repulsion. The VSEPR theory assumes that each atom in a molecule will achieve a geometry that minimizes the repulsion between electrons in the valence shell of that atom. ... Repulsion between these pairs of electrons can be minimized by arranging them so that they point in opposite directions.
Which of the following statements about hybridization are true?
Hybrid orbitals within the same atom have the same energy and shape. Hybrid orbitals are described mathematically as a linear combination of atomic orbitals. An atom can have both hybridized and unhybridized orbitals at the same time.
Cant have expanded octect
Li, Be, B, C, N, O, F
polar molecules
Molecules that have an unequal distribution of charges, partialy charges molecule. H-N, O, F, H2O, Nh3,HF, CH3OH, CH3NH2, CH3COOH
Which of the following values for the principal quantum number corresponds to elements that can accommodate more than four pairs of electrons with other atoms?
N> 3
If there are multiple resonance structures of a molecule with a formal negative charge that can end up on different atoms, placing the negative formal charge on which of the following elements generally gives the most stable resonance structure?
O, The negative charge is most stabilized when it is on the most electronegative atom. Of the above options, that would be oxygen.
Which bond in phosphoryl chloride, shown above, is the "largest"
P=O
Which of the following does NOT have trigonal planar electron-pair geometry?
PCl3
unhybridized
Pi bonds consist of (Hybridized/Unhybridized) orbitals
What statement is NOT correct about σ bonding?
Rotation around single σ-bonds does not occur easily.
Hypervalent molecules require that central atoms access:
S,p, and d
What will be the molecular geometry for a molecule with a central atom that has five regions electron density if one of the regions of electron density is a lone pair?
Seesaw
Hypervalent atoms
Share more than four Pairs of electrons Ex) P, S, Xe
Steric number
Steric number is the number of atoms bonded to a central atom of a molecule plus the number of lone pairs attached to the central atom. The steric number of a molecule is used in VSEPR
What is a exception to the octet rule?
Sulfur in SO2−4
Which of the following statements about deciding between resonance structures with formal charges is correct?
The molecular structure where all formal charges are zero is preferred.
When calculating the concentration of a diluted solution using the equation M1V1=M2V2 (also sometimes given as c1V1=c2V2), what must be true about the units of volume?
V1 and V2 can be any volume units, as long as they are the same.
The reason that atomic numbers are always integer values is because every element has:
a particular number of protons
A molecule contains a central atom from Group 13 in the second row of the periodic table. The molecule shows none of the characteristics of a free radical, but will often form bonds with other molecules by accepting a pair of electrons. This molecule is most likely:
an electron-deficient molecule As the central atom of this molecule is in the second row of the periodic table, we know that it cannot be hypervalent. We also know that it cannot have an odd number of electrons, as experimental evidence suggests that it is not a free radical (as all odd-electron molecules are). It is most likely electron-deficient due to the location of its central atom (Group 13) and its tendency to form bonds with molecules containing lone pairs of electrons.
In a resonance structure for NO−3, nitrogen has single bonds to two of the oxygens and a double bond to one of the oxygens. In a resonance hybrid structure, what will the nature of the bonds be?
between one or two bonds
A Lewis symbol with no dots must be a:
cation
What is the relationship between dipole moment and the distance between the charges?
directly proportional, The further away the partial charges are, the longer the vector will be that represents the resulting dipole, and a longer dipole means a stronger dipole.
Which of the following is NOT a step in constructing Lewis structures?
draw a skeletal structure with the most electronegative atom in the middle
What is true about the covalent bonds in the nitrite ion, NO−2?
equal length, Even though each resonance structure shows one single bond and one double bond, these are actually of the same length in the actual molecule.
In order to maintain accuracy, valence bond theory must include which component?
hybridization
Molecular geometry
is the three-dimensional arrangement of the atoms that constitute a molecule. It includes the general shape of the molecule as well as bond lengths, bond angles, torsional angles and any other geometrical parameters that determine the position of each atom.
A pi bond involves:
lateral orbital overlap side-by-side, or lateral orbital overlap with the electron density concentrated on opposite sides of the internuclear axis. lateral overlap of p orbitals overlap of unhybridized orbitals
Bond angles decrease as more lone pairs are added because
lone pairs repel other electron densities slightly more than bonding pairs
The observation that an atom has slightly less mass than the sum of the masses of its subatomic particles is called which of the following?
mass defect. Ex)the nucleus of a helium atom is composed of two neutrons and two protons. The sum of the masses of two neutrons and two protons is 4.03298 amu, while the actual mass of a helium nucleus is found to be only 4.00260 amu. The difference (in this case, 0.03038 amu) is the mass defect for helium. The energy corresponding to the mass defect, using the equation E=mc2, is referred to as the nuclear binding energy.
When naming binary covalent compounds, the element listed first will be the one that is
more metallic
In order for a molecule to be polar, it must have?
net dipole, polar covalent bonds, and asymettrical
If an atom has a full octet, it will have:
noble gas electron configurations
binary covalent compounds
nonmetal and nonmetal
Resonance Form
one of a number of valid Lewis structures for a particular molecule
resonance structure
one of the two or more equally valid electron dot structures of a molecule or polyatomic ion
Electrons on a Lewis symbol will be arranged:
one on every side before placing a second on any side
The individual Lewis structures of resonance are known as:
resonance forms
When diluting a solution, which of the following changes?
solution volume solution concentration liters of solvent
In a chemical equation, the number of atoms of a particular element that are present in a substance is indicated by a:
subscript
Resonance hybrid
the actual structure of a molecule that is intermediate between two or more resonance structures
resonance hybrid
the actual structure of a molecule that is intermediate between two or more resonance structures
How to find dipole moment of a molecule?
the dipole moment is calculated to be 1.85 D by multiplying the distance between the oxygen and hydrogen atoms by the charge difference between them and then finding the components of each that point in the direction of the net dipole moment
The sum of the average atomic masses of all the atoms present in a substance's formula is known as:
the formula mass (molecular mass)
valence bond theory
the idea that covalent bonds are formed when orbitals of different atoms overlap
percent yield
the ratio of the actual yield to the theoretical yield expressed as a percent
A mole of one element contains _______ number of atoms as a mole of another element.
the same
Which bond is strongest in a carbon-carbon triple bond?
the sigma bond
limiting reactant
the substance that controls the quantity of product that can form in a chemical reaction
Molecular structure
the three-dimensional arrangement of atoms in a molecule
molecular polarity
the uneven distribution of molecular charge
A molecule that can be described by multiple resonance forms:
will have an electronic structure that is an average of the resonance forms
How many molecules are in 3 moles of benzene?
1.807x 10^24. Since a mole is a fixed amount, simply multiply the number of molecules in a mole, 6.022×1023, by the number of moles, 3, in order to determine the number of molecules in 3 moles.
A molecule with square planar geometry but with six electron regions has ______ lone pairs.
2
How many bonds would oxygen need to form to obtain an octet?
2
How many bonds would nitrogen need to form to obtain an octet?
3
How many grams of helium are in a balloon with 8.40 mol of helium atoms?
33.6 g
According to VSEPR theory, electrons in the valence shell of a central atom form __________.
4
Four atomic orbitals will combine to give how many hybrid orbitals?
4
Which of the following statements are true?
The sum of all formal charges in a neutral molecule must be zero. The sum of all formal charges in an ion must equal the charge of the ion. Small (or zero) formal charges on individual atoms are better than large ones. When formal charge cannot be avoided, negative formal charge should reside on the most electronegative atom.
The elements that are most likely to have multiple oxidation states are?
Transition metals. Oxidation state of an element in a given compound is the charged acquired by its atom on the basis of electronegativity of other atoms in the compound.
Which spatial orientation will involve more than one bond angle value?
Trig bipyramidal
Which type of bond takes up the largest region of space?
Triple bond
Can a nonpolar molecule can contain polar bonds?
True
