Chem exam 2
lewis symbol for Li
!s^2, 2s^1 --> valence electron
Covalent compound prefixes
1- mono 2- di 3- tri 4- tetra 5- penta 6- hexa 7- hepta 8- octa 9- nona 10- deca 12- dodeca
Write formulas for covalent compounds.
1. All atoms present are indicated 2. A subscript number is used to indicate & identify the number of atoms of each element that are present CH4 → the subscript is the number of hydrogens present 3. Chemical formula always shows whole number ratios of elements C6H12O6 → ^ & 12 are whole numbers 4. Know the difference between empirical formula, molecular formula, and structural formula C3H6 → molecular formula CH2→ empirical formula H2-C=C-C-H3 → structural formula
Understand Lewis structures for molecules and know exceptions to octet rule.
1. Count valence electrons for each atom 2. Draw the framework: which is the central atom? (usually element with lowest subscript) 3. Add bonding pairs of electrons (2 electrons per bond) 4. Add nonbonding electrons 5. Count how many electron you have used 6. If you haven't used all electrons; assign remaining electron as nonbonding pair on the inner atoms
Write formulas for ionic compounds compounds
1. The cation/anion ratio must give a net charge of 0. 2. A cation must always be listed before the anion (Na+, Cl-) → NaCl 3. The formula of the polyatomic ion is written as a unit 4. Polyatomic ions are placed in parentheses with a following subscript when the number of polyatomic ions in the formula is greater than one. Cu2+, OH- → Cu2+ , 2OH => Cu(OH)2
Electron configuration example Na
11Na- 1s^2, 2s^2, 2p^6, 3s^1 or [Ne]3s^1
Electron configuration example Cl
17Cl- 1s^2, 2s^2, 2p^6, 3s^2, 3p^5 or [Ne]3s^2 3p^5
Electron configuration example K
19K- 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^1 or [Ar]4s^1
electron configuration levels
1s(2) --> 2s(2) --> 2p(6) --> 3s(2) --> 3p(6) --> 4s(2) --> 3d(10) --> 4p(6) --> 5s(2)-- 4d(10) --> 5p(6) --> 6s(2) --> 4f(14) --> 5d(10) --> 6p(6) --> 7s(2) --> 5f(14) --> 6d(10)
lewis symbol for Be
1s^2, 2s^2 --> 2 valence electrons
lewis symbol for B
1s^2, 2s^2, 2p^1 --> 3 valence electrons
lewis symbol for N
1s^2, 2s^2, 2p^3 --> 5 valence electrons
lewis symbol for F-
1s^2, 2s^2, 2p^6 --> 8 valence electrons
lewis symbol for Ne
1s^2, 2s^2, 2p^6 --> 8 valence electrons
write electron configuration for transition metal for Fe
26Fe- 1s62, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^6 —> 1s62, 2s^2, 2p^6, 3s^2, 3p^6, 3d^8, 4s^0
write electron configuration for transition metal for ion Cu2+
27Cu^2+: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^10, 4s^1 —-> 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^9, 4s^0
write electron configuration for transition metal for Cu
29Cu- 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^9 —> 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 3d^10, 4s^1
write electron configuration for transition metal for ion Br-
36Br-: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^5 —> 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^6
Write electron configuration for Te & give number of valence electrons. What is the effective nuclear charge for Te atoms?
52Te: 1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^10, 4p^6, 5s^2, 4d^10, 5p^4 Valence electrons= 6 Core electrons= 46 Z*eff= 52-46= 6
Why is the ionization energy of B lower than Be?
5B→ 1s^2, 2s^2, 2p^1 4Be→ 1s^2, 2s^2 B ionization energy is lower because B has an unpaired electron in 2p^1 so the electron can easily be taken away unlike in Be because its orbitals are full so it would be hard to remove an electron
Why does oxygen have a lower IE than N?
7N--> 1s^2, 2s^2, 2p^3 8O--> 1s^2, 2s^2, 2p^4 N has one arrow at a higher energy level than oxygen with two arrows, because oxygen's electrons are repulsing causing the orbital to be unstable and move down to a lower energy level. Oxygen at a lower energy level makes it more likely to lose an electron than Nitrogen.
Why does N have a lower EA than C?
7N→ 1s^2, 2s^2, 2p^3 / 6C → 1s^2, 2s^2, 2p^2 N has less tendency to accept another electron because the 2p'^3 orbital is half full compared to C's 2p^2 orbital which is not half filled.
What is the formula for aluminum nitride?
Al(NO2)3 → 3 nitrite ions are needed to provide a total of -3 charge to balance +3 from Al
Naming Acids
Always start with the prefix hydro-, followed by the suffix (base name of nonmetal) "ic" and is followed by the word acid Ex:HBr= hydrobromic acid
Understand trend in atomic size
Atomic size- Atomic size increase from top to bottom and from right to left on the periodic table Examples: TE is greater than S, Te is greater than Xe.
Bond Polarity and how to identify the types of bonds, and how it subsequently evolves into dipole moments.
Bond polarity is the electronegativity of the bonded atoms. The dipole is the measurement of the polarity of a bond. Bonds that are more electronegative pull the other electrons to them.
What is the name of this hydrocarbon, C10H22
C10H22= decane (dec=10)
What is the formal charge of C2H4O2?
C2H4O2 → 24 e- FC(H1)= 1-0-2/2= 0 FC(H2)= 1-0-2/2= 0 FC(H3)= 1-0-2/2= 0 FC(H4)= 1-0-2/2= 0 FC(C1)= 4-0-8/2= 0 FC(C2)= 4-0-8/2= 0 FC(O1)= 6-4-4/2=0 FC(O2)= 6-4-4/2=0
What is the name of this hydrocarbon, C2H6
C2H6= ethane (eth=2)
What is the name of this hydrocarbon, C3H8
C3H8= propane (prop=3)
What is the name of this hydrocarbon, C4H10
C4H10= butane (but=4)
What is the name of this hydrocarbon, C5H12
C5H12= pentane (pent=5)
What is the name of this hydrocarbon, C6H14
C6H14= hexane (hex=6)
What is the name of this hydrocarbon, C7H16
C7H16= heptane (hept=7)
What is the name of this hydrocarbon, C8H18
C8H18= octane (oct=8)
What is the name of this hydrocarbon, C9H20
C9H20= nonane (non=9)
What is the bond polarity of CCl4
CCl4 C= 2.5, Cl=3.0 3.0-2.5= 0.5, nonpolar covalent bond From C arrow point toward Cl; arrows in four different directions cancel out μD= 0; CCl4 is a nonpolar molecule
What is the formal charge of CH2O3?
CH2O3 → 24 e- FC(H1)= 1-0-2/2=0 FC(H2)= 1-0-2/2=0 FC(O1)= 6-4-4/2= 0 FC(O2)= 6-4-4/2= 0 FC(O3)= 6-4-4/2= 0 FC(C)= 4-0-8/2= 0
What is the name of this hydrocarbon, CH4
CH4= methane (meth=1)
What is the bond polarity of CHCl3
CHCl3 C=2.5, H=2.1, Cl=3.0 Arrows point from C to Cl and from H to C, arrows don't cancel out μD=1.04; CHCL3 is a polar molecule
What is the formal charge of CO?
CO → 10 e- :C ≡ O: FC= V - N - B/2 FC(C)= 4-2-6/2= -1 FC(O)= 6-2-6/2= +1
What is the bond polarity of CO2?
CO2 O=C=O (linear structure) Arrows point from C to O because O has a higher electronegativity, arrows cancel out μD=0; CO2 is a nonpolar molecule
What is the resonance structure of CO3-
CO3- :O: = C - ::O:- → -::O: - C = :O:
What is the name of the compound with the formula CuCN?
Copper (I) cyanide → the name of this compound includes the charge on the cation in roman numeral with parentheses
What is Coulomb's law? Definition and relationship.
Coulomb's law is the strength of the force between two charged particles together in the same material is proportional to the product distance between them F ⋉Qa x Qb / r^2ab --> F= K x (q(a) x q(b)/ r^2ab) F= force q= electron charge K= proportional constant ⋉ = proportional r(ab)= distance between particle a & b
Classify the size of Cu, Cu+, Cu2+
Cu= 29, Cu+= 28, Cu2+= 27 Cu2+ < Cu+ < Cu
Understand trend in electron affinity.
Electron affinity is always negative. EA increases from the bottom to the top of the periodic table and increases from left to right.
Understand electronegativity and how it arises.
Electronegativity is unequal electron sharing and is the ability of an atom to attract bonding electrons and it arises from differences in effective nuclear charge. Unequal electron sharing leads to asymmetric bonding electron density. The difference in electronegativity between atoms in a compound can let you know if the compound is molecular or ionic Delta X= X2- X1 If Delta X < or equal to 0.5 → nonpolar covalent bonds If Delta X < 0.5 -2.0 → polar covalent bonds If Delta > or equal to 2.0 → ionic bond
Valence electrons
Electrons occupying the highest principal quantum number & incomplete d & f orbitals.
Paramagnetic
Elements are attracted to a magnetic field due to having at least one orbital with an unpaired electron Ex. <> < <
Diamagnetic
Elements are not attracted by the magnetic field due to having all spin-paired electrons Ex. <> <> <>
Know how to write electron configurations for transition metals.
For transition metals the higher principle quantum number shell gives its electrons and moves above to the higher orbital type with a lower principle quantum number in the electron configuration
Know how to calculate formal charges
Formal charges formula: FC= V - N - B/2 FC= formal charge, V= valence electrons, N= # of nonbonding electrons, B= total # of shared electrons in bonds Lower formal charges= more stable the molecular structure is
What is the bond polarity of H2O
H2O O=3.5 H=2.1 H-:o:-H (bent structure) Arrows point from H towards O; when added up arrow points up straight through middle of molecule; water is a polar molecule
What is the resonance structure of H2PO4-?
H2PO4- :O: = P - ::O:- → -::O: - P = :O:
What is the electronegativity of HF?
HF → X(H)= 2.1, X(F)=4.0 (F) 4.0 - (H) 2.1= 1.9 → polar covalent bond H 1 → 7 F
Define ionic and covalent bonds and give the difference among the two.
Ionic bonds: the electrical energy between charged spaces due to the transfer of electrons from a metal & nonmetal Covalent bonds: the sharing of 2 electrons between two nonmetal atoms
Define ionic and covalent compounds and give the difference among the two.
Ionic compounds: are formed between a metal and a nonmetal, and are composed of cations and anions Ex. NaCl → Na+ and Cl- Covalent compound: are formed between nonmetals Ex. H2O → H2+ and O2- Binary compound: are compounds that consist of only 2 elements Ex. NH3 —> N3- and H3+
Understand trend in ionization energy
Ionization energy values are always positive, the larger the IE the harder it is to remove. IE increases from the bottom to the top of the periodic table and increases from left to right.
Define isoelectronic.
Isoelectronic: atoms or ions that have the same number of electrons Ex. 10Na+, 10Ne, 10F-
Know electron configuration for elements and the rules to go by (Aufbau Principle, Pauli Exclusion Principle, Hund's Rule of Maximum Multiple.
It's the arrangement of electrons in the orbits of an atom. It consists of symbols that contain 3 pieces of information: principle quantum number shell (n), the letter that tells you the orbital type (s, l, m), the subscript number that tells you the number of electrons in that particular shell (1s^2). Aufbau principle is to determine the electron configuration for an atom, we add a number of electrons equal to its atomic number. Beginning with hydrogen, and continuing across the periodic table we add one electron to each subshell of lowest available energy first. Pauli Exclusion Principle is that no two electrons can have the same set of quantum numbers. Hund's Rule is that degenerate orbitals are filled with electrons one by one filled before electron pairing occurs. Ex. 6C- 1s^2: <> 2s^2: <> 2p^2: < < Ex. 8O- 1s^2: <> 2s^2: <> 2p^4: <> < <
Ionization energy
It's the energy required to remove an electron from a gaseous atom
Ferromagnetic
Materials contain particles with unpaired electrons on it; very attracted to magnetic field
Why do we say, metals are electropositive, and nonmetals are electronegative?
Metals are electropositive → they tend to lose electrons and form cations when they combine with non-metals Ex. Na —> Na+ + e- Nonmetals are electronegative → they tend to gain electrons and form anions when they combine with metals Ex. F + e- —> F-
Naming ionic compounds
Monoatomic cations: the name of the main-group monatomic cation is the element name followed by the word "ion" Ex. Na+ → Sodium ion, Mg2+ → Magnesium ion Transition metal monoatomic cations: is the element name followed by the cation charge in roman numerals within parentheses and the word "ion" Ex. Fe2+ → Iron (II) ion, Co3+ → Cobalt (III) ion Monoatomic anion: is the elements name changed to include the suffix "ide" followed by the word "ion" Ex. F- → Fluoride ion, O2- → oxide ion
What is the formal charge of NO3-?
NO3- → 24 e- FC (O1)=6-6-2/2= -1 FC (O2)=6-6-2/2= -1 FC (O3)=6-4-4/2= 0 FC(N)= 5-0-8/2= +1
Which has a greater atomic size between the elements Na, Li, Al
Na is greater than Li, Na is greater than Al. Al<Li<Na
Why is the ionization energy of Na lower than Ne?
Ne has full orbitals and is less likely to give electrons compared to Na.
Know how to calculate nuclear charge and effective nuclear charge.
Nuclear charge is the number of protons Nuclear charge=Z. Effective nuclear charge is Z (number of protons in nucleus) - S (number of core electrons), Z*eff= Z-S. Z*eff is number of valence electrons
Example: Arrange Li, Na, Rb in order to: a) increasing nuclear charge b) increasing effective nuclear charge
Nuclear charge= z Z(Li)= 3, Z(Na)=11, Z(Rb)=37 E*ff= Z-S 3Li= 3-2=1 11Na=11-10=1 37Rb=37-36=1 Z*eff(Li)= Z*eff(Na)= Z*eff(Rb)
Naming covalent compounds
Number of atom of each element in the compound is indicated in the name Omit the prefix for the first element if there is only 1 atom of it Ex: CO2= Carbon dioxide
What is the resonance structure of O3?
O3 :O: = :O - ::O:- → -:O:: - O: = :O:
What is the formal charge of O3?
O3 → 18 e- :O: = :O - :O: - FC= V - N - B/2 FC (Oa)= 6-4-4/2 = 0 FC (Ob)= 6-2-6/2 = +1 FC (Oc)= 6 - 6 - 2/2= -1
Know how to write resonance structures.
Resonance structures are when elements that have a double switch with an element that has an anion (-) in a molecular structure of a molecule. Everything else in the molecule stays the same except the - (anion) moves to be another bond making a double bond and the double bond of the other element moves to be the - (anion).
Naming Simple Hydrocarbons
Stem name refers to number of carbons; ending is always "ane"
What is the covalent compound name for SO2
Sulfur dioxide
What is the name of this acid, H2SO4
Sulfuric acid
Whats the acid name for H2SO4
Sulfuric acid
Which has the greater atomic size between the element Xe, S, Te
Te is greater than S, Te is greater than Xe. S<Xe<Te
Classification of sizes: cations vs. anions vs. non-charged elements.
The size of an ion is related to both the atom itself & the ion charge. Cations are smaller than the atoms from which they are formed, the non-charged elements. Anions are larger than the atoms from which they are formed, the non-charged elements. Anions are generally larger than cations.
Whats the acid name for HClO3
chloric acid
What is the covalent compound name for N2H4
dinitrous tetrahydride
What is the name of this acid, HCl
hydrochloric acid
What is the name of this acid,HCN
hydrogen cyanide
Whats the acid name for HClO
hypochlorous acid
Core electrons
inner electrons occupying principal quantum numbers that have full s & p orbitals
Define dipole
is a bond or molecules with ends that have opposite charges
Define dipole moment.
it's the measurement of the polarity of a bond. They depend on bond polarity & molecular shape
What is the name of this acid, HNO2
nitrous acid
Whats the acid name for HNO2
nitrous acid
Whats the covalent compound name for PCl5
phosphorous pentachloride
Whats the covalent compound name for SO2
sulfur dioxide
Electron affinity
this is the energy change when a gaseous atom gains an electron
