Answer Key: Review:
Periodicity and Bonding
Go to the Review Sheet.
- Noble gases - last family on the periodic table;
representative elements - s and p blocks; alkali metals -
first family; alkaline earth metals - second family;
halogens - family second from the end; transition metals
- d-block elements; inner transition elements - f-block
- See your text for the full explanation here. Be able to
explain the trends. When time permits, I will write it
- Cl-1. It has gained an electron and still has
the same number of energy levels and protons, so the size
is larger to allow space for the electron.
- Sr+2, Rb+1, Kr, Br-1, Se-2,
As-3. They all have the same number of
electrons, thus the same number of energy levels, but the
protons differ. Sr has the most protons so it will pull
the electrons in tighter than the others. The size
increases as the number of protons decrease.
- As you go across the 3rd period the ionic sizes decreases
until silicon. The ions of sodium through silicon all
have the same number of electrons but silicon has more
protons, which pulls the electrons in tighter. At
phosphorus the ionic size increases dramatically, then
decreases to chlorine. Phosphorus gains 3 e-
and has fewer protons than sulfur which only gains 2 e-
and chlorine which only gains 1 e-. Melting
point increases as you go across, peaks at Si, then
decreases to Ar.
- 2 Na + 2 H2O
--> 2 NaOH + H2
- Cl2 + 2 Br-1
--> 2 Cl-1 +
- I2 + Cl-1
--> no reaction
- Br2 + H2O
--> HBr + HOBr
- 2 K + Br2 -->
- Ag+1 Br-1
- As you go down the family the reactivity increases.
Alkali metals want to lose electrons and as you go down a
column the size increases making it easier for an
electron to be removed, so therefore the reactivity
- As you go down the halogen family the reactivity
decreases. Halogens want to gain electrons and the
smaller size at the top of the family allows electrons to
be gained easier than the larger sizes.
- a) 7 b) 4 c) 1 d) 6 e) 8
- a) gain 1 b) gain 1 c) lose 2 d)
- To obtain a full outer shell and become like an inert
- a) MgBr2 b) Al2S3
- a) magnesium bromide b) aluminum sulfide c) lithium
- Ionic - complete transfer of electrons, covalent -
sharing of electrons
- Polar - net partial charge, difference in
electronegativity between the two elements. Nonpolar -
very small difference in electronegativity, no partial
charges. Both are covalent bonds.
- a) tetrahedral b) pyramidal c) bent
d) tetrahedral e) linear f) (square planar)
g) trigonal bipyramidal h) trigonal planar
i) linear j) octahedron
- a,b,e,i - polar the rest - nonpolar
- double - shorter bond length, more electrons shared
- Valence Shell Electron Pair Repulsion theory - all atoms
(shared pairs) and unshared electrons want to spread out
as much as possible.
- (O - F, Cl - O), Li - N, K - O
- a) ionic b) covalent c) ionic d)
ionic e) covalent
- It is ionic between the Na+ and the PO4-3
ions. Covalent within the PO4-3
- Stronger dipole interactions which occur between
molecules when H is bonded to either F, N, or O. This
occurs because H is very electron deficient, having more
of a partial positive charge than usual. The others have
more of a partial negative charge.
- HCl is a dipole and the d+
on the H is attracted to Cl (with a d-)
on a separate molecule. This attraction holds the
molecules closer together to allow the substance to
become a liquid.
- Dispersion forces or Induced dipoles. Dispersion forces
are thought to be do to the motion of electrons. The more
electrons present, the stronger the dispersion forces.
Induced dipoles may also play a factor. An instantaneous
dipole may form on one I2 molecule which can
induce a dipole in another and have an instantaneous,
- It is ionic and the + and - ions are attracted to the d+ and d- on the water molecule.
- Yes. It is polar and will have dipole interactions with
water to allow it to dissolve.
- No. It is nonpolar and will not be attracted to water.
(Small amounts of nonpolar substances may dissolve due to
induced dipoles, but not much.)
- For 24, use oil or another nonpolar liquid.
- The polar bonds pull evenly on the central atom, giving
no net result.
- network solid
- CH4 has the largest bond angles because all
the electron pairs are shared. NH3 is smaller
because the unshared pair of electrons repel the shared
pairs (hydrogen atoms) more than a shared pair, pushing
the hydrogens closer together. H2O has the
smallest bond angle because it has two unshared pairs of
electrons which repel each other even more, pushing the
hydrogens even closer together.
- C2H2, C2H4, C2H6.
Triple bonds are the shortest, single bonds the longest.
- Forming 3 C-Cl bonds, 1 C-H bond. Enthalpy = 3(339) +
1(413) = 1430 kJ.
- CH4 (g) + 2 Cl2 (g)
+ 2 F2 (g) -->
CF2Cl2 (g) + 2 HF
(g) + 2 HCl (g)
DHrxn = Energy
needed to break bonds - Energy needed to form bonds.
Bonds to break: 4(C-H), 2(Cl-Cl), 2(F-F)
Bonds to form: 2(C-F), 2(C-Cl), 2(H-F), 2(H-Cl)
DHrxn = [4(413) +
2(239) + 2(154)] - [2(485) + 2(339) + 2(565) + 2(427)] =
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