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Chemistry 11A
March 2009
Test #2 – Periodic Table – Review
Answer Key
1. As you go across a row (from left to right) and down a group, explain what happens to each of
the following and why this occurs.
(a) atomic size
(b) ionization energy
a)
Atomic size decreases as you go across a period (from left to right). This is because as
you move electrons are added to the valence shell while protons are being added to the
nucleus. The attraction between this positive nucleus and the increased number of
valence electrons is stronger and therefore the atom is sucked in closer to the nucleus,
making the atom smaller.
Atomic size increases as you go down a group. This is because as you move down,
electrons are being added to the valence shell in a new energy level. Each energy level
is farther from the nucleus and experiences a lesser force of attraction to the nucleus.
This will cause the atom to be larger.
b) Ionization energy increases as you move across a row from left to right. This is
because the electrons are being added to the valence shell while protons are being
added to the nucleus. The attraction between this positive nucleus and the increased
number of valence electrons is stronger and therefore it is harder to remove these
electrons. Also, the shielding effect of the inner electrons across a group decreases
and thus the outer electrons and not being shielded from the positive charge of the
nucleus.
Ionization energy decreases as you go down a group. This is because as you go down a
group a new energy level is introduced which means there are more inner electrons.
These inner electrons will have a large shielding effect on the outer, valence, electrons
which blocks the positive charge of the nucleus. Valence electrons are held less tightly,
due to the lesser attraction, and therefore they are easier to remove.
2. Of each pair choose the element with the larger atomic size:
(a) N or O
(b) Ag or Au
(c) K or Ca
(d) Ge or Ga
3. Of each pair choose the element with the larger ionization energy:
(a) N or O
(b) Ag or Au
(c) K or Ca
(d) Ge or Ga
4. Give the name and symbol for the element found in:
(a) alkaline earth metals group, period 4
Calcium, Ca
(c) alkali metals, period 4
Potassium, K
(e) oxygen group, period 6
Polonium, Po
(b) noble gases, period 2
Neon, Ne
(d) halogens, period 3
Chlorine, Cl
(f) carbon group, period 5
Tin, Sn
Chemistry 11A
March 2009
5. State if the following are representative metals, transition metals, nonmetals or metalloids:
(a) Be – representative metal
(b) Cd – transition metal
(c) Mn – transition metal
(d) Cl – nonmetal
(e) Fr – representative metal
(f) Ge – metalloid
6. List the properties of:
(a) Metals
Physical properties of metals include: good conductors of heat and electricity, luster,
malleable, ductile, high densities, high boiling points, high melting points, they resist
stretching and twisting, and are solids at room temperature
(b) Nonmetals
Physical properties of nonmetals include: no luster, poor conductors, low densities, low
melting points, low boiling points, and they may be solid, liquid, or gas at room temperature.
(c) Metalloids or semimetals
Metalloids have properties of both metals and nonmetals; they are usually semi-conductors
of electricity
7. Who is Dmitri Mendeleev, and what was his contribution to chemistry?
Dmitri Mendeleev was a Russian scientist credited with creating the first periodic table. He
arranged all of the known elements in order of increasing atomic mass. He placed the elements
in rows and columns so that elements with similar properties would be located together. He
left blank spaces in his periodic table where no known elements seemed to fit. He explained
that these blank spaces represented elements that had not yet been discovered, and based on
their position in the periodic table, Mendeleev was able to predict the properties of these
undiscovered elements. When these elements were discovered, their properties were very
similar to those predicted by Mendeleev.
8. How is the modern periodic table different from the first periodic table?
The modern periodic table contains more elements than the one created by Mendeleev because
more elements have been discovered, this is not a significant difference however. The main
difference between Mendeleev's periodic table and the modern periodic table is that
Mendeleev's was arranged in order of increasing atomic mass and the modern periodic table is
arranged in order of increasing atomic number. This corrects the few inconsistencies found in
Mendeleev's table.
9. See periodic table on the wall.
10. Use electron dot symbols (Lewis structure) to determine the formula unit and then name the
ionic compounds formed when the following elements combine.
a) potassium and chlorine
Chemistry 11A
b) calcium and chlorine
March 2009
c) aluminum and oxygen
d) beryllium and phosphorus
11. Write the electron dot structures for each of the following elements.
a. Na
b. Be
c. Ge
d. Be
e. F
12. What are cations and anions? How and why are cations and anions produced?
Cations are positively charged ions while anions are negatively charged ions. Cations are
produced when an atom gives away its valence electrons making it have more of a positivite
charge. Anions are produced when an atom accepts electrons making have more of a negative
charge.
13. Write the correct chemical formula for the compound formed by the following pairs of ions:
a. Na+ and FNaF
b. K+ and S2K2S
2+
33+
2c. Ca and N
Ca3N2
d. Al and O
Al2O3
14. Which of the following pairs of elements are most likely to form ionic compounds?
a. chlorine and bromine
b. potassium and helium
c. lithium and fluorine
d. iodine and sodium
15. Write the formula for the ions in the following compounds.
a. LiF
Li+ and Fb. BaO
Ba2+ and O23+
2d. Ga2S3
Ga and S
e. Ca3N2
Ca2+ and N3-
c. Na2S
Na+ and S2-
16. Draw the electron dot structure for the following covalent molecules:
a) H2S
b) PH3
c) BrF
17. What is a coordinate covalent bond? Provide an example.
A coordinate covalent bond is when an atom donates two electrons to the shared pair of
electrons. An example is in the compound NH4+
18. What is a resonance structure? Provide an example.
19. Name or write the formula for the given compounds.
a) MgS
r) magnesium oxide
b) KBr
s) potassium phosphate
Chemistry 11A
c) As4O10
March 2009
t) calcium nitride
d) Al2O3
u) tin(IV) sulfate
e) NH4NO3
v) potassium iodide
f) SrF2
w) phosphoric acid
g) BrO3
x) sodium sulfide
h) Ni(CH3COO)2
y) tin(II) carbonate
i) PbBr4
z) hydrobromic acid
j) H2CO3(aq)
aa) lead(IV) iodide
k) Li2S
bb) boron trifluoride
l) BN
cc) chlorine monoxide
m) Ba3N2
dd) oxygen difluoride
n) H2SO3(aq)
ee) dinitrogen monoxide
o) H3PO3(aq)
ff) hydrochloric acid
p) Pb3N2
gg) copper(I) sulfide
q) HNO3(aq)
hh) nitrous acid