Download Chem Unit 2 Review Guide ANSWERS

Name: __________________________
Chemistry- Unit Assessment 2 Review Guide: Periodic Table and Atomic Structure
ANSWERS
1. Complete the following table:
Particle
Location
Proton
In Nucleus
Neutron
In Nucleus
Electron
Outside Nucleus
Relative Charge
Positive
Neutral
Negative
Relative Mass (amu)
1
1
0
2. What is commonly mistaken about the size of the nucleus in most drawings of an atom?
The size of the nucleus is usually represented as far too large. If the atom were the
size of a football stadium, the nucleus would be the size of a peanut at the center of
the field.
3. Complete the following chart on atomic structure:
Element or Atomic #
Mass #
# of
# of
Ion
protons
Neutrons
# of
Electrons
Li
Ba2+
3
56
7
137
3
56
4
81
3
54
F-
9
19
9
10
10
S2Al3+
16
13
32
27
16
13
16
14
18
10
Rn
86
222
86
136
86
Name of
element or
Ion
Lithium
Barium
Ion
Flourine
Ion
Sulfur Ion
Aluminum
Ion
Radon
4. Be familiar with each of the following scientists’ contributions
a. Dalton
Atomic theory
b. Thomson
Plum pudding model – atom has charges scattered throughout
c. Rutherford
Discovered nucleus via gold foil experiment, discovered 3 types of radiation
d. Democritus
First to theorize matter as atoms
e. Bohr
Conceptualized atoms with electrons orbiting the nucleus in fixed locations
f.
Curie
Discovered 2 radioactive elements
g. Mendeleev
Father of the periodic table...predicted properties of undiscovered elements
h. Aristotle
Believed matter was made of 4 fundamental elements
i.
Lavoisier
Law of conservation of mass
5. Classify the following elements as metals (M), metalloids (ML), or nonmetals (NM)
based on their positions on the periodic table.
a. Oxygen NM
e. Europium M
b. Scandium M
f. Cerium M
c. Silicon ML
g. Mercury M
d. Lithium M
6. Draw the nuclear composition (Rutherford Model) of the following isotopes:
Nitrogen-13
Hydrogen-2
Hydrogen-3
Krypton-86
Seven protons
Six neutrons
Seven electrons
One proton
One neutron
One electron
One proton
Two neutrons
One electron
36 protons
50 neutrons
36 electrons
7. What is the major difference between Hydrogen-2 and Hydrogen-3?
Hydrogen-2 and Hydrogen-3 are both isotopes of Hydrogen. They have the same atomic
number (protons), but different masses because Hydrogen-2 has one neutron, while
Hydrogen-3 has two neutrons.
8. Rubidium has two common isotopes, Rb-85 and Rb-87. If the atomic mass of Rubidium
is 85.56 amu, what isotope is more abundant? Explain.
Rb-85 is more abundant. If the amounts were equal, the average would be 86. Since
it is 85.56, there must be more Rb-85 isotopes contributing to the overall atomic
mass.
9. Complete the following table:
K
Group
1A
Period
4
Family Name
Alkali Metals
Two Similar
Elements
Gain/Lost
Electrons
Type of Ion
Ar
8A
3
Noble Gases
Na, Li, Rb, Cs,
Fr
Lose 1
He, Ne, Kr, Rn,
Xe
Lose/Gain 0
Mg
2A
3
Alkaline Earth
Metals
Ca, Sr, Ba, Ra,
Be
Lose 2
1+
0
2+
Cl
7A
3
Halogens
F, Br, I, At
Gain 1
1-
10. Titanium has 5 common isotopes: Ti-46 is 8.0%, Ti-47 is 7.8%, Ti-48 is 73.4%,
Ti-49 is 5.5%, and Ti-50 is 5.3%. What is the average atomic mass of Titanium?
46(.08) + 47(0.780 + 48(.734) + 49(0.55) + 50(.053) = 48.21
11. What is an alpha particle? What is a beta particle?
Alpha particle = helium nucleus (42He) given off by heavy elements (mass >200)
Beta particle = high energy electron (0-1e) given off by smaller elements (mass < 200)
12. Given the starting information for the following nuclear reactions, finish the equation,
using the correct form of radiation. (alpha or beta)
a.
91 Pa----->
b.
4
2H
+ 23089Ac
0
-1e
+
22
11Na
87 Fr----->
4
216
2H +
85At
0
-1e
+ 4020Ca
0
-1e
+ 9944Ru
2H
+ 21884Po
99
43 Tc----->
f.
220
40
19 K----->
e.
22
10 Ne----->
c.
d.
234
220
86 Rn----->
4
13. What is an amu?
Atomic mass unit. Equal to the mass of a proton or neutron.
14.) What is a radioactive isotope?
An unstable atom which decay (break down) and give off radioactive energy.
15.) What makes an atom unstable?
An imbalance in the ratio of protons to neutrons. The farther this ratio gets from
1:1, the more unstable an atom becomes.
16.) Define an element (atom).
The smallest particle of matter that retains the properties of a particular element.
17.) How are chemical reactions different than nuclear reactions? How does the Law of
Conservation of Mass apply to each type of reaction?
Chemical reactions only involve the atoms’ valence electrons. In a nuclear reaction,
the nucleus is actually altered.
The Law of Conservation of Mass holds true during chemical reactions, but is not
during a nuclear reaction, as mass is converted directly to energy and vice versa.
18.) Define what valence electrons are and how to know how many an element from the
representative group has.
Valence electrons are an atom’s outermost electrons. You can tell how many an
atom of an element will have by looking at its group number.
19.) What is an ion? By finding the elements’ location on the periodic table, how can you
determine what kind of ion it will become?
Ions are atoms with a charge due to electron loss/gain. We wrote what charges will
be formed for most groups.
20.) How are anions and cations different?
Anions are negatively charged particles that have gained electrons. Cations are
positively charged particles that have lost electrons.
21.) Solve the following half life problems:
a.- Sodium-24 has a half-life of 15 hours. How much sodium-24 will remain in an 18.0g
sample after 60 hours?
4 half lives (60/15 = 4)…so 1.125g left
b.- After 42 days a 2.0 g sample of phosphorus-32 contains only 0.25g of isotope. What is the
half-life of phosphorus-32?
3 half lives occur to get from 2.0 to 0.25. This happens over 42 days, so 42/3 = 14
days.
22.) Aluminum, silicon and phosphorus are located near each other in the periodic table. Which
of these elements is (a) the largest atom? (b) the atom with the highest ionization energy?
a. Al b. P
23.) (a) Which of the following atoms is smallest in terms of atomic radius: nitrogen, phosphorus,
or arsenic? (b) Which of these atoms has the smallest ionization energy?
a. N
b. As
24.) Define what each of the three major periodic trends is: Electronegativity, First Ionization
Energy, and Atomic Radii.
Electronegativity = “greediness” (affinity) an atom has for another atom’s electrons
1st Ionization Energy = Amount of energy needed to take an electron away from an atom
Atomic Radius = Distance from nucleus to outermost (valence) electrons