Unit 4 Practice Exam
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Period:
Name:
ANSWER KEY
What subatomic particles are found in the nucleus?
protons and neutrons
Give the name and charge for each of the three primary subatomic particles:
a. Electron: -1 charge
b. neutron: no charge
c. proton: +1 charge
How do you find the mass number of a certain isotope? Add the number of protons and
neutrons of the isotope together (most common is the rounded off atomic mass)
What is the difference between mass number and atomic mass? Atomic mass is the weighted
average of all of the masses of all the different isotopes of an atom, while mass number is just
the number of protons and neutrons for a particular isotope
What happens if somehow a proton were added to a nucleus of an atom?
The type of
atom changes to the next atomic number (if no electrons were added it would be a +1 cation).
What happens if somehow a neutron were added to a nucleus of an atom? It’s just a different
isotope of that element, basically same physical properties, just more massive
Where is most of the mass of an atom located?
Inside the nucleus
How much of the atom's volume is found in the nucleus?
Almost none of it
What particle is mostly responsible for an atom's physical properties?
protons
What particle is mostly responsible for an atom's chemical properties?
electrons
What "glues" the nucleus together?
neutrons
What do you call atoms with the same number of protons, but different numbers of neutrons?
isotopes of the atom
What are the most common isotopes of the following?
a. Carbon
Carbon-12
c. Lead Lead-207
b. Zinc
Zinc-65
d. Chlorine Chlorine-35
Write the name of the Uranium isotope with 147 neutrons. Uranium-239 (U has 92 protons,
92 + 147 = mass number = 239, this is not the most common isotope)
Write the number of protons, Neutrons, and electrons, and isotope name for the following
neutral most common isotopes of the following:
a. Zr
p+ = 40, n = 51, e- = 40, zirconium-91
b. Na
p+ = 11, n = 12, e- = 11, sodium-23
c. H
p+ = 1, n = 0, e- = 1, hydrogen-1
+
d. Mg p = 12, n = 12, e- = 12, Magnesium-24
A neutral atom has 19 electrons. What is the atom?
Potassium (because K has 19 protons
to cancel out the 19 electrons)
An atom has 15 protons, 18 electrons, and 16 neutrons. What is the atom, what is its charge,
and what is its mass number?
Phosphorus with a -3 charge and mass number of 31
A lithium atom with a total of 2 electrons is called a what?
+1 lithium cation
What does the row number on the periodic table tell you?
Number of energy levels
occupiedin the ground state
What does the column numbers (on the A groups) of the period table tell you? The number
of electrons in the highest energy level (that are available for bonding) – valence electrons
Draw Bohr diagrams of the following:
a. The most common
b. A +2 Cation of
c. A -2 Anion of
Oxygen atom.
Calcium.
Oxygen.
For the following particles, write what the particle is, it’s charge, relative mass (1 being the
largest, so if one is ½ the size of the largest, you’d say ½ for that particle), & purpose (what
role does it play in the atom).
a. Proton+charged particle in the nucleus of the atom; +1 charge, relative mass of 1, tells what the
atom is, so it’s responsible for the physical characteristics
b. Neutronneutral particle in the nucleus of the atom; 0 charge, relative mass of 1, binds the protons
together
c. Electron- charged particle in space outside the nucleus of the atom; -1 charge, relative mass of
1/2000, responsible for chemical properties and bonding
33.
Excluding the first energy level, the most stable electron configuration has how many
electrons in the valence shell? 8
34.
Which ‘A’ group neutral elements fit in the following categories: highest Energy level (E),
number of valence electrons (V)
a. E1,V2 Helium
c. E3,V3 Aluminum
e. E4,V5 Arsenic
b. E3,V7 Chlorine
d. E5,V6 Tellurium
f. E5,V8 Xenon
35.
Find the highest energy level occupied (E) and number of valence electrons (V) in a neutral
atom of the following:
a. Gallium E4, V3
c. Argon E3, V8
e. Cesium E6, V1
b. Tin E5, V4
d. Phosphorus E3, V5
f. Strontium E5, V2
36.
Why are the atoms in group 18 often called inert?they don’t like to react with anything else
37.
How many electrons will oxygen typically gain when it becomes ionic?2 (has 6, wants 8)
38.
What type of ions do nonmetals form? anions
39.
The group IIA elements will form what ion (include charge)? +2 cations
40.
The group VIA elements will form what type of ion when they are combined with a metal
(include charge)?
-2 anions
41.
What are the most reactive elements (metal and nonmetal) in period 4 of the periodic table and
why? Potassium and Bromine, because Potassium only has one valence electron so it easy to
get rid of it to be like Ar, and Bromine has 7 valence electrons, so it really wants one more to
be like Kr
42.
How do you know if an atom or ion has a stable electron configuration? if the outer shell is
filled with electrons it is stable (8 valence electrons or 2 for helium)
43.
Which group of atoms have a naturally stable electron configuration? Group 18 (8A) – the
noble gasses
44.
What is electronegativity?
22.
45.
How does electronegativity typically change on the periodic table?
a. Why is that?
46.
A metal and a nonmetal will typically have what type of bond?
ionic
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48.
54.
Two nonmetals will typically have what type of bond?
covalent
How can you predict if the bond between two elements will be ionic, polar covalent, or nonpolar covalent?
In ionic bonds, the sum of the charge of the cations and anions needs to be equal to 0 (neutral)
Nitrogen and Magnesium come together to form an ionic substance.
a. The element that forms the cations is
Magnesium . The element that forms the
anions is
Nitrogen
.
b. The symbol for the ionic form of nitrogen is:
N3and magnesium is: Mg2+
c. The formula for the ionic compound will be:
Mg3N2
If a compound is a molecule, you know that there is at least one
in the substance.
Which of the following is not a molecule?
a. SiO2
b. KCl
c. N2
d. C3H8
The formula for ionic compounds can be reduced (Mg2O2 = MgO), but covalently bonded
molecules cannot be reduced (C2H2 is the not the same as CH). Why is that? Ionic compounds
just tell you the ratio of the atoms, since one transfers electrons to the other, they don’t have to
stay near each other, while a covalent molecule tells you the actual number of each type of
atom in the molecule, and because the electrons are shared, the atoms actually must stay beside
each other
Ionic compounds typically have a
melting point because
55.
Are ionic materials typically brittle or malleable?
56.
Ionic materials in solid form can generally be found in a(n)
structure, because
57.
Ionic materials typically conduct electricity when dissolved in water but do not in solid form.
Why is that?
58.
What information does a chemical formula give you? The types and numbers of elements in a
molecule or compound
What is the difference between a single, double, and triple covalent bond?
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d.
61.
Why?
Given the formula of the following ionic compounds write the symbols for each ion.
MgBr2: ions – Mg+2 Br-1 (Magnesium Bromide)
KCl: ions –
K+1 Cl-1 (Potassium Chloride)
Sr3P2: ions –
Sr+2 P-3 (Strontium Phosphide)
Na3N: ions –
Na+1 N-3 (Sodium Nitride)
Given the name of the following compounds write ionic symbols for each ion and the formula:
a. Sodium Nitride: ions – Na+1 N-3
formula –
Na3N
+2 -3
b. Magnesium Phosphide: ions –
Mg P
formula –
Mg3P2
c. Aluminum Sulfide: ions – Al+3 S-2
formula –
Al2S3
d. Aluminum Bromide: ions – Al+3 Br-1
formula –
AlBr3