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Unit 3 Question Packet
Atoms, Ions, & Isotopes
Name …………………KEY………………………
Period ………….
SKILLS
1. interpreting MODELS OF THE ATOM
2. determining # of SUBATOMIC PARTICLES
IN ATOMS
3. identifying GROUND-STATE & EXCITED-STATE
ELECTRON CONFIGURATIONS
SKILL #1:
1.
interpreting MODELS OF THE ATOM
4. interpreting ISOTOPIC NOTATION
5. CALCULATING ATOMIC MASS
6. determining # of SUBATOMIC PARTICLES
IN IONS
- refer to your notes and RB p. 33-34
One model of the atom states that atoms are tiny particles composed of a uniform mixture
of positive and negative charges. Scientists conducted an experiment where alpha particles
were aimed at a thin layer of gold atoms.
Most of the alpha particles passed directly through the gold atoms. A few alpha particles
were deflected from their straight-line paths. An illustration of the experiment is shown below.
a. Most of the alpha particles passed directly through
the gold atoms undisturbed. What does this
evidence suggest about the structure of the gold
atoms?
Mostly empty space
b. A few of the alpha particles were deflected. What
does this evidence suggest about the structure of
the gold atoms?
Small, dense, positively-charged center (nucleus)
c. How should the original model be revised based on the results of this experiment?
The atom has a positively charged nucleus; negative electrons surround the outside.
The positive charges are in the nucleus; electrons are not mixed in the nucleus.
nucleus smaller than atom
2.
In 1897, J. J. Thomson demonstrated in an experiment that cathode rays were deflected by an
electric field. This suggested that cathode rays were composed of negatively charged particles
found in all atoms. Thomson concluded that the atom was a positively charged sphere of almost
uniform density in which negatively charged particles were embedded. The total negative charge in
the atom was balanced by the positive charge, making the atom electrically neutral.
In the early 1900s, Ernest Rutherford bombarded a very thin sheet of gold foil with alpha particles.
After interpreting the results of the gold foil experiment, Rutherford proposed a more sophisticated
model of the atom.
a. State one conclusion from Rutherford’s experiment that contradicts one conclusion made by
Thomson.
An atom has a nucleus that is positively charged; An atom is mostly empty space.
Negatively charged particles are located outside the positive nucleus.
b. State one aspect of the modern model of the atom that agrees with a conclusion made by
Thomson.
An atom has equal amounts of negative and positive charge.
An atom has an equal number of protons and electrons.
All atoms contain electrons.
Electrons are negatively charged.
SKILL #2:
determining # of SUBATOMIC PARTICLES
- refer to your notes, RB p. 35-37, Table S,
and the Periodic Table
3. Complete the table below based on information provided for each atom.
Remember: all atoms are electrically neutral.
Atom
A
B
C
D
E
F
G
Protons Electrons Neutrons Mass Atomic Nuclear
# of
Nuclear Element’s
#
#
charge Nucleons diagram Symbol
58 n
44
44
58
102
44
+44
102
Ru
44 p
125 n
84
84
125
209
84
+84
209
Po
84 p
31 n
25
25
31
56
25
+25
56
Mn
25 p
140 n
89
89
140
229
89
+89
229
Ac
89 p
30 n
28
28
30
58
28
+28
58
Ni
28 p
141 n
92
92
141
233
92
+92
233
U
92 p
82 n
56
56
82
138
56
+56
138
Ba
56 p
SKILL #3:
Identifying GROUND-STATE & EXCITED-STATE
ELECTRON CONFIGURATIONS
- refer to your notes, RB p. 40-42,
and the Periodic Table
4. Complete the table below. The first one is done for you.
Electron
Total # Total # of e- shell with
configuration
of
e- shells
the highest
e-‘s
energy e-‘s
Atom A 2-8-4
14
3
3rd
Atom B 2-3-1
6
3
3rd
Atom C 2-8-7-1
18
4
4th
Atom D 2-8-18-6
34
4
4th
Atom E 2-8-18-17-5
50
5
5th
Atom F 1-7
8
2
2nd
Excited- or
ground-state
Atom’s
symbol
ground
excited
excited
ground
excited
excited
Si
C
Ar
Se
Sn
O
5. An atom has an atomic number of 9, a mass number of 19, and an electron
configuration of 2–6–1.
a. What is the total number of neutrons in this atom? 10
b. Explain why the number of electrons in the second and third shells shows that this
atom is in an excited state.
The third shell has one electron before the second shell is completely filled.
Do not allow credit for a response that simply restates that the electron configuration is 2-6-1.
6. Complete the table below. The first one is done for you. Use Table S and the P.T.
Ground-state
Element
Element
# of valence
An excited-state
electron
symbol
name
electrons
electron configuration
configuration
O
oxygen
2-6
6
2-5-1
Mg
magnesium
2-8-2
2
2-8-1-1
He
helium
2
2
1-1
K
potassium
2-8-8-1
1
2-8-7-2
N
nitrogen
2-5
5
2-4-1
P
phosphorus
2-8-5
5
2-8-4-1
F
fluorine
2-7
7
2-6-1
Sr
strontium
2-8-18-8-2
2
2-8-18-8-1-1
Al
aluminum
2-8-3
3
2-8-2-1
Br
bromine
2-8-18-7
7
2-8-17-8
Cu
copper
2-8-18-1
1
2-8-17-2
7. Electron transitions from one shell to another are given for four different atoms below:
a.
b.
c.
d.
e.
f.
SKILL #4:
Atom G:
3rd shell to 2nd shell
Atom I:
4th shell to 6th shell
Atom H:
1st shell to 4th shell
Atom J:
5th shell to 3rd shell
In which atom(s) is energy absorbed during the e- transition?
H, I
In which atom(s) is energy released during the e- transition?
G, J
In which atom(s) would spectral lines be observed? G,J
In which atom is the greatest amount of energy absorbed?
H (jumps 3 shells)
In which atom is the greatest amount of energy released?
J (falls 2 shells)
In atom G, compare the energy of the electron in the 3rd shell to that of the electron
in the 2nd shell. The e- in the 3rd shell has higher energy than the e- in the 2nd shell.
Interpreting ISOTOPIC NOTATION
– refer to your notes and RB p. 38
8. Copper has two naturally-occuring isotopes, Cu-63 and Cu-65. State, in terms of
subatomic particles, how an atom of Cu-63 differs from an atom of Cu-65.
An atom of copper-63 has two fewer neutrons than an atom of copper-65. Or…
An atom of Cu-63 has 34 neutrons and an atom of Cu-65 has 36 neutrons.
9. Complete the table below. Use the P.T.
Protons Electrons Neutrons Mass Atomic Nuclear Isotope
Atom
#
#
charge symbol
SKILL #5:
A
50
50
69
119
50
+50
B
8
8
11
19
8
+8
C
9
9
10
19
9
+9
D
19
19
20
39
19
+19
E
17
17
22
39
17
+17
F
50
50
71
121
50
+50
a. Which two atoms in the table above represent isotopes of the same element?
A and F
CALCULATING ATOMIC MASS
– refer to your notes and RB p. 39
10. Calculate the atomic mass for each element below, given the relative abundances and
the mass numbers of the isotopes. Show ALL work. (GSSC)
a. 19.78% of B-10
80.22% of B-11
G
S:
S:
C:
b. 78.70% of Mg-24
10.13% of Mg-25
11.17% of Mg-26
G
S:
S:
C:
c. 93.12% of K-39
6.88% of K-41
G
S:
S:
decimal x mass = products (add)
0.1978 x 10 = 1.978
0.8022 x 11 = 8.8242
10.80 amu
10.80 is between 10 and 11, closer to 11 (80%)
decimal x mass = products (add)
0.7870 x 24 = 18.888
0.1013 x 25 = 2.5325
0.1117 x 26 = 2.9042
24.32 amu
24.32 is between 24 and 26, closer to 24 (79%)
decimal x mass = products (add)
0.9312 x 39 = 36.3168
0.0688 x 41 = 2.8208
39.1 amu
C:
39.1 is between 39 and 41, closer to 39 (93%)
11. Base your answers to the following questions on the data table below, which shows three
isotopes of neon.
a. In terms of atomic particles, state one difference between these three isotopes of
neon.
different number of neutrons
b. Based on the atomic masses and the natural abundances shown in the data table,
show a correct numerical setup for calculating the average atomic mass of neon.
S:
decimal x mass = products (add)
S:
0.909 x 19.99 = 18.17091
0.003 x 20.99 = 0.06297
0.088 x 21.99 = 1.93512
20.17 amu
C: 20.17 is between 19.99 and 21.99, closer to 19.99 (91%)
c. Based on natural abundances, the average atomic mass of neon is closest to which
whole number? 20
12. Naturally occurring elemental carbon is a mixture of isotopes. The percent composition
of the two most abundant isotopes is listed below.
• 98.93% of the carbon atoms have a mass of 12.00 atomic mass units.
• 1.07% of the carbon atoms have a mass of 13.00 atomic mass units.
a. Show a correct numerical setup for calculating the average atomic mass of carbon.
S:
decimal x mass = products (add)
S:
0.9893 x 12.00 = 11.8716
0.0107 x 13.00 = 0.1391
12.01 amu
C: 12.01 is beween 12 and 13, closer to 12 (99%)
b. Describe, in terms of subatomic particles found in the nucleus, one difference
between the nuclei of carbon-12 atoms and the nuclei of carbon-13 atoms. The
response must include both isotopes.
Carbon-13 has one more neutron than carbon-12.
13. The atomic mass of element A is 63.6 atomic mass units. The only naturally occurring
isotopes of element A are A-63 and A-65. The percent abundances in a naturally
occurring sample of element A are closest to
(1) 31% A-63 and 69% A-65
(3) 69% A-63 and 31% A-65
(2) 50% A-63 and 50% A-65
(4) 100% A-63 and 0% A-65
14. A 100.00-gram sample of naturally occurring boron contains 19.78 grams of boron-10
(atomic mass = 10.01 atomic mass units) and 80.22 grams of boron-11 (atomic mass =
11.01 atomic mass units). Which numerical setup can be used to determine the atomic
mass of naturally occurring boron? 1
SKILL #6:
Determining # of SUBATOMIC PARTICLES
IN IONS
– refer to your notes, RB p. 44-45, & P.T.
15. Complete the table below.
2-8
E.C.
same
as…
Ne
Ion larger or
smaller than
atom?
smaller
18
2-8-8
Ar
larger
38
36
2-8-18-8
Kr
smaller
+1
11
10
2-8
Ne
smaller
Mg2+
+2
12
10
2-8
Ne
smaller
H+
+1
1
0
0
a proton
smaller
O2-
-2
8
10
2-8
Ne
larger
Cl-
-1
17
18
2-8-8
Ar
larger
K+
+1
19
18
2-8-8
Ar
smaller
F-
-1
9
10
2-8
Ne
larger
Ion
Charge
# of
protons
# of
electrons
Electron
configuration
Al3+
+3
13
10
P3-
-3
15
Sr2+
+2
Na+
16. Explain, in terms of subatomic particles, why an oxygen atom is electrically neutral.
An atom of oxygen has 8 protons and 8 electrons.
17. Explain, in terms of subatomic particles, why an oxide ion, O2-, has a negative charge.
An oxide ion has 2 more electrons than protons, giving it a charge of -2.
18. Compare the number of protons to the number of electrons in a positive ion.
A positive ion has more protons than electrons
19. Compare the number of protons to the number of electrons in a negative ion.
A negative ion has more electrons than protons
20. Explain, in terms of subatomic particles, why a chlorine ion is larger than a chlorine atom.
A chlorine ion has one more electron than a chlorine atom.