Download January Exam Review

January Exam Review
A- Simplified atomic model
P+ and n° in the nucleus. é on orbits with a 2-8-8-2 possibility.
1. Which of the following best represents the simplified atomic model of a potassium atom,
A)
39
K?
19
C)
19 p +
20 n°
19 p +
39 n°
2e 8e 8e 1e
2e 8e 8e 1e
B)
D)
19 p +
39 n°
19 p +
20 n°
2e 8e 9e
2e 8e 9e
B- Periodic trends
Properties followed from one period to the next.
Atomic radius (size) increases from ←↓
Reactivity in metals increases ←↓
Reactivity in non-metals increases →↑
Ionization and electro negativity increases from →↑
1. The graph below shows the electronegativity index of some elements of the periodic table.
4,5
4
3,5
3
2,5
2
1,5
1
0,5
0
H
He
Li
Be
B
C
N
O
F
Ne
Na Mg
Al
Si
P
S
Cl
Ar
K
Ca
Ga
Ge
As
Se
Which of the following statement is true?
A) The electronegativity index steadily increases within the same family.
B) The electronegativity index steadily increases, then drops to 0 within the same period.
Br
Kr
C) The electronegativity index remains constant within the same family period as one goes from
left to right on the periodic table.
D) The electronegativity index steadily decreases within the same period.
2. Based on the graphs below, in general terms what happens to the atomic radius and ionization
energy as the atomic number increases across a given period?
Atomic Radius vs. Atomic Number
300
Atomic
Radius
(pm)
250
200
150
100
50
0
1
11
21
31
41
51
61
71
81
91
101
Atomic Number
Ionization Energy vs. Atomic Number
Ionization
energy
(kJ/mol)
2500
2000
1500
1000
500
0
1
11
21
31
41
51
61
71
81
91
101
Atomic Number
A) As the atomic number increases, both the atomic radius and ionization energy generally
increase.
B) As the atomic number increases, both the atomic radius and ionization energy generally
decrease.
C) CAs the atomic number increases, the atomic radius generally increases and the ionization
)energy generally decreases.
As the atomic number increases, the atomic radius generally decreases and the ionization
D) D
)energy generally increases.
3. The graph below illustrates the atomic radius of certain elements as a function of their atomic
numbers.
Atomic radius
-9
(10 cm)
0.25
0.20
0.15
0.10
Ar
Ne
0.05
He
0
5
10
15
20
25
30
Atomic number
According to this graph, which statement best describes the change in the atomic radius as you move
across a period?
A) The size of the atomic radius increases as you move from left to right across a period.
B) The size of the atomic radius decreases then increases across a period.
C) The size of the atomic radius decreases as you move from left to right across a period.
D) The size of the atomic radius increases and then decreases across a period.
4. The atomic size of an element is an example of a periodic property. The atomic size of the four
elements below can be illustrated by using the atomic radius of each of these elements.
Atom of element 1
Atom of element 2
r1
r 1 : 0.205 nm
Atom of element 3
r2
Atom of element 4
r3
r2 : 0.140 nm
r4
r 3 : 0.117 nm
r4 : 0.091 nm
In which of the following periodic tables are these elements correctly placed?
A)
H
C)
1
H
1
2
3
4
3
2
1
2
3
4
B)
4
D)
3
H
4
2
1
5. The following graph shows the ionization energies of certain elements as a function of their
atomic numbers.
Ionization
Energy
(eV)
25.00
20.00
15.00
10.00
5.00
0
5
10
15
20
25
30
35
40
Atomic Number
According to this graph, which of the following statements is TRUE?
A) Within a period, the ionization energy usually increases as the atomic number increases.
B) Within a period, the ionization energy usually decreases as the atomic number increases.
C) In general, the ionization energy of the elements in Period 3 is greater than the ionization
energy of the elements in Period 2.
D) The ionization energy of the elements in Period 4 varies regularly when the atomic number
increases regularly.
6. The following graph shows the atomic radius of certain elements as a function of their atomic
number.
Atomic Radius
(10 -9
cm)
0.25
0.20
0.15
0.10
Ar
Ne
0.05
He
0
5
10
15
20
25
30
Atomic Number
According to the graph, which of the following is the best description of the variation in atomic radius
across a period?
A) The atomic radius increases from left to right.
B) The atomic radius decreases and then increases across a period.
C) The atomic radius decreases from left to right.
D) The atomic radius increases and then decreases across a period.
7. The graph below illustrates the atomic radius of certain elements as a function of their atomic
numbers.
The following graphs illustrate various trends of the atoms on the periodic table.
I
II
III
Which graphs represent the trend for ionization energy and for atomic radius?
A)
Ionization energy
Atomic radius -
II
I
B)
Ionization energy
Atomic radius -
II
III
C)
Ionization energy
Atomic radius -
III
II
D)
Ionization energy
Atomic radius -
III
I
C- Isotopes
An element with different number of neutrons, but the same number of protons (mass number
will change)
3 → mass number
H1
H2
H3
proton number H
1. In general, in the periodic table, the atomic masses of elements increase as their atomic
numbers increase. There are, however, exceptions to this rule. Which of the following accounts
for these exceptions?
A) The number of electrons increases irregularly.
B) The number of particles in the nucleus increases regularly.
C) The number of neutrons increases irregularly.
D) The number of protons increases regularly.
2. Silicon comes as three different isotopes: Si 27, Si 28 and S1 29
a- For each form of silicon give the atomic number
b- For each form of silicon give the neutron number
c- Which form of Silicon is most abundant
D- Radioactivity
Three types of radioactive rays exist. The weakest is alpha which is stopped by paper and has a
positive charge, beta is stopped by foil paper and is negatively charged and Gamma had no
charge and is stopped by concrete.
1. The results of an experiment dealing with radioactivity are illustrated below.
Negative Plate
Fluorescent Screen
_
α
γ
β
Radioactive Source
+
Positive Plate
What can you conclude from this experiment?
A) The atom consists of a nucleus and electrons.
B) The alpha and beta radiation is electrically charged.
C) The alpha and beta particles and the gamma rays have different masses.
D) The alpha, beta and gamma radiation is able to penetrate matter.
2. A radioactive source emits both beta, β, and gamma,, radiation.
The radiation is focused into a beam and fired between two charged plates as shown in the diagram
below.
Positive plate
Phosphorescent
screen
Radiation
source
Negative plate
What results would be expected?
A)  and  radiation would pass straight through the plates with no deflection.
B)  and  radiation would be deflected towards the negative plate.
C) Some radiation would be deflected towards the negative plate and some would pass straight
through the plates.
D) Some radiation would be deflected towards the positive plate and some would pass straight
through the plates.
3. The illustration at the right shows radiation
from a radioactive point source passing
through an electric field.
Which of the following correctly describes the rays formed after the radiation has passed through the
electric field?
A) Ray 1 : negatively charged gamma () rays
Ray 2 : neutral alpha () particles
Ray 3 : positively charged beta () particles
B) Ray 1 : negatively charged beta () particles
Ray 2 : neutral gamma () rays
Ray 3 : positively charged alpha () particles
C) Ray 1 : positively charged beta () particles
Ray 2 : neutral gamma () ray
Ray 3 : negatively charged alpha () particles
D) Ray 1 : negatively charged alpha () particles
Ray 2 : neutral beta () particles
Ray 3 : positively charged gamma () rays
4. The diagram below illustrates three types of radiation directed between two electrically charged
plates toward a screen.
+
β
γ
α
_
What can be concluded from the results?
A) Only alpha radiation has an electric charge.
B) Only beta radiation has an electric charge.
C) Both alpha and beta radiation have electric charges.
D) Alpha, beta, and gamma radiation have electric charges.
E- Nucleus stability
The larger the nucleus more unstable it is because harder to make protons stop repelling
themselves. All above 83 unstable
F- Half life
The time it takes a radioactive material to decay.
1. 15 g of uranium takes 35 000 years. Fill in the table to determine the percentage and amount
left after 5 half lives have passed.
Gram
Decay time
Percent
2. If you are using radioactive substances in your body for medical reasons. Would you want to use
an isotope with a long or short half life? Why
3. If you are using radioactive substances to date an old bone. Would you want to use an iaotope
with a short or long half life? Why
G- Nuclear fusion and fission
Definition
Nuclear fusion
2 small nuclei collide and form
a heavier nucleus
Nuclear fission
Nucleus of the atom splits
apart into lighter atoms
Fission
1
0n
Fusion
H2
+
235
92u
+
→
55Cs
140
H2 →
+
93
37Rb
He3 +
+ 20n1
1
0n
H- Bonds
Ionic: metal donate electrons and non-metal accept electrons. Ions are formed.
Crossover rule- Write element symbols, give their valence, crossover the valence.
1. Crossover rule for molecular formula
Beryllium sulfide
Sodium oxide
Lewis diagram
Molecular formula
Name
Aluminum and
fluorine
Lithium and
phosphorus
Covalent: non-metal s share electrons with non-metals. Ions are not formed.
2. Molecular formula
Diphosphorus trisulfide
Carbon tetrachloride
Lewis diagram
Molecular formula
Name
Phosphorus and
chlorine
Hydrogen and oxygen
Chlorine
Oxygen
Polyatomic ions (radicals)
2 or more nonmetal atoms which act like ionic bonds and become charged
3. Mrs. Turriff and Mrs. Scandar have had enough of Robert the lab tech’s foul mood. They decided
to sneak into the school in the middle of the night and mix all his chemicals. Surprisingly, some
of the mixtures actually formed polyatomic ions while others did not mix since, they were
incompatible. From the list of polyatomic ions below:
Charges:
Nitrate: NO3- Sulphate: SO42- Phosphate: PO43Hydroxide: OHCa(NO3)2
K(SO4)2
AlPO4
Mg2OH
A- Determine which radicals are possible and which are impossible, justify your answer
B- Rewrite the correct radicals and correct the incorrect ones.
C- Name each radical.
4. Write the chemical formula for the compound formed between the anion PO43- and each of the
following cations :
A) Sodium
B) Calcium
C) Aluminum
5. A compound is composed of hypothetical elements X and Y. X belongs to Family I A(1) and Y
belongs to Family V A(15). What is the molecular formula of this compound?
6. Among the following chemical formulas, which contains two radicals (complex ions)?
A) H2SO4
B) NH4OH
C) NaNO3
D) CaCO3
7. Which group of substances consists only of substances formed by covalent bonds?
A) K2O, PCl3, H2S
C) CH4, CaS, NCl3
B) NaCl, MgO, AlF3
D) NH3, O2, P2O3
8. Which of the following molecular formulas represent ionic bonds?
1.
LiCl
4.
H2O
7.
K2S
2.
O2
5.
AlCl3
8.
N2O3
3.
CH4
6.
CaF2
A) 1, 5, 6 and 7
B) 1, 6, 7 and 8
C) 2, 3, 4 and 5
9. Which of the following compounds have covalent bonds?
1. Na2CO3
5. Ca3N2
2. C3H8
6. P2O5
3. Al4C3
7. PBr5
4. Si3N4
8. Mg3P2
A) 1, 3, 5 and 8
B) 1, 3, 6 and 8
C) 2, 4, 5 and 7
D) 2, 3, 4 and 8
D) 2, 4, 6 and 7
10. of the following statements correctly describe ionic bonds?
1.
In reacting with water, potassium transfers an electron to produce potassium hydroxide, KOH.
2.
In reacting with a metal, sulphur normally accepts two electrons.
3.
Metals often form ionic bonds with one another.
4.
Chlorine atoms share two electrons to form chlorine gas, Cl2.
5.
H2O is an example of an ionic compound.
6.
Copper oxide, CuO, is an example of an ionic compound.
A) 1, 2 and 4
B) 1, 2 and 6
C) 3, 4 and 5
D) 3, 5 and 6
11. Among the following chemical formulas, identify those substances formed as a result of covalent
bonding.
1.
CsF
2.
PBr3
3.
CaI2
4.
BaAt2
5.
SrO
6.
S8
7.
AlCl3
8.
CO2
A) 2, 6 and 8
B) 1, 5 and 7
C) 2, 4 and 8
D) 3, 5 and 7
12. What is the correct molecular formula of a compound formed by an element "Y" from
group IV A (4) and an element "Z" from group VI A (16)? Give the correct molecular formula for
this compound.
13. A compound is made of two hypothetical elements, X and Z. Element X belongs to family II A(2)
and element Z belongs to family V A(15). Which of the formulas below correctly represents this
compound?
A) X2Z3
B) X3Z2
C) X2Z5
D) X5Z2
14. A compound contains the elements X and Y. Element X belongs to Group I A (1). Element Y
belongs to Group VI A (16). What is the molecular formula of this compound?
A) XY2
B) XY6
C) X2Y
D) X6Y
15. Which of the following molecules is not consistent with the octet rule?
A) CF4
B) KO2
C) MgCl2
D) BaO
16. These elements combine to form compounds : Na, Ca, S, N, Al and Br. Which of the chemical
formulas below respect the octet rule?
A) NaBr, Ca2S, Na2S
B) N2S3, SBr, AlS
C) NaBr, Al2S3, NBr3
D) AlS, Na2N, CaS
17. Based on their position in the Periodic Table, which two of the following elements can form
three chemical bonds?
1.
Sodium
2.
Calcium
3.
Aluminum
4.
Chlorine
5.
Phosphorus
6.
Helium
A) 1 and 5
B) 2 and 4
C) 3 and 6
D) 3 and 5
18. Which of the following chemical formulas does not obey the rules of chemical nomenclature?
A) NH3
B) F2O
C) H2O
D) Cl2O
19. Four circular pieces of metal were brought close to one another during a laboratory experiment.
Only one of these pieces of metal is a magnet.
Attraction
Combination
Yes
Piece 1 with piece 2
No

Piece 1 with piece 3

Piece 1 with piece 4

Piece 2 with piece 3

Piece 2 with piece 4

Piece 3 with piece 4
Which piece of metal is a magnet?

20. An electric current flows through a solenoid. Which diagram correctly illustrates the magnetic
field produced by this solenoid?
21. A bar magnet is brought close to a current-bearing solenoid. In which one of the following
situations will there be repulsion?
S
N
S
 +
+ 
S
+ 
N
N
N
S
 +
22. Which of the following diagrams correctly represents the magnetic lines of force between two
solenoids?
A
B
C
D
23. The current intensity is the same in each of the following electromagnets.
Which electromagnet has the strongest magnetic field?
A)
C)
Iron
Glass
B)
D)
Glass
Iron
24. The diagram shows an apparatus that can be used to analyze the factors that affect the
magnetic field of an electromagnet.
Identify 4 of the factors that influence the strength of the magnetic field.
25. What is the electrical force acting on two substances if the charge for each is
4.0 X 10-7 and is placed 2.0 cm apart?
26. What is the electrical force acting on two substances if the charge for each is
5.0 X 10-8 and is placed 1.50 cm apart?