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Atomic Structure & Electron Arrangement Test Review
Practice Questions:
1. The atomic number is equal to the number of protons.
2. The mass number is equal to the protons+ neutrons.
3. Electrons in the outermost energy level are known as valence electrons and are available to be lost,
gained or shared when molecules are formed.
4. What causes an atom to be neutrally charged?
An equal number of protons and electrons
5. Describe how an atom would become negatively charged.
To be negatively charged, an atom must have gained more electrons.
Identify the major contribution of each of the following to current atomic theory (be sure
to include any model that they proposed and the experiment that they did):
6. Aristotle – everything was made from earth, wind, fire, water, and ether; alchemist
7. Democritus – first to propose the idea of an atom (indivisible particle)!
8. Dalton – developed the basis for the modern atomic theory
9. Thomson - used the cathode ray tube to discover the first subatomic particle the electron; developed the Plum Pudding Model
10. Rutherford - Gold foil experiment- expected all of the radiation to pass
through and was very surprised when some of the particles were deflected led to the discovery of the NUCLEUS (centrally located positive charge) and the concept that the
atom is mostly empty space. Also discovered the proton and neutron.
11. Bohr - His atomic model (planetary model) had atoms built up of successive
orbital shells of electrons. Electrons move between shells based on specific
amounts of energy being lost or gained.
12. Electron Cloud Model - This model is based on quantum mechanics which
states that you cannot know the speed and location of a particle. So this
model shows the most probable location of the electrons.
13. List the four/five points of Dalton’s Atomic Theory and indicate which ones are known to be
incorrect today.
• All matter is composed of tiny particles called atoms. TRUE
• Atoms of an element are identical in size, mass and other properties. FALSE (isotopes)
• Atoms cannot be created, destroyed or subdivided. FALSE (subatomic particles)
• Atoms of different elements can combine in simple whole number ratios to form
compounds. TRUE
• In chemical reactions, atoms are combined, separated or rearranged. TRUE
Compare the subatomic particles according to the following criteria: LOCATION IN THE
ATOM, CHARGE AND MASS.
14. Proton – in the nucleus, positive charge, mass = 1 amu
15. Neutron - in the nucleus, neutral, mass = 1 amu
16. Electron – in the electron cloud around the nucleus, negative charge, mass = 0 amu
Complete the following chart:
Isotope Name
Carbon-13
Nitrogen - 17
Boron - 11
Francium - 223
Nuclear
Atomic
Mass
# of
# of
# of
Symbol
Number
Number
Protons
Neutrons
Electrons
C
6
13
6
7
6
N
7
17
7
10
7
B
5
11
5
6
5
Fr
87
223
87
136
87
13
6
17
7
11
223
5
87
17. There are three common isotopes of hydrogen: protium – 1H, deuterium – 2H, and tritium – 3H.
Based on the average atomic mass given on the periodic table, predict which isotope is most
common and explain your answer.
Since the average atomic mass is closest to 1 amu, protium must be the most common
because the weighted average will be closest to the most abundant isotope.
18. An element consists of three naturally occurring isotopes with the following mass numbers: 24, 25
and 26. The relative abundances of these three isotopes are 78.70, 10.13 and 11.17 percent
respectively. Calculate the average atomic mass and identify the element. Show your work!
(24 x .7870) + (25 x .1013) + (26 x .1117) = 24.3247 amu - Magnesium
Use this graph of mass spec data to answer questions #17 – 20.
19. What masses of isotopes are observed?
35 amu and 37 amu
20. What percentage of each isotope is observed?
35
Cl – 75% 37Cl – 25%
21. What is the average atomic mass of the element? SHOW ALL WORK!
(35 x .75) + (37 x .25) = 35.5 amu
22. Atoms of what element is presented in the graph?
Chlorine
23. Write T for true or F for false. If a statement is false, replace the underlined word with one that will
make the statement true, and write your correction in the blank provided.
a. If two electrons occupy the same orbital, they must have opposite spins. TRUE
b. Electrons occupy the highest energy level possible. FALSE - lowest
c. Single electrons in an orbital of equal energy spin in opposite directions. FALSE – the same
24. Complete the following table
Energy level Number of
Name of
Number of Max number
sublevels
sublevels
orbitals
Of electron
1
1
s
1
2
2
2
s,p
4
8
3
3
s,p,d
9
18
4
4
s,p,d,f
16
32
25. Answer the following short answer questions
a. What is the shape of an “s” orbital?
Sphere
b. What is the shape of a “p” orbital?
dumbbell
26. Draw orbital diagrams for
a. Beryllium
b. Carbon
c. Aluminum
27. Write electron configurations (full and Noble gas) for
a. Lithium
a. 1s22s1
b. [He] 2s1
b. Arsenic
a. 1s22s22p63s23p64s23d104p3
b. [Ar] 4s23d104p3
c. Silver
a. 1s22s22p63s23p64s23d104p65s24d9
b. [Kr] 5s24d9
d. Uranium
a. 1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s25f4
b. [Rn] 7s25f4
28. Draw the electron dot diagrams for the following
a. Lithium
b. Arsenic
c. Argon
d. Calcium