Download atomic structure studyguide key

Atomic Structure Study Guide-Key
Name:__________________________________
1. a. Identify the main points of John Dalton’s Atomic Theory.
 Atoms are the building blocks of all matter.
 Atoms are indivisible (cannot be divided).
 Atoms of the same element are the same.
 Compounds are composed of two or more atoms that are combined in a fixed ratio.
 Atoms are always conserved during chemical and physical changes.
b.Which of his points was later proven incorrect?
 Atoms are indivisible: Later proven they are composed of subatomic particles.
 Atoms of the same element are the same: Later discovered isotopes of elements and
they are different in the number of neutrons and mass number.
c. Illustrate his model of the atom.
 A circle with no subatomic particles.
2. a. What did J. J. Thomson contribute to the atomic model?
 He was the first to disprove Dalton’s idea that atoms were indivisible by discovering
electrons within atoms. He also proposed there had to be positively charged particles
to balance the electrons because most matter is neutral.
b.Illustrate and explain his Plum Pudding Model of the atom.
 An atom is composed of equal number of protons and electrons equally dispersed
throughout the atom.
3. a. What did Ernest Rutherford contribute to the atomic model?
 He discovered the nucleus and from his data that it was positively charged.
Furthermore from his data, he concluded the atom was primary empty space.
b. What was his experiment called? Gold Foil Experiment
c. Illustrate Rutherford’s model of the atom. Electron moving around the positively charged
nucleus.
d. What was a problem with Rutherford’s model of the atom? The proton’s repulsion force
within the nucleus would cause it to explode. So was not stable based on his model. Also,
he was not sure exactly the electron movement around the nucleus. James Chadwick,
resolved the issue with the nucleus, when he discovered neutrons within the nucleus.
Neutrons minimize the repulsion force between protons by separating them from one
another.
4. a. What did Bohr contribute to the atom?
 He discovered that electrons move in energy levels around the nucleus. From his data,
he concluded that electrons move in fixed, circular paths around the nucleus.
b. Illustrate Bohr’s model of the atom. Electrons moving in circular energy levels
around the nucleus containing protons and neutrons.
5. a. What did Schrodinger contribute to the current atom?
 That electrons move in different shaped paths (not all circular) around the nucleus. He
also determined that electrons can move between energy levels dependent upon the
amount of energy they absorb or release.
b.Illustrate Schrodinger’s current model of the atom?
 Electrons moving in different shaped energy levels around a nucleus containing protons
and neutrons.
6. Which two subatomic particles contribute charge to an atom?
 Protons (p+) and electrons (e-)
7. a. Which two subatomic particles contribute mass to an atom?
 Protons and neutrons
b.Do these subatomic particles contribute mass equally?
Yes, protons and neutrons mass is very similar to one another, so each proton and neutron in an
atom contributes one amu to the atom’s mass.
8. What is an atom’s atomic number? It is the number of protons within an atom. It is located on
the periodic table and it is an atom’s I.D. It is was distinguishes one atom from another.
9. How many protons does gold (Au) have? 79
10. a. What would happen if gold (Au) lost a proton? It would become platinum.
b. What would happened if gold (Au) gained a proton ? It would become mercury.
11. What is an atom’s mass number? Literally the number of protons and neutrons within an
atom’s nucleus. It is an atom’s mass.
12. a. Complete the table below these neutral atoms.
Element
# of protons
# of neutrons
# of electrons
Fe
26
29
26
Zn
30
42
30
Ca
20
22
20
Mn
25
35
25
b. According to the table, rank the elements in decreasing atomic number.
Zn, Fe, Mn, Ca
c. According to the table, rank the elements in increasing mass number.
Ca, Fe, Mn, Zn
d. According to the table, which element has the most number of electrons.
Zn
13. What is an isotope
Atoms of the same element (same number of protons) that different number of neutrons and so
also different mass numbers.
14. Iodine has three isotopes.
I-127 with a natural abundance of 80%.
I-126 with a natural abundance of 17%.
I-128 with a natural abundance of 3 %
a. Complete the table on these neutral isotopes of Iodine.
Iodine Isotopes
# of protons
# of neutrons
# of electrons
I-127
53
74
53
I-126
53
73
53
I-128
53
75
53
a. Why do Iodine’s isotopes have the same atomic number but different mass numbers?
Each isotope of Iodine has different number of neutrons, evident from the table.
b. Calculate the atomic mass for Iodine.
I-127: 127 x .80 = 101.6 amu
I-126: 126 x .17 = 21.42 amu
I-128: 128 x .03 = + 3.84 amu
= 126.86 amu ( atomic mass of Iodine)
c. What unit is used to express the atomic mass for elements? Atomic Mass Units Why did
scientists’ select this unit of measurement over the metric system? Because easier to
calculate the mass of an atom using amu then grams. Using grams requires scientific
notation values because atoms being so tiny.
d. What is the difference between Iodine’s mass numbers and Iodine’s atomic mass? The mass
number is literally the number of protons and neutrons in an atom, the mass of a single
atom. The atomic mass is the average mass of an element taking in to consideration all the
isotopes of that element.
e. Which iodine’s isotope occurs most common in nature? I-127 because it has a higher natural
abundance and Iodine’s atomic mass (126.86 amu) is closer to I-127’s mass number (127
amu)
15. Illustrate the atomic models for
Li-7:
p+ = 3
n= 4
e- = 3
Li-7 and Li-9
L-9
p+ = 3
n= 5
e-= 3
*Make sure you can illustrate the location of each of these subatomic particles within an atom.
*16.a. Identify the two types of forces within an atom.
Electrostatic attractive forces: forces between charged particles.
Nuclear forces: forces between protons and neutrons within the nucleus. Keeps the protons
and neutrons together in the nucleus.
b.Give an example of each type of force within the atom
 Electrostatic attractive forces between protons and electrons
 Electrostatic repulsion forces similar charged particles: protons and protons in the
nucleus; electrons and electrons in the electron cloud
b. Which force is weaker? Explain why this is true. Electrostatic forces within
an atom are weaker, because protons remain in the nucleus. If electrostatic
forces were stronger the protons and electrons would combine collapsing the
nucleus.
*