The “Element”ary Exam Answer Key- Jenna Zukswert
Answers to the multiple choice:
1. ___b___ 2.___ c____ 3.___c___ 4.____a___ 5.___d____
6.____a___ 7.____b___ 8.___d____ 9.___d____ 10.__a____
11.___c___ 12.___d___ 13.___b___ 14.___a___ 15.___d___
16.___b___ 17.___c___ 18.___a___ 19.___d___ 20.___b___
Reactions
1.
Write equations for the ionization of Mg to Mg
+1
and Mg
+1
to Mg
+2
. Then, calculate the energy required to remove all valence electrons from one gram of magnesium. The first ionization energy is 738.1 kJ/mol, the second ionization energy is 1,450 kJ/mol, and the third ionization energy is 7,730 kJ/mol.
Mg (g) + 738.1 kJ → Mg +1 (g) + e -
Mg +1 (g) + 1,450 kJ → Mg +2 (g) + e -
1.00 g x (1 mol Mg)/(24.31g Mg) x (2188 kJ)/ (1 mol) = 90.0 kJ
* Use conversion factors to convert from grams to moles to kilojoules
2.
Write the equation for the formation of a fluoride anion from a fluorine atom.
Fluorine’s electron affinity is +328 kJ/mol, meaning that ΔH= -328 kJ/mol.
F (g) + e → F (g) + 328 kJ
ΔH = -328 kJ/mol, so for two moles of F, ΔH = -656 kJ

Writing Section- Answers
Short Answer (5 points each)-
Points that Should Be Included in Response to Receive Full Credit:
1.
Explain how the modern periodic table came to be. Reference Moseley,
Newlands, and Mendeleev in your answer.
Newlands developed the Law of Octaves , realizing that every eighth element exhibits similar qualities
Mendeleev made a better periodic table of the elements arranging them by patterns he noticed in properties. It was more accurate than Newlands and he was able to predict the existence of then-unknown elements
Moseley helped scientists realize that t he table should be ordered by atomic number instead of atomic mass by realizing a correlation between the frequency of X-rays emitted when an element is bombarded by electrons and the atomic number.
2.
What is ionization energy? How does ionization energy influence the type of ion that an element typically forms?
Ionization energy is the energy needed to remove an electron from an atom.
If an element has a low ionization energy, it requires less energy to remove an electron. These elements more readily form cations. Likewise, elements with high ionization energies require more energy to remove an electron.
Therefore, these elements more readily form anions.

3.
What is effective nuclear charge? How does it affect the size of an element’s atomic radius?
Effective nuclear charge is the charge of the nucleus that is felt by the valence electrons . The effective nuclear charge is influenced by the actual nuclear charge (the atomic number, number of protons) and the number of electrons in lower levels that repel the outer electrons and partly shield them from the actual nuclear charge .
The smaller the effective nuclear charge, the larger the atom . Since the electrons are not as tightly held to the nucleus , they may be located farther from the nucleus.
As the atomic number increases across a period , but the number of shielding electrons remains constant, the atom becomes smaller because the effective nuclear charge increases and the electrons are more tightly held to the nucleus.
Essay (15 Points)
Elements found in the same groups tend to share many of the same characteristics. a.
Describe the properties of the alkali metals b.
Describe the properties of the coinage metals c.
Compare and contrast the alkali metals and the coinage metals
Response should include most, if not all, of these points for each sub-prompt:
(student graded on amount of accurate information present in response) a.
– one valence electron in s orbital
never found isolated in nature, very reactive
reacts with water to form metal hydroxide
first column of the periodic table
low ionization energy

b.
– one valence electron in s orbital, but a full d orbital
copper, silver, gold, 1 B metals
high ionization energy
transition metals, 1 B column
very un-reactive, usually found uncombined in nature (used in coins, etc. c.
– They have similar electron configurations (both have one valence electron)
Different chemical properties due to presence or lack of a filled d orbital.
Noble gas cores of alkali metals shield the alkali metal valence electrons more completely than the filled d orbitals, so the 1B valence electrons are more strongly attracted to the nucleus
Restate some of the differences (high v. low ionization for reason above, difference in reactivity because of electron configuration, etc.)
Main Points of Essay (it should be evident that the student understands this): electron configuration determines chemical behavior , and elements in the same families have similar electron configurations thus they have similar properties.
Multiple Choice Question Topics:
Ionization Energy: questions 2, 6, 14, 18
Electron Affinity: questions 3, 7, 11, 13
Atomic radius/ effective nuclear charge: questions 1, 5, 10, 16
Element Characteristics and Families: questions 4, 12, 15, 19
Electron Configuration and Other.: questions 8, 9, 17, 20

Increasing atomic radius
Increasing ionic radius
Decreasing ionization energy
Decreasing electronegativity
Periodic Table Trends
Decreasing Cation Radius
Decreasing Atomic Radius
Decreasing Anion Radius
(starting at N)
Increasing ionization energy Increasing electronegativity
Rep.
Elements
Metals
Transition Metals
Metals
Representative
Elements
Metals, Metalloids,
Nonmetals
Inner Transition Metals
(Lanthanide and Actinide)
Metals
Alkali metals
Other things that may be labeled (additional credit may be given if the instructor chooses to allow it):
Alkaline Earth Metals (2A)
Coinage metals (1B)
Stair-step line that divides metals and nonmetals (surrounded by metalloids and aluminum)
Chalcogens (6A)
s, p, d, and f orbitals i.
s= 1A, 2A ii.
p= 3A-8A iii.
d=transition metals iv.
f= inner transition metals
Noble
Gases