All GRE Subject Test: Chemistry Resources
Example Questions
Example Question #1 : Periodic Table Groupings
An unknown element has been studied in the lab. It has been shown to be malleable, ductile, and a good conductor of heat. Which element best fits this description?
Silicon
Cobalt
Sulfur
Boron
Cobalt
The correct answer is cobalt, since it is the only metal among the answer choices. Metals have all the properties described (malleability, ductility, and conductivity). Sulfur, boron, and silicon do not exhibit these properties to the same extent.
Example Question #2 : Elements And The Periodic Table
There is a unknown element in a jar. It is a solid at room temperature and conducts electricity. Which of the following could be true about this element?
The identity of the element is silicon and it is a good oxidizing agent
The identity of the element is silicon and it can be stretched to create a thin wire
The identity of the element is sodium and it is a good oxidizing agent
The identity of the element is sodium and it can be stretched to create a thin wire
The identity of the element is sodium and it can be stretched to create a thin wire
The question states that the element is a solid at room temperature and conducts electricity. These are characteristics of a metal; therefore, the element is likely a metal. Recall that metals are usually found on the left side of the periodic table. The groups that are classified as metals include the alkali metals (group 1), alkaline earth metals (group 2), the aluminum family (group 3), and the transition metals (D block).
The answer choices state that it could be either sodium or silicon. Silicon is in group 14 and is considered a non-metal; therefore, the element has to be sodium. Metals are good electrical conductors and solid at room temperature. They are also ductile, which means that a metal can be stretched to create thin wires.
Metals are good reducing agents, not oxidizing agents. Recall that metals usually have one, two, or three valence electrons. Since they only have a few valence electrons, metals prefer to lose their valence electrons to complete an octet. When an element loses electrons it is considered to be oxidized and can act as a reducing agent; therefore, sodium is not an oxidizing agent.
Example Question #1 : Gre Subject Test: Chemistry
What class of element is zinc?
Metalloid
Transition metal
Non-metal
Alkali metal
Transition metal
In general, the metals fall on the left side of the periodic table and are separated from the non-metals by the metalloids. Transition metals fall in the d block of the periodic table, in groups (columns) 3-12. Examples of metals, non-metals, transition metals, and metalloids are calcium, oxygen, zinc, and arsenic, respectively.
Alkali metals are a special class of metal only found in group 1 of the periodic table.
Example Question #935 : Mcat Physical Sciences
The multiple oxidation states of transition metals are due to which of the following properties?
The weak attraction between the nucleus and its core electrons
The large number of valence electrons
The instability of the p orbitals
The presence of incomplete d orbitals
The presence of incomplete d orbitals
The transition metals are defined in the region of the periodic table in which atoms are being added to the d subshell. As a result, the transition metals have unfilled or incomplete orbitals within the d shell. Since each orbital is filled with one electron before orbitals start to become completely filled, there are increasing numbers of unpaired d shell orbitals. This allows transition metals to give up variable numbers of electrons, while maintaining stability, as electrons move between d orbitals.
A common example is iron, which is stable in both the and
electron configurations.
Example Question #21 : Periodic Table Groupings
Which of the following is true about transition metals?
I. Transition metals form acidic oxides
II. A transition metal can have multiple oxidation states
III. Transition metals can be reduced, but can never be oxidized
I, II, and III
II only
I only
I and II
II only
Transition metals are classified as metals; therefore, the oxides they form are called metal oxides. Metal oxides are basic compounds, whereas non-metal oxides are acidic compounds. Metal oxides, such as and
, give rise to high pH values, and non-metal oxides, such as
and
, give rise to low pH values.
An oxidation state is defined as the degree of oxidation a compound can achieve. It is often calculated by observing the gain and loss of electrons in an atom. For example, an atom that loses two electrons will have an oxidation number of , whereas an atom that gains two electrons will have an oxidation number of
. Some transition metals have multiple oxidation states because they can lose varying amounts of electrons. This occurs because the energy difference between the outermost
orbital and the outermost
orbital is small; therefore, the energy required to remove the electron from the subsequent
orbital is comparable to removing electrons from the
orbital.
For example, iron () can have an oxidation state of
or
. Iron’s electron configuration is
. When it loses two electrons, iron will have an empty
orbital. The electron configuration of
will be
. The amount of energy difference between the
orbital and the
orbital is very small; therefore, it is easy for iron to lose another electron from the
orbital and become
. On the other hand, it is very hard to remove electrons from a filled
orbital. This explains why non-metals, such as the oxygen and halogen groups, and metals, such as alkali and alkaline earth metals, have only one oxidation state.
Reduction involves gaining electrons and oxidation involves losing electrons. This means that reduction will decrease the oxidation number and oxidation will increase the oxidation number. It is generally favorable for a transition metal to lose electrons and become oxidized, though reduction can be achieved by adding enough energy to the system (such as in a electrolytic cell).
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All GRE Subject Test: Chemistry Resources
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