While researching a topic, a student has taken the following notes:Some atoms contain an excess of neutrons.Often, these neutrons form...
GMAT Expression of Ideas : (Expression) Questions
While researching a topic, a student has taken the following notes:
- Some atoms contain an excess of neutrons.
- Often, these neutrons form a 'skin' on the atom's surface.
- An atom of lead-208 has a neutron skin.
- The thickness of its neutron skin is approximately 0.28 trillionths of a millimeter.
The student wants to emphasize the thickness of lead-208's neutron skin. Which choice most effectively uses relevant information from the notes to accomplish this goal?
The neutron skin surrounding an atom of lead-208 measures about 0.28 trillionths of a millimeter.
Atoms with excess neutrons will often acquire a neutron skin.
An atom of lead-208, like some other atoms, is surrounded by a neutron skin.
Neutrons surround the surface of an atom of lead-208.
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Some atoms contain an excess of neutrons." |
|
| "Often, these neutrons form a 'skin' on the atom's surface." |
|
| "An atom of lead-208 has a neutron skin." |
|
| "The thickness of its neutron skin is approximately 0.28 trillionths of a millimeter." |
|
Part B: Provide Passage Architecture & Core Elements
Visual Structure Map:
[GENERAL CONCEPT] Some atoms have excess neutrons → [WHAT HAPPENS] Neutrons form skin on surface → [SPECIFIC EXAMPLE] Lead-208 has neutron skin → [PRECISE MEASUREMENT] Thickness = 0.28 trillionths mm
Main Point: Lead-208 is a specific example of an atom with excess neutrons that form a measurable neutron skin on its surface.
Step 2: Interpret the Question Precisely
What's being asked? We need to choose which option most effectively emphasizes the thickness of lead-208's neutron skin.
What type of answer do we need? A sentence that highlights or draws attention to the measurement aspect of the neutron skin.
Any limiting keywords? None specified.
Step 3: Prethink the Answer
- To emphasize thickness, we need the specific measurement - that's the only quantitative detail that actually shows how thick the neutron skin is
- The right answer should include 0.28 trillionths of a millimeter because without that number, we can't emphasize thickness at all
The neutron skin surrounding an atom of lead-208 measures about 0.28 trillionths of a millimeter.
✓ Correct
- Includes all key elements: lead-208, neutron skin, and the precise measurement
- The phrase measures about 0.28 trillionths of a millimeter directly emphasizes thickness through quantification
Atoms with excess neutrons will often acquire a neutron skin.
✗ Incorrect
- Focuses on general information about atoms with excess neutrons
- Contains no measurement or thickness information at all
An atom of lead-208, like some other atoms, is surrounded by a neutron skin.
✗ Incorrect
- Mentions lead-208 and neutron skin but omits the crucial thickness measurement
- Without the measurement, there's no emphasis on thickness
Neutrons surround the surface of an atom of lead-208.
✗ Incorrect
- Provides very general information about neutrons surrounding lead-208
- No mention of skin concept or thickness measurement