Cracking the SAT Chemistry Subject Test

CHAPTER 4 ATOMS: THE BUILDING BLOCKS

OF MATTER

Drill 1

1. A Helium is an element, and the smallest piece of an element is an
   atom. That’s why (A) is correct. An atom is the smallest particle of an
   element that still retains the properties of that element.


2. E You know that every electron carries a charge of −1, and that an
   atom becomes a positively charged ion when it loses an electron(s), and a
   negatively charged ion when it gains an electron. That’s why (E) is correct.


3. D Which of the components of the nucleus—protons or neutrons—
   have a positive charge? Protons have a positive charge, while neutrons have
   no charge—they are electrically neutral. The answer is (D).


4. C Don’t be fooled by the mention of uranium; it’s just another
   element. You know that isotopes of the same element do not differ in their
   number of protons, may differ in their number of electrons, but must differ
   in their number of neutrons. That’s why (C) is correct.


5. D The atomic number of an element depends on the number of
   protons in that element’s atoms, so the answer must be (D).


6. T, T, CE
   Divide and conquer! Evaluate the first statement
   without looking at the second, and decide whether it’s
   true or false. It’s true. The periodic table reports atomic
   weights but not mass numbers.
   Now see if the second statement is true or false. Is it
   true that a mass number can be assigned only to a single
   isotope of an element but not to an element in general?
   Yes. Mass number = number of protons + number of