Topic 1 - Matter and Energy - Revsworld

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Topic 3 – The Atomic Structure
36. Ions: Determining and comparing number of particles and size of ions to neutral atom
Concept Task: Be able to determine differences and /or similarities in the number of particles between
an ion and a neutral atom.
Study the information below.
To determine difference in electrons:
Consider the following comparisons.
A Positive ion always has FEWER electrons than the neutral atom
The difference in number of electrons is equal to the value of the charge.
Ex. Na + ion has 1 LESS electron than neutral Na atom
A Negative ion always has MORE electrons than the neutral atom
The difference in number of electrons is equal to the value of charge.
Ex. S 2- ion has 2 MORE electrons than neutral S atom
NOTE: Both the ion and the neutral atom always have the SAME number of protons
Study example multiple choice questions below.
NOTE: In questions, PAY ATTENTION to what is being compared to what.
Example 31
Compare to Na , Na + has
1) 1 more protons 2) 1 fewer protons 3) 1 more electrons 4) 1 fewer electrons
Answer: Choice 4 (see sodium atom and ion diagrams on the last page)
Example 32
How does the size of Na atom compares to Na + ?
1) Na is bigger than Na + because Na has fewer electrons
2) Na is bigger than Na + because Na has more electrons
3) Na is smaller than Na + because Na has fewer electrons
4) Na is smaller than Na + because Na has more electrons
Correct: Choice 2. (see sulfur atom and ion diagrams on the last page)
Example 33
Compare to S 2- , S has
1) 2 more protons 2) 2 fewer protons 3) 2 more electrons 4) 2 fewer electrons
Answer: Choice 4
(see sulfur atom and ion diagrams on the last page)
Example 34
How does the size of S 2- ion compares to S?
1) S 2- is bigger than S because S 2- has more electrons
2) S 2- is bigger than S because S 2- has less electrons
3) S 2- is smaller than S because S 2- has more electrons
4) S 2- is smaller than S because S 2- has less electrons
Answer: Choice 1
(see sulfur atom and ion diagrams on the last page)
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