Paper 1 · November 2020 · Atomic Structure and Bonding
The table shows information about the subatomic particles of two species, X and Y.
| element | number of electrons | number of neutrons | number of protons |
|---|---|---|---|
| X | 4 | 6 | 5 |
| Y | 6 | 4 | 5 |
Which statement about X and Y is correct?
AThey are both positively charged.
BThey have the same mass number.
CThey represent the same element.
DThey are both negatively charged.
Explanation
Both species have 5 protons, and the proton number is what fixes the element, so X and Y are the same element, boron. X has 4 electrons to 5 protons, so it is positively charged; Y has 6 electrons to 5 protons, so it is negatively charged, which rules out A and D. Their mass numbers are 5 + 6 = 11 and 5 + 4 = 9, which are different, so B is wrong.
ZIMSEC Chemistry 4024/1, November 2020, Q1