The table gives the number of protons, neutrons and electrons in four species labelled p, q, r and s. Some of the species are atoms and some are ions. speci...
Question 1 Report
The table gives the number of protons, neutrons and electrons in four species labelled p, q, r and s. Some of the species are atoms and some are ions.
| species | protons | neutrons | electrons |
|---|---|---|---|
| p | 11 | 12 | 11 |
| q | 11 | 12 | 10 |
| r | 8 | 8 | 10 |
| s | 20 | 20 | 18 |
(a) State which species is a neutral atom. [1]
(b) Deduce the charge on species q. [1]
(c) Deduce the charge on species r. [1]
(d) Deduce the charge on species s. [1]
(e) State which two species have the same electronic configuration. [1]
(f) State the electronic configuration of species s. [1]
(g) Species p and q have the same proton number. State whether they are the same element. [1]
(h) Calculate the nucleon number of species p. [1]
(i) Name element p. [1]
(j) Species r is formed when an atom gains electrons. State the name given to a negatively charged ion. [1]
Answer Details
This question tests the difference between an atom and an ion. Charge is decided by comparing protons (fixed, positive) with electrons (variable, negative): equal numbers means neutral, fewer electrons means a positive ion, more electrons means a negative ion.
- (a) A neutral atom has equal protons and electrons. Only species p has 11 protons and 11 electrons, so p is the neutral atom [1].
- (b) Species q has 11 protons but only 10 electrons: one more positive charge than negative, giving a charge of 1+ [1].
- (c) Species r has 8 protons and 10 electrons: two more electrons than protons, giving a charge of 2- [1].
- (d) Species s has 20 protons and 18 electrons: two more protons than electrons, giving a charge of 2+ [1].
- (e) Electronic configuration depends on the number of electrons. Species q has 10 electrons (2,8) and species r has 10 electrons (2,8), so q and r share the same configuration [1].
- (f) Species s has 18 electrons, filling the shells as 2, 8, 8, so its configuration is 2,8,8 [1].
- (g) An element is defined by its proton number. Species p and q both have 11 protons, so yes, they are the same element (one is the atom, one is its ion) [1].
- (h) Nucleon number of p = protons + neutrons = \( 11 + 12 = 23 \) [1].
- (i) Proton number 11 is sodium [1].
- (j) A negatively charged ion is called an anion [1] (a positive ion is a cation).
Exam tip: the proton number never changes for a given element; only the electron count changes to make an ion, so compare protons with electrons to get the charge.
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