1. Ions are formed by loss or gain of electrons.
QUESTION:
How many protons and electrons are in a nitride ion (N3-)? A. 7, 10, B. 7, 4, C. 10, 7, D. 4, 7
Ions are formed by loss or gain of electrons.
A negative ion is formed by gaining electrons.
A charge of -3 means a gain of 3 electrons.
N atom has 7 protons, 7 electrons.
N3- ion has 7 protons, 10 electrons
Charge = (#protons) – (#electrons)
= 7 – 10 = -3
SCRIPT:
How many protons and electrons are in a nitride ion (N3-)? A. 7, 10, B. 7, 4, C. 10, 7, D. 4, 7
PAUSE
Ions are formed by loss or gain of electrons.
The number you see written on the upper right hand corner
HIGHLIGHT 30
Is the charge of the charge of the ion.
CALLOUT “charge”
Remember that each electron has a negative one charge.
A negative charge is obtained by by gain electrons.
Therefore, a negative ion must have more electrons than protons.
Choices B and C are obviously wrong.
CROSS OUT choices B and C.
So how do we determine the number of protons and electrons in the ion? CLICK We refer to the periodic table. From the periodic table, we find that the atomic number of nitrogen is 7.
CLICK
The number of protons in a nitrogen atom is, therefore, 7.
Therefore, choice D, which is wrong.
CROSS OUT 4 in choice D.
Since an atom is neutral, a nitrogen atom also has 7 electrons.
CLICK A nitride ion is formed by gaining three electrons.
7 plus 3 equals 10.
Therefore… a nitride ion has only 10 electrons.
HIGHLIGHT 10.
But it still has 7 protons.
The correct answer is A.
Note that the charge of an ion is just equal to the number of protons minus the number of electgrons.
In the case of nitride ion, 7 minus 10, equals -3.
PAUSE CLICK END RECORDING

2. Video ID: © 2008, Project VALUE (Video Assessment Library for Undergraduate Education), Department of Physical Sciences Nicholls State University Author: Glenn V. Lo Narrator: Funded by Louisiana Board of Regents Contract No. LA-DL-SELECT-13-07/08