1. Ions are formed by loss or gain of electrons.
QUESTION:
A magnesium atom becomes a magnesium ion (Mg2+) by… A. gaining two electrons, B. losing two electrons C. gaining two protons, D. losing two protons
Ions are formed by loss or gain of electrons.
A positively-charged ion is formed by losing electrons.
A charge of +2 means a loss of two electrons.
Standard way of indicating positive charges:
+, 2+, 3+, etc.
In older textbooks, you may see Mg++ or Mg+2
SCRIPT:
A magnesium atom becomes a magnesium ion (Mg2+) by… A. gaining two electrons, B. losing two electrons C. gaining two protons, D. losing two protons
PAUSE
CLICK Ions are formed by loss or gain of electrons.
So, immediately, we can rule out choices C and D.
CROSS OUT C and D
CLICK
A positively-charged ion is formed by losing electrons.
The number you see written on the upper right hand corner
HIGHLIGHT 2+
Is the charge of the ion.
Therefore, the ion given here ---- magnesium ion --- is a positive ion.
It is formed when a magnesium atom loses two electrons.
The correct answer is B.
Note… the standard way of indicating positive charges is to write + if the charge is +1,
HIGHLIGHT 2+ if the charge is +2
HIGHLIGHT 3+, if the charge is +3,
And so on….
With older textbooks, however, you may see a +2 charge indicated with two pluses,
HIGHLIGHT ++ in Mg++
Or with the plus sign in front of the number.
HIGHLIGHT +2 in Mg+2
CLICK PAUSE 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