Lecture 3 notes.docx - CHM153 Lecture 3 Name: Marise Daphne...

CHM153 Lecture 3 Name: Marise Daphne Dibgolongo
Atoms are neutral #p+=#e-
Ions:
-Atoms can become charged by losing or gaining electrons.
-When there is a different number of protons and electrons, the
atom has a net charge and is called an ion:
Cation: #e-<#p+which means there is positive charge so the
charge is pawsitive ( loses e-)
Anion: #e->#p+ which means atom gains e-. There is more
negative charge leading to a negative charged ion. The #p+ stays
the same
One reoccurring trend in the groups (columns) of the periodic
table is how many electrons atoms tend to lose/gain.
1
st
column (1a): Alkaline metals tend to lose 1e- single valent
Na atom Na+ ion
11p+,11e- 11p+,10e-
2 nd Column (2a): tend to lose 2e-
1

CHM153 Lecture 3 Name: Marise Daphne Dibgolongo
Ca atom Ca ion
20p+, 20e- 20p+, 18e-
The charge are valence: this a divalent
3
rd
from right (6a):tend to gain 2e-
O atom O^2- ion
8p+,8e- 8p+,10e-
2
nd
from right (7a): tend to gain 1e-
Cl atom Cl- ion
17p+,17e- 17p+, 18e-
Rightmost (8a): don’t tend to lose or gain
Atoms tend to lose/gain the number of electrons that separates
them from the noble gas column
2