Ions

IONS IONS are atoms that have lost or gained electrons to have an electrical charge. The number of protons does not change in an ion The number of neutrons does not change in an ions So, both the atomic number and the atomic mass remain the same. To tell the difference between an atom and an ion, look to see if there is a charge in the superscript! Examples: Na+ Ca+2 I- O-2 Na Ca I O

Forming Cations A CATION forms when an atom loses one or more electrons. Therefore, the charge of the atom will be positive! In general, metals will lose electrons to form a cation.

Forming Anions An ANION forms when an atom gains one or more electrons. Therefore the charge will be negative. In general, non-metals will gain electrons to form anions.

To determine if it is a cation or anion: Look at the charge Positive charge: lost electrons Negative charge: gained electrons Look at the number: this is how many were gained or lost

Example: Ion Gaining/Losing How Many Cation or Anion Ca2+ Al3+ S2- Li+ For the following ions, determine if they are gaining or losing electrons, how many and if they form a cation or anion. Ion Gaining/Losing How Many Cation or Anion Ca2+ Al3+ S2- Li+ Br-

Brain Break: Line Up Birthday Favorite Color Favorite Food

Learning Check – Counting State the number of protons, neutrons, and electrons in each of these ions. 39 K+ 16O -2 41Ca +2 #p+ ______ ______ _______ #no ______ ______ _______ #e- ______ ______ _______

Learning Check-Symbols Determine if the following elements are a cation or anion. Then, write the nuclear symbol for each. A. 8 p+, 8 n, 6 e- ___________ B. 17p+, 20n, 18e- ___________ C. 47p+, 60 n, 45 e- ___________

One Last Learning Check Draw a Bohr model for the following ions. B3+ P3- Na+

Charges on Common Ions -1 -2 -3 +1 +2 +3 By losing or gaining e-, an atom has the same number of e-’s as the nearest Group 18/8A (Noble Gases) atom. The ion that an element will form can be predicted from the periodic table! +3