3.00_Chemistry of Biology Biology I (Ions) Slides 84-100

What’s an Ion? https://www.youtube.com/watch?v=WWc3k2723IM

Ions An atom usually has a neutral charge. That means it has the same number of protons as electrons Remember, a proton has a positive charge and an electron has a negative charge ION – an atom that has lost or gained one or more electrons and has become charged either positively or negatively

How do atoms form Ions An ion is an atom or group of atoms that has an electrical charge, either positive or negative. Atoms have an equal number of protons and electrons and so do not have an overall charge. Atoms with incomplete outer electron shells are unstable. By either gaining or losing electrons, atoms can obtain full outer electron shells and become stable, just like the noble gases. When this happens, atoms have an unequal number of protons and electrons and so have an overall charge. This is how atoms become ions.

Positive Ions When an atom LOSES electrons, it becomes more POSITIVE Why? If you are getting rid of negative particles (electrons) but your number of positive particles (protons) are staying the same. In other words, you are subtracting negative numbers

Positive Ions What would the charge be if: The neutral form of Gold (Au) lost 4 of its 79 electrons. It now has 79 protons and 75 electrons The neutral form of Mg lost 2 of its 12 electrons. It now has 12 protons and 10 electrons.

Negative Ions When an atom GAINS electrons it becomes more NEGATIVE Why? Electrons have a negative charge, so the more you have, the more negative you become

Ions Ions are represented by placing a “superscript” charge number next to the atomic symbol. Ex. O-2 = oxygen with a negative 2 charge K+ = potassium with a positive 1 charge N-3 = nitrogen with a negative 3 charge And so on

Isotopes or Ions

Isotopes or Ions How many P’s, N’s, and E’s does each of the following have? Label each as an isotope, ion, or the version found on the P.T.

What is a compound ion? Ions can be made up of a single atom or a group of atoms. An ion made up of a group of atoms is called a compound ion. What atoms are present in the following compound ions? Ion Formula Charge Atoms present O H hydroxide OH- S O O O O sulfate SO42- -2 nitrate NO3- -1 N O O O C O O O carbonate CO32- -2 N H H H H ammonium NH4+ +1

Naming Ions and Compound Ions There are two common types of ions: –ide ions and –ate ions. What is the difference? Generally, –ide ions are negatively-charged ions of an element, e.g. sulfide (S2-), fluoride (F-), oxide (O2-). The exception to this rule is the hydroxide ion, which contains both hydrogen and oxygen (OH-). –ate ions are negatively-charged compound ions that include oxygen, e.g. sulfate (SO42-), nitrate (NO3-), carbonate (CO32-).

Ions and Compound Ions IONS are atoms or groups of atoms with a positive or negative charge. Taking away an electron from an atom gives a CATION with a positive charge Adding an electron to an atom gives an ANION with a negative charge. 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 and Anions A CATION forms when an atom loses one or more electrons. An ANION forms when an atom gains one or more electrons Mg --> Mg2+ + 2 e- F + e- --> F-

Predicting Ion Charges metals (Mg) lose electrons ---> cations nonmetals (F) gain electrons ---> anions

Learning Check 39 K+ 16O -2 41Ca +2 19 8 20 #p+ ______ ______ _______ State the number of protons, neutrons, and electrons in each of these ions. 39 K+ 16O -2 41Ca +2 19 8 20 #p+ ______ ______ _______ #no ______ ______ _______ #e- ______ ______ _______

Learning Check Write the nuclear symbol form for the following atoms or ions: A. 8 p+, 8 n, 8 e- ___________ B. 17p+, 20n, 17e- ___________ C. 47p+, 60 n, 46 e- ___________

Charges on Common Ions -3 -2 -1 +1 +2 By losing or gaining e-, atom has same number of e-’s as nearest Group 8A atom.