Unit 6 Ch 9 Part 2 Notes Ions and Ionic bonding 9.1

Bellwork, Wednesday How many protons, neutrons and electrons are in this atom? Based on what you know about the charge of a proton and an electron, what is the overall charge of this atom? What element is this atom? Red =protons Yellow=neutrons Black=electrons

Ions- atoms or groups of atoms that have a positive or negative charge Ions- atoms or groups of atoms that have a positive or negative charge. Ions are formed when one or more electrons are lost or gained.

Let’s Practice! Sodium loses an electron Na  __________ Magnesium loses two electrons Mg  __________ Chlorine gains one electron Cl  __________ Phosphorus gains three electrons P  __________

We are positive about metal cats! Cation- -positively charged ion -electrons were lost -metals tend to form cations -name of monatomic cation is the same as the element We are positive about metal cats!

Examples: Na  Na+ + e- Ca  Ca2+ + 2e- Fe  Fe3+ + 3e-

We feel negatively about ants! Anion - negatively charged ion -electrons were gained -nonmetals tend to form anions -name of monatomic anion ends in –ide We feel negatively about ants! Examples:

Ionic compound- -composed of cations and anions -usually metal & nonmetal -electrically neutral -mostly solids at room temperature -high melting points -the more positive element always comes first -Ex NaCl, NaF, CaCl2

Monatomic Ions The charge of a monatomic ion can often be determined by the element’s position on the periodic table: Group 1A: 1+ Ex. Na+ Group 2A: 2+ Ex. Ca2+ Group 3A: 3+ Ex. Al3+ Group 5A: 3- Ex. N3- Group 6A: 2- Ex. O2- Group 7A: 1- Ex. F-

The carbon family has a charge of + or -4 Alkali metals have a charge of +1 The boron family has a charge of +3 Alkaline Earth metals have a charge of +2 Transition metal charges will need to be memorized!

Elements in Group 18 (8A) do not form ions Elements in Group 18 (8A) do not form ions. Elements in Group 4 rarely form ions. They tend to react by sharing electrons (forming covalent compounds) instead of transferring electrons. Group 8 Electron configuration = s2p6 Group 4 Electron configuration = s2p2

What causes the charges for each group on the periodic table? The charges indicate how many electrons an atom will gain or lose. If it loses 2, the charge will be +2. If it gains 2, the charge will be -2. Remember that electrons are NEGATIVE!

Octet Rule and Stability The goal of an atom is to become stable. An atom will gain, lose, or share electrons in order for that stability to be attained. Stability is determined by the octet rule: Most atoms want 8 valence (outer shell) electrons in order to become stable.

Ex: Potassium (and all of group 1) has 1 valence electron, so it will lose 1 electron making its charge +1. Remember that electrons are NEGATIVE!

Examples: O P F Na Mg Al Sr 2- 3- 1- 1+ 2+ 3+ 2+

Transition Metal ions: Most transition metals form more than one ion Transition Metal ions: Most transition metals form more than one ion. They are stable losing varying numbers of electrons. The possible charges must be memorized.

Exceptions: Zinc and Cadmium will always be 2+ and Silver will always be 1+.

What is the formula for the following transition metals as ions? Copper (I) Iron (III) Lead (II) Manganese (III)

The mercury(I) ion is unique The mercury(I) ion is unique. It only exists in pairs of mercury(I) ions (like Siamese twins). Its symbol is Hg22+.

Quick Check Quiz: Have you been studying your ions Quick Check Quiz: Have you been studying your ions? sodium _______ chromous ________ selenide _______ tin(IV) ________ Na+ Cr2+ Se2- Sn4+

Polyatomic Ions -tightly bound groups of atoms that behave as a unit and carry a charge -atoms are bound together by shared electrons

The only positively charged polyatomic ion that we need to memorize is ammonium, NH4+.

Ions that end in –ite or –ate contain oxygen Ions that end in –ite or –ate contain oxygen. In a series such as sulfate and sulfite, the –ite ending has one less oxygen than the –ate ending. Sulfite SO32- Sulfate SO42-

SO32- sulfite SO42- sulfate NO2- nitrite NO3- nitrate EXAMPLES SO32- sulfite SO42- sulfate NO2- nitrite NO3- nitrate