Bonding Notes

An ion is an atom with a charge. Which atoms form cations and which form anions? H is not a metal ! NON-METALS form ANIONS (-) METALS form CATIONS (+)

Ions form charges because of their number of valence electrons!!!

Valence electrons = are the electrons in the highest occupied energy level (s & p) of an element

Quick Trick for Valence e- The group number tells the # of valence e--Group 1 (1A) has one valence electron -Group 2 (2A) has two valence electron Group 13 (3A) has three valence electrons Group 15 (5A) has five valence electrons Group 17 (7A) has seven valence electrons Group 18 (8A) has eight valence electrons (except Helium which has two.

Na + Group number? 1A Electron configuration? 1s2 2s2 2p6 3s1 Period? [Ne] 3s1 Valence electrons Cation or anion (loss or gain of e-)? [He] 2s22p6 Why?

Ca 2+ Group number? 2A Electron configuration? [Ar] 4s2 Period? 4 Valence electrons Period? 4 Cation or anion (loss or gain of e-)? [Ne] 3s23p6 Why?

S 2- Group number? 6A Electron configuration? [Ne] 3s2 3p4 Period? 3 Valence electrons Period? 3 Cation or anion (loss or gain of e-)? [Ne] 3s23p6 Why?

Practice Page 9 charges of Ion Worksheet

Octet Rule = In forming compounds, atoms tend to achieve the electron configuration of a noble gas*

Octet Rule Noble gas atoms are unreactive because their electron configurations are especially stable. This stability results from the fact that the noble-gas atoms’ outer s and p orbitals are completely filled by a total of eight electrons. Other atoms can fill their outermost s and p orbitals by sharing electrons through bonding. Such bond formation follows the octet rule: Chemical compounds tend to form so that each atom, by gaining, losing, or sharing electrons, has an octet of electrons in its highest energy level.

Lewis Electron Dots A visual representation of the valence electrons of the atom. The inner electrons and the nuclei are represented by the element’s symbol. The dots representing the electrons are arranged symmetrically around the symbol. Chemical bonds are formed between atoms using the unpaired valence electrons.

We can represent the number of valence electrons in a pictorial representation called Electron Dot Diagrams

Now you practice!! Read the directions and complete the worksheet- pg 19 --Valence e- and the Periodic table worksheet

chemical bonds form electrical attraction. A chemical bond is a mutual electrical attraction between the nuclei and valence electrons of different atoms that binds the atoms together Ionic bonding: Metal + Nonmetal (Cation + Anion) chemical bonds form electrical attraction. atoms GIVE UP electrons to other atoms. Form an “Ionic Compound” Covalent bonding: Nonmetal + Nonmetal SHARING of electrons between atoms. Form a “Molecular Compound” Tricky—covalent bond but molecular compound!!

Ionic Compound Formula Unit (Example:NaCl) Called Ionic bond & Ionic Compound Made of metal and nonmetal (cation & anion) Complete transfer of electrons Na+ + Cl- = NaCl electrically neutral salts -minerals in the earth’s Formula Unit (Example:NaCl) a chemical formula of the smallest sample of an ionic compound

Properties of ionic compounds Crystalline solids (salts) Ions sit ‘shoulder to shoulder’ High melting points (800ºC for NaCl- hard to break bonds) Conduct electricity in solution High boiling points Break easily (brittle) Many dissolve easily in water - ions separate

Ionic Bond = Electrons are transferred from one atom to another.

Molecular Compounds/ Covalent Bonds

Molecular Compounds-Covalent Bonds e- are shared between nonmetal atoms Most atoms achieve complete octet

Properties of Molecular Compounds Non-metal + Non-metal = covalent bond 2 non-metals SHARE e- to become stable like noble gases (think: hold hands) low melting & boiling points (below 300ºC) solid, liquid, or gas at room temp. Molecular Formula: carbon dioxide: CO2 & water: H2O Molecules form shapes

Covalent Bonds Covalent bonding—the sharing of electrons between two nonmetals. This creates a molecular compound or molecule. The goal is to attain eight valence electrons—stability Do not forget that hydrogen is a nonmetal.

Multiple Covalent Bonds Single bond—formed when one pair of electrons is shared between two atoms. Example H2 Double bond—involves two shared pairs of electrons. Example Ethene C2H4 Triple bond—involves three shared pairs of electrons. Example N2

Diatomic Molecules: atoms that bond with themselves Nitrogen—N2 Oxygen—O2 Fluorine—F2 (All the halogens) Chlorine—Cl2 Bromine—B2 Iodine—I2 Hydrogen—H2 Note: These molecules start with the atomic number seven & form the shape of the number seven on the PT. Don’t forget hydrogen in the upper left corner.

Practice Lewis Compounds Ionic Bonding activity- page 20 & 21 Do page 20 together