Chemistry Unit 3: Bonding <3

Same group = similar valence electrons = same properties = form similar ions and have similar roles in ionic compounds

Octet rule: 8 electrons = full

Halogens have 7 valence electrons, so rlly want one more -> most of the time -1 charge (anion)

E.x. fluoride anion, chloride anion

6 valence electrons, similar, want to get 2 more electrons -> most of the time -2 charge (anion)

E.x. oxide anion, sulfide anion

Alkali metals have only 1 valence electron, rlly want to get rid of -> +1 charge (cation)

E.x. sodium, potassium with positive one charge

Alkali earth metals -> +2 charge, magnesium, calcium, etc

Hydrogen is an exception! Can be +1 or -1 charge bc only one electron to lose/gain for a “full shell”

Ionic Bonds

Ionic bond when Opposite charges attract!, between metal and nonmetal forms ionic compound

Example: Halogen + Alkali metal ( -1 and +1 ions)

Ex. lithium (+1) + chloride (-1) -> lithium chloride

      Sodium (+1) + chloride (-1) -> sodium chloride (table salt)

Can also have different amts of ions for each element. Just have to have neutral charge

Ex. Calcium iodide (two iodine ( each -1 = -2) and one calcium (+2))

Naming

Sodium chloride

^                    ^

Cation           Anion

Polyvalent ions

D-block elements how to name? Look at the anion.

Ex. cobalt sulfide. Sulfide is -3 so cobalt must be +3. Write as cobalt (III) sulfide

Polyatomic ions

These are covalently bonded groups of atoms that act as an ion with a net charge. Still form ionic bonds with other ions. Bond in a ratio. Use parentheses around if multiple

Example: ammonium sulfate

Covalent bonds: SHARE electrons, between two nonmetals

E.x. O2 (Diatomic element: element that doesn’t exist alone in nature as an individual

Water (H2O)

Oxygen pulls the pair closer to it tho, makes it’s side more negative. Polar molecule

Lewis structures

- means an electron pair, a bond

Lone pair: two dots, no covalent bond

Molecules, salts, compounds, and chemicals?

Molecule: group of two or more atoms covalently bonded together

Covalent network solids: covalently bonded substance that doesn’t consist of molecules, instead a network

E.x. silica (SiO₂) 

Connected in a network, rather than a molecule

One grain of sand is a giant molecule

Salt: cations and anions ionically bonded to each other

E.x. NaCl, table salt

Ionic solids are arranged in a crystal lattice structure, so that the charges work out

Compound: a chemical substance composed of two or more different elements. Either covalently or ionically bonded

Covalent compounds and ionic compounds

Chemical: any substance with a definite composition

Metallic bond:

Sea of valence electrons. Occurs between two metals. Allows electricity/conductivity and property of malleability