Chapter 3A chemical bonds- what holds compounds together -bonds can be ionic or molecular/covalent chemical formula- shows the kinds and number of each element in a compound ex- H 2 OCO 2 H 3 PO 4 structural formula- uses lines to show bonds ex- OO ═ C ═ O H

empirical formula- gives the relative number of atoms of each element in a compound -lowest whole number ratio molecular formula- gives the actual number of atoms of each element in a compound ex- hydrogen peroxide H2O2H2O2 emp. = HO (H and O in a 1:1 ratio) mol. = H 2 O 2 page 87 Ex 3.1 and FP 3.1

atomic elements- exist in nature as single atoms -almost all the elements can exist as atoms -called monatomic molecular elements- cannot exist in nature as one atom, cannot exist alone -exist as molecules H O N Cℓ Br I F -called diatomic

Ions- particles with a charge (+ or -), they have either lost or gained electrons -in ions # of p + ≠ # of e - cation -ion with a positive charge -loses electrons -metallic elements lose electrons -look at Group # to get the charge for Groups 1A to 3A

ex- sodiumNa 1+ or Na +1 or Na + aluminumAℓ 3+ -sodium lost 1e-, aluminum lost 3 e - **Most cations of the transition metals have more than one charge -these will need to be given to you ex- Pb 4+ lost 4e - -a few have only one charge Ag 1+ Zn 2+ Cd 2+ -silver lost 1e-, zinc and cadmium each lost 2e -

anions -ion with a negative charge -gains electrons -non-metallic elements gain electrons -look at Group # - 8 to get the charge ex- chlorineCℓ 1- arsenicAs 3- -chlorine gained 1e - -arsenic gained 3e - *Group 4 elements do not generally form ions, Group 8 do not b/c they are inert

Naming Ions Cations -name is the same as the element with the word ion -back to examples sodium ionaluminum ionlead (IV) ion Anions -drop ending and add –ide and the word ion -back to examples -chloride ion -arsenide ion

Try these!! -name the ion/tell if it is a cation or anion -tell the charge on the ion -tell how e - the ion has lost or gained SrICaK PBSPBS polyatomic ions- made up or two or more atoms that carry a charge *most names end in –ite or –ate

Ionic Compounds -compounds composed of cations and anions -made up of a metal (cation) and a non-metal (anion) -usually solid crystals at room temp -have high melting points -are electrically neutral because # of p+ = # of e - ex- NaCℓKICa 3 N 2 formula unit- chemical formula for an ionic compound

Molecular Compounds -made up of two or more non-metals Binary Molecular Compounds -made up of two non-metals Ex- CO, CO 2, CCℓ 4 -to name molecular compounds you use prefixes

Prefix# (subscript) mono-1 di-2 tri-3 tetra-4 penta-5 hexa-6 hepta-7 octa-8 nona-9 deca-10

Naming Molecular Compounds -look at subscript of each element and give each element a prefix -if first element has a 1 as the subscript, then it does not get a prefix (omit mono-) -second element gets prefix and ends in –ide -if element begins with a vowel, drop the vowel at the end of a prefix **when writing formulas for molecular compounds you DO NOT reduce subscripts

Try these!! carbon monoxidecarbon tetrachloride sulfur trioxidetetriodine nonoxide phosphorus pentafluoride N 2 OPCℓ 3 SF 6 OF 2 CℓO 8 NF 3 S 2 Cℓ 2 N 2 O 4

Acids -acids are compounds dissolved in water -will have (aq) after the formula which means aqueous or dissolved in water -always begin with hydrogen (H) Ex- HCℓH 2 SO 4 H 3 PO 3 Naming Acids -you must look at what follows the hydrogen

-if it is a single element (ends in –ide), then you use prefix hydro-, root of the element, -ic ending and the word acid ex- HCℓ hydrochloric acid -if what follows hydrogen ends in –ite, you just add –ous ending to root of the polyatomic ion and add acid ex- H 3 PO 3 phosphorous acid

-if what follows hydrogen ends in –ate, you just add –ic ending to root of the polyatomic ion and add acid ex- H 2 SO 4 sulfuric acid Try these!! HIH 2 SH 2 CO 3 H 2 SO 3 HNO 2 HCℓO 3