Chp 2 Atoms, Molecules & Ions

2.1 Early Ideas in Atomic Theory

Dalton’s Atomic Theory

1. matter made out of atoms

2. elements are only made out of one type of atom

3. atoms from one element differ from atoms from all other elements

4. compounds. two or more atoms. the ratio is always consistent. (ratio is whole number)

5. Atoms not destoryed nor created in chem change just rearranged

Law of definite proportions/constant composition

• #s of atoms of a given element always exist in the same ratio

Law of multiple proportions

• when two elements form more than one compound →will react with masses of the other element in a ratio of small, whole numbers

2.2 Evolution of Atomic Theory

electron - negatively charged subatomic particle

alpha particles - 2 protons + 2 neutrons

Erenest Rutherford findings

• atoms have a large amount of empty space

• atoms have nucleus. small (relatively heavy) positive charge at their center.

• proton - positively charged subatomic particle @ nucleus

isotopes - atoms @ same element that differ in mass

What did James Chadwick find?

• neutrons - uncharged subatomic particles mass roughly the same as a proton

• → neutrons explain isotopes bc they change the mass but not the charges

2.3 Atomic Structure & Symbolism

what do we use to measure atoms?

• unified atomic mass unit (u) = dalton (Da)

• fundamental unit of charge (e)

atomic number (Z)

• # of protons in the nucleus @ atom

• → defining trait. determines atom’s identity

atomic number shows → mass # (A)

• total # of protons & neutrons

ion - when subatomic particles are not equal

anion - gains 1 or more electrons → negative charge

cations - losses 1 or more electrons → positive charge

Chemical symbols - abbreviation for element/atom of element

• microscopic → Hg one atom of mercury

• macroscopic →Hg conatiner of mercury

atomic mass - it’s amu. the amount of protons & neutrons in an atom

not a single atom weighs that much it is the average of all the atoms

2.4 Chemical Formulas

molecular formula - rep @ molecule uses chemical symbols to indicate the types of atoms, followed by subscripts to show the number of atoms of each type in the molecule.

structural formula - same as molecular formula EXCEPT shows how atoms are connected @ molecule

What’s the rule for subscripts & for # before the chem symbol?

• before the chem symbol then it is two separate atoms

• if subscript it is connected

empirical formula - simplest whole # ratio of atoms (or ions) in a compound

isomers - compounds with the same chemical formula but different molecular structure

• structural isomers

• spatial isomers - relative orientations of the atoms in space can be different.

2.5 The Periodic Table

periodic law - properties of elements are in periodic functions of their atomic #

Overarching classes of elements:

• metals - shiny, malleable, good conductors of heat and electricity

• nonmetals - dull, poor conductors of heat and electricity

• metalloids - conduct heat and electricity moderately well (between metals & nonmetals)

group 1 - representative/main group elements

group 2 - representative/main group elements. alkali earth metals

group 3 - transition metals

group 4 - transition metals

group 5 - transition metals

group 6 - transition metals

group 7 - transition metals

group 8 - transition metals

group 9 - transition metals

group 10 - transition metals

group 11 - transition metals

group 12 - transition metals

group 13 - representative/main group elements

group 14 - representative/main group elements

group 15 - representative/main group elements. pnictogens

group 16 - representative/main group elements. chalcogens

group 17 - representative/main group elements. halogens.

group 18 - representative/main group elements. noble gases/inert gases

inner transition metals in the two rows at the bottom of the table (the top-row elements are called lanthanides and the bottom-row elements are actinides

2.6 Ions & Molecular Compunds

when electrons transferred & ions formed → ionic bonds

electrons shared → covalent bonds

ionic compound

• contains ions & held together by ionic bonds

• solids, melt at high temps, boils at higher temps

• does not conduct electricity

• formula is ratio of ions → positive & negative charges equal

why is the formula important? * do practice problems of this & predicting bonds

    EX: Al³+ and O²-

         $Al^{3+}=O^{2-}$

           ionic compounds MUST BE electrically neutral so these are equal… with 6               charges on each side

          $\left(2\right)Al^{3+}=\left(3\right)O^{2-}$

           final formula: $Al_2O_3$

molecular compounds (aka covalent compounds)

• often gases

• low boiling & low melting solids (there are exceptions though)

2.7 Chemical Nomenclature

nomenclature - collection of rules about naming things

binary compounds - only consisting of two elements

ionic compounds

compounds containing metal ion w/ variable charge

• named cation then anion

• metal ion’s charge is shown in roman numerals

EX: iron (II) chloride, $FeCl_2$ the iron has a charge of 2+

ionic hydrates

hydrates - ionic compounds that contain water molecules as integral components of their crystals

• # of water molecules + suffix hydrate

Molecular (Covalent) Compounds

• names indicate the ratio

  

Compounds Composed of Two Elements

• 1st name of the more metallic element (the one farther to the left and/or bottom of the periodic table)

• 2nd nonmetallatic element with “-ide” ending

Binary Acids

what is a binary acid? →compound comprised of hydrogen & one other nonmetallic element)

Naming:

• hydrogen →prefix “hydro-”

• nonmetallic element suffix “-ic”

• Add acid at the end!

EX: Hydrochloric acid, HCl

Oxyacids

What is an oxyacid? → compounds that contain hydrogen, oxygen & one other element

• hydrogen, oxygen & one other element

• naming: no “hydrogen”, root of anion,

• naming: –ate →–ic, or –ite → –ous

EX: $HNO_2$ , nitrous acid