Chapter 5 - Molecules and Compunds Flashcards
mixture vs. compound
a compound is composed of a fixed ratio of elements. a mixture can have an indefinite proportion.
Law of Constant Composition
all samples of a given compound have the same proportion of their constituent elements
mass ratio= (mass of element 1)/(mass of element 2)
Mass Ratio
-a compound composed of 2 elements (A + B) has a ratio of (mass A)/(mass B)
Order of listing nonmetals in a chemical formula
C,P,N,H,S,I,Br,Cl,O,F
Chemical Formula
- indicates the elements present in the compound and the relative number of atoms of each element
- the most metal like elements goes first
ex. H2O has 2 H and 1 O
Polyatomic Ion
- when more chemical formulas contain groups of atoms that act as a unit.
- set in parenthesis in the formula
- capable of having their own charge
ex. NO3- is a polyatomic ion in Mg(NO3)2
- there are 2 No3- for every Mg
3 types of chem formulas
1 empirical formula
2 molecular formula
3 structural formula
Empirical Formula
- simplest whole-number ratio of atoms of each element in a compound
Molecular Formula
- actual number of atoms of each element in a molecule of the compound
ex. molecular form of hydrogen peroxide is H2O2
empirical form is HO (bc that’s the simplest ratio)
mole form of water is H2O and empirical form is also H2O bc that’s the smallest ratio
Structural Formula
- uses lines to represent chemical bonds and shows how the atoms in a molecule are connected to each other
ex) hydrogen peroxide is H-O-O-H
Molecular Models
3d representation of molecules to represent compounds
Ball-and-Stick Models
balls represent atoms and sticks represent bonds
Space-filling Models
atoms fill the space b/w each other to more closely represent our best idea of how molecules might appear if we scale it to a visible size
Pure Substances
are either Elements or Compounds
- Elements are either atomic or molecular
- Compounds are either molecular or ionic
Atomic Elements
-have single atoms as their basic units
Molecular Elements
- do not normally exist in nature with single atoms as their basic units
- instead their exist as diatomic molecules as their basic units
Diatomic Molecules
2 atoms of the same element bonded together
ex. O2, Cl2
Molecular Compounds
- composed of two or more nonmetals
- basic units are molecules composed of constituent atoms
Ionic Compound
- composed of 1 or more CATIONS + 1 or more ANIONS
- metals (cations) + nonmetals (anions)
- attracted to each other bc of opposite charge
- basic unit are Formula Units
- always contain pos + neg ions; sum must always be charge-neutral
Formula Units
- smallest electrically neutral collection of ions
- differ from molecules in that they don’t exist as discrete entities; instead they are make up a larger 3-d array
ex) ionic compound is ;:;:;:;:;;;;:;;;:;:;;:;;
a mole compound is ;:;: :;;:; :;;:; :;;:;
How to write formulas for Ionic Compounds w/ Monoatomic Ions
1 write the symbol for metal w/ charge and nonmetal w/ charge (Al3+ O2-)
2 use the charge of the metal ion for subscript of the nonmetal and vice versa (Al2O3)
3 if possible, reduce the subscript (Al2O3 is the smallest already)
4 check if it has a neutral charge
(cations: 2(3+)=6+
anions: 3(2-)=6-)
How to write formulas for Ionic Compounds w/ Polyatomic Ions
1 write the symbol for metal w/ charge and polyatomic ion w/ charge (Ca2 + NO3-)
2 use the charge of the metal ion for subscript of the polyatomic ion and vice versa [Ca1(NO3)2}
3 if possible, reduce the subscript [Ca(NO3)2]
4 check if it has a neutral charge
(cation: 2+
anion: 2(1-)=2-)
Ionic Compound Type I
contains metal w/invariant charge - one that does not vary from one compound to another
ex) Sodium has 1+ charge in any compound it is in
Ionic Compound Type II
contains a metal with a charge that can differ in different compounds
- any metal except Ag, Zn, Al, Sc, 1A, 2A
ex) Cu+, Cu2+
naming Ionic Compound Type I
[name of metal/cation] + [base name of nonmetal/anion +IDE]
ex)NaCl - sodium chloride
naming Ionic Compound Type II
[name of metal/cation] +[(charge in roman numeral)] + [base name of nonmetal/anion +IDE]
ex) PbCl4 - lead(IV) chloride
naming Ionic Compound w Polyatomic Ion
[name of metal w/roman num if TypeII] + [name of polyatomic ion]
ex) Fe(OH)2 - iron(II) hydroxide
Oxyanions
anions containing O
ex) NO3- nitrate, NO2- nitrite
Naming Molecular Compounds
[prefix][name of 1st element][prefix][name of 2nd element]
ex) N2O is dinitrogen monoxide
element prefixes
1 mono 2 di 3 tri 4 tetra 5 penta 6 hexa 7 hepta 8 octa 9 nona 10 deca
***mono is usually dropped if its for the first element
Acids
molecular compounds that produce H+ ions when dissolved in water
- composed of H which is usually the first in their formula
- sour taste and able to dissolve metals
Binary Acids
contains only Hydrogen and nonmental
Oxyacids
acids that contains oxyanions
-has hydrogen, nonmetal, + oxygen
2 types of acids
1 binary acids
2 oxyacids
naming Binary Acids
[hydro][base name of nonmetal + IC] [acid]
ex. HCl is hydrochloric acid
naming Oxyacids
if oxyanion ends w -ATE:
[base name of axyanion-IC] [acid]
if oxyanion ends with -ITE:
[base name of oxyanion -OUS] [acid]
ex. H2SO3 has a sulfite. SULFUROUS ACID
3 types of nomenclature compounds
1 Ionic metal+nonmetal [type I + type II]
2 Molecular nonmetals only
3 Acid H+1 or more nonmetals[binary or oxyacids]
Formula Mass
- sum of the atomic masses of all the atoms in its chemical formula
form. mass= [#atoms of 1st element x atomic mass of 1st element] + [#atoms of 2nd element x atomic mass of 2nd element]
ex. H2O
form.mass=2(1.01amu) + 16.0amu
=18.02 amu
