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