Download Exam Review/SLO 1 Topics Mixtures Have two or more different

Exam Review/SLO 1 Topics
Mixtures
Have two or more different particles
Heterogeneous
Homogeneous
Solutions, alloys
Pure Substances
Have only one type of particle
Elements
Compounds
Have different properties than the elements from which they are made
Extensive properties
Depend on how much matter is present (mass, volume, weight, etc.)
Intensive properties
Depend on type of matter present (density, melting point, boiling point, etc.)
Do not depend on how much matter is present
Physical Properties
Properties which can be observed without a change in identity (chemical make-up)
Examples: boiling point, melting point, density
Density = mass / volume (although an intensive property, can vary with temperature)
Chemical Properties
Describe the ways that elements and compounds react to form new substances
For an element, depends upon electron configuration of the element
Basic atomic structure
Nucleus
Protons & neutrons
Small, positively charged
Electrons
Negatively charged
Occupy electron cloud surrounding nucleus
Atomic Number = number of protons in nucleus
Different elements defined by different atomic numbers
Mass Number = sum of protons + neutrons
Isotopes of an element
Have the same atomic number but different mass numbers
Have different numbers of neutrons
Examples:
# neutrons = mass number – atomic number
Atomic masses of elements are weighted averages of the masses of isotopes
Average atomic mass is closest to the most abundant isotope
David Scott, Rev. 2017
Chemistry
Dalton’s Atomic Theory
First scientific theory of atom
Atoms are indivisible
Law of definite proportions: atoms combine to form acompound in a constant
proportion by mass
JJ Thomson
Discovered electron, charge/mass ratio of electron
Cathode ray tube experiment
Plum pudding model
Rutherford
Gold foil experiment
Discovered nucleus
Most alpha particles (+ charged) went through foil, some deflected at large angles, a few
bounced off
Conclusison: nucleus is very small, dense, positively charged
Bohr Model of Atom
Electrons occupy only allowed energy levels
Electrons absorb quanta of energy and release photons of light as they change energy levels
Explains atomic spectra
Quantum Model of Atom
Current model
Atoms consist of a small dense positive nucleus surrounded by an electron cloud
Electron cloud is described with energy levels and atomic orbitals
Periodic Table
Groups & Periods
Arranged by increasing atomic number
Metals, metalloids, non-metals
Location on PT
Basic properties
Energy levels & orbital blocks (s, p, d, f)
Group names
Elements within a group have similar chemical properties because their ending e-config is the
same (i.e., same number of valence electrons in their outer shell)
Periodic Trends
Electronegativity: Fluorine is greatest; increases from L to R; decreases from top to
bottom
Ionization Energy: Energy needed to remove an electron from an atom
Alkalai metals have lowest IE
David Scott, Rev. 2017
Chemistry
Ions
Are atoms which have gained or lost electrons
Losing electrons  positive ion (cation)
Gaining electrons  negative ion (anion)
Octet rule
Determine # valence electrons using periodic table
Representative elements gain, lose, or share electrons to achieve an octet (noble gas e-config)
Use to predict ionic charges, formation of ions, formula units, molecular formulas
Electron configurations
Groups of the periodic table reflects atomic orbitals, s, p, d, and f blocks
Periods (rows) of the periodic table reflect energy levels
Formation of ionic compounds
Molar Mass
The mass of one mole of a compound
Calculate by adding atomic masses of atoms in the formula
Example, CaCl2 = [40 + 2(35.5)] = 111 g/mol
Mole Calculations
Moles = grams / molar mass
One mole contains 6.02 x 1023 particles
# atoms = mass / molar mass x Avogadro’s number
Percent Mass Calculations
Is percentage of an element in a compound by mass
%X = mass of X in compound / molar mass
Example: % Cl in CaCl2 = mass Cl/mol mass = [2(35.5)]/111 = 64%
Molecular & Empirical Formulas
Empirical formula is the simplest whole number ratio of elements in a compound
Molecular formula is a whole number multiple (n) of the empirical formula
Examples: Empirical CH2O
Molecular C6H12O6
Ionic Compounds
Contain ionic bonds
Composed of cations and anions in a ratio that results in electrical neutrality
Example: Ca2+ + 2 Cl-  CaCl2
Consist of metals and nonmetals
Molecular Compounds
Contain covalent bonds
Consist of nonmetals only
Chemical Bonds
Ionic: cations & anions joined by electrostatic force of attraction
Metallic: cations attracted to core electrons of other atoms; electron sea model
Covalent: share pair(s) of electrons; contained in molecular compounds
Lewis Structures
Elements & Compounds
David Scott, Rev. 2017
Chemistry