MCAT General Chemistry Review 1

Avogadro’s Number

6.022×10^23 am = 1 gram

;

moles =
moles = grams/atomic or molecular weight
Metals

Left side of metalloids

Large atoms that tend to lose electrons to form cations.

Nonmetals

Right side of metalloids.

Diverse appearances and chemical behaviors.

Lower melting points than metals.

Form negative ions.

Form covalent oxides.

Transition metals
D block metals.
Effective nuclear charge (Z_eff)
Amount of charge felt by the second electron by the nucleus.
Atomic Radius
Increases Down to the Left.
Ionization Energy

Energy necessary to detach an electron from the nucleus.

;Increases Up and to the Right

Second Inonization Energy
Energy for the removal of a second electron.
Electronegativity

Tendancy of an atom to attract an electron in a bond that it shares with another atom.

Increases to the Right;and Up.

Electron Affinity

Willingness of an atom to accept an additional electron.;

The energy released when an electron is added to a gaseous atom.

Increases to the Right;and Up.

Metallic Character
Increases to the Left and Down.
Covalent Bond

Two molecules share two electrons.

The negatively charged electrons are pulled toward both postively charged nuclei by electrostatic forces.

Empirical Formula
The reduced ratio of atoms in a compounds.
Molecular Formula
The exact number of elemental atoms in a compound.
Ionic Compounds

Bond formed by a cation and anion.

Metal and Nonmetal.

Metathesis

Double Displacement Reaction;

AB+CD–>AD+CB

Ionic Crystals
Oppositely charged ions held together by electrostatic forces. (Salts)
Network Covalent Crystals
Consist of an infinite network of atoms held together by polar and nonpolar bonds. (Diamond, crystal SiO2)
Quatum Numbers

Principal Number, n

Azimuthal Number, l

Magnetic Number, m

Electron Spin Number, m_s

Principal Quatum Number

n

designates the shell level

 

Azimuthal Quatum Number

l

designates the subshell

These are the orbital shapes

l=n-1

s=0, p=1, etc

Magnetic Quantum Number

m_l

Designates the precise orbital of a given subshell.

l to l


Electron Spin Number

m_s

-1/2 or 1/2

Pauli Exclusions Principle
No two electrons in the same atom can have the same four Quantum numbers.
Heisenberg Uncertainty Principle
There is an inherent uncertainty in the product of the position of a particle and its momentum.
Aufbau Principle
Electrons add to the lowest energy state first.
Hund’s Rule
Electrons fill the orbital of a subshell in order.
Planck’s Quantum Theory

Electromagnetic energy is quantitized.

E_photon = hf

(h = Planck’s constant, 6.6×10^-34 J)

Planck’s constant, h 
h=6.6×10^-34 J
Energy of a single photon
E_photon = hf
Wave characteristic equation
λ=h/mv
Intermolecular Bonding
All intermolecular bonding is via electrostatic forces.
Van der Waals interactions

Rely on temporary induced dipoles.

Weaker than dipole-dipole interaction.

Dipole-Dipole Interaction

Stronger than Van der Waals interactions.

May be due to permanent dipoles.

Electron Affinity change with atomic number
Increases (becomes more exothermic) to the right and up.
Molarity
Molarity = Density/MW

= moles/volume

The molarity of gases are equivalent at the same temperature and pressure.
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