Basic chemistry

• Protons and neutrons are held together by nuclear force
• Binding energy - energy that would be required to break nucleus into individual protons and neutrons
• Nucleons consist of neutrons and protons
• Z stands for atomic number, A stands for mass number and C stands for charge

  
• Z is equal to number of protons
• A is equal to number of protons + neutrons
• Isotopes are 2 or more atoms of the same element that contain different number of neutrons
• C is equal to protons - electrons
• In the neutral atom, protons and electrons are equal
• Cation is positively charged because it has more protons
• Anion is negatively charged because it has more electrons
• Protium is the most stable H, 2H is deuterium and 3H is tritium
• Electrons in the atom experience both repulsive forces between each other and attractive force to nucleus
• Cation is smaller than neutral atom, and anion is larger than neutral atom
• Metals tend to lose electrons and become cations
• Nonmetals tend to gain electrons and form anions
• Nonmetals have lower melting points than metals
• Group 1 are called alkali metals and they are soft solids, low densities, low melting points
• Group 2 are called alkaline metals and are harder, more dense and melt at higher temperatures than group 1
• Heavier alkaline metals are more reactive than lighter ones
• 1e equals 1.6 x 10 in -19 coulombs
• Degenerate means having same energy
• Para in chemistry means spread out
• Think of nonmentals like of candles: they are poor conductors of heat & electricity, non-malleable and brittle
• Metals are ductile (means easily stretched), malleable, conductive and luster (which means shine)
• Metallic bonds exhibit electron-sea model which is like electron socialism: they share all electrons
• Symmetric molecules with covalent bond are nonpolar
• Intramolecular bonds are ionic, metallic, covalent
• Intermolecular bonds are dispersion forces, dipole-dipole, hydrogen
• Dipole-dipole bond happens when polar molecules are attracted to each other, their negative dipoles attracted to positive dipole of another molecule
• Hydrogen bond needs 2 requirements: H atom as an electron pair acceptor, and F, O or N atom as an electron pair donor
• London dispersion forces are caused by formation of instantaneous dipole in the electron cloud of a given molecule: randomly electrons are more on one side, so it forces electrons of another molecule to move away, polarizing it
• Among intermolecular forces, hydrogen bond is the strongest
• Intramolecular forces are stronger than intermolecular
• London dispersion forces are higher in heavier more polarizable molecules
• The greater the number of intermolecular forces, the greater is the viscocity, boiliing and melting of that molecules
• When bonds are formed energy is released, because atoms are in their lowest energy state together
• Bond dissociation energy is the energy required to break the bond
• Hydrogen bond has H that is covalently bound to F, O or N and then hydrogen bonded to another molecule’s F, O or N
• Induced dipole occurs in a nonpolar molecule or bond by a polar molecule, ion or electric field