Moles to Volume Conversion

• a specific pressure and temperature one mole of any gas occupies the same volume.
• At 0˚c and 101.3kPa 1 mol = 22.4L
• this temperature and pressure is called STP
• 22.4L/mol is the molar volume at STP

ex. How many liters will 2.5 mol of H2 occupy at STP?

2.5 mol x 22.4L/mol= 56 L

Mole Conversions

Converting between moles and mass

• To convert between moles and mass we use molar mass as the conversion factor
• Be sure to cancel the appropriate units

Ex. How many grams is there in 1.5 mol of 02?

1.5 mol 02 x 32 g/ 1 mol = 48 g O2

Molar Mass

• The mass (in grams) in one mole of a substance is called the molar mass.
• It can be determined from the atomic mass on the periodic table.
• Measure in g/mol

Molar Mass of Compounds

• To determine the molar mass of a 'compound' add the mass of all the atoms together.

Avogadro's Number

• atoms and molecules are extremely small
• macroscopic objects contains too many to count or weigh individually
• Amedo Avogrado proposed that the number of atoms is 12.00000 g of carbon be equal to a constant. ( This is equal to 1 mol of carbon)
• This value is now called Avogadro's number and forms the basis of all quantitive chemistry.
• Avogadro's number 6.02x 10^23
• 1 mol = 6.02x10^23
• One mole is simply refer to 1 multiple of things
• One mole represents a huge number of particles

 

 

 EX.

a sample of carbon contains 2.47x10^25. How many carbon is this?

2.47x10^25 x 1 mol/6.02x10^23 atoms = 41.0 mol

0.57 mol x 6.02x10^23 FU/1mol = 3.43x10^23

Electronic Structure

Drawing Electron Dot Diagrams

• The nucleus is represented by the atomic symbol
• For individual elements determine the number of valence electrons.
• Elements are represented by dots around the symbol
• Four orbitals(one of each side of the nucleus) each holdng a maximum of 2 e-

• Each orbital gets 1 e- before they power it up

Lewis Diagrams for Compounds and Ions

• in covalent compounds electrons are shared
• determine the number of valence e- for each atom in the molecule.
• place atoms so that the e- are shared to fill each orbital

 Double & Triple Bonds

• somtimes the only covalent compounds can fill at their valence levels is if they share more than 1 electron.

Ionic Compounds

• In ionic compounds electrons transfer from one element to another
• determine the number of valence e- on the cation. Move these to the anion.
• Draw the [ ] around the metal and non-metal.
• write the charges outside the brackets.

Trends On a Periodic Table

• Elements close to each other on the periodic table display similar characteristics.
• There are 7 important periodic trends
• Reactivity- metals and non metals show different trends
• The most reactive metal is Francium and the most reactive non-metal metal is Flourine.
• Ion charge- elements ion charges depends on their group melting point.
• elements in the center have the highest melting point.
• noble gases have the lowest melting point
• melting point increases from left to right until the middle of the table
• Atomic radius
• decreases to the up and the right
• helium has the smallest atomic radius
• Ionization energy- energy needed to completely move an electron from an atom
• increases going up and to the right
• all noble gases have high ionization energy
• helium is highest
• francium is lowest
• Electronegativity
• refers to how much atoms want to gain electrons

Isotopes and Atoms

- Atomic number = number  of protons


Atomic Mass - Atomic Number = # Neutrons
    (p+n)         -          (p)            =       (n)

*Most radiation comes from isotopes

Isotopes - same atomic number but different mass
Not all atoms of the same element are identical

MASS SPECTROMETERS

• A device known as mass spectrometer can be used to determine the relative abundance and the mass of the isotopes of elements