CHEM 120: Midterm-Review
1. The Scientific Method
Hypothesis : a testable educated guess
Experiments: how we test hypotheses
o Variable: idea to be tested (only one)
o Control: something the variable is tested against; what your testing
against
o Experimental protocol: how do you do the test?
o Results: data generated comparing variable to controls. Includes statistics
to show results are meaningful
o Conclusion: interpretation of results
2. Density
Density (d), of a substance is the quantity of mass (m), per unit of volume (v)
D = m/d; m = d X V; V = m/d
3. Metric; Measurement conversions (metric to metric only)
1 kilometer (km) = 1000 meters (m)
1 meter (m) = 100 centimeters (cm)
1 centimeter (cm) = 10 millimeters (mm)
1 millimeter (mm) = 1000 micrometers (um)
1 kilogram (kg) = 1000 grams (g)
1 gram (g) = 1000 milligrams (mg)
1 milligram (mg) = 1000 micrograms (ug)
1 liter (L) = 1000 milliliters (mL)
1 milliliter (mL) = 1000 microliters (uL)
1 milliliter (ml) = 1 cubic centimeter (cm3)
4. Avagado’s Number, mole
A mole (mol) = 6.02 X 1023
5. Molar Mass
Equal to the atomic mass but expressed as unit grams per mole (g/mol)
, 6. Atomic Number, atomic mass, isotopes, number of protons, electron, neutrons
Atomic mass is expressed as amu ; is the weighted average
Atomic Number is the number of protons in the nucleus of an atom of
any element
Isotopes have the same atomic number but different mass
numbers(same number protons different number protons)
Electrons are negatively charged particles in the nucleus
Protons are positively charged particles in the nucleus
Neutrons are neutral, have no electrical charge
Atomic number = the number of protons
Atomic number – (minus) atomic mass = neutrons
7. Calculating Bonds
Subtract the smaller EN value from the larger EN value
o 0 – 0.4 = nonpolar covalent
o > (greater than) 0.4 – 1.7 = polar covalent
o > ( greater than) 1.7 = ionic bond
Ionic bonds is a bond that forms when electrons is being transferred from one
form to another form. which results in positive & negative ions.
Cations – are positively charged ions; think of the “t” in cat as a +
Anion – are negatively charged ions
Covalent bond – a bond formed when atoms share electrons
Nonpolar covalent bonds – when the EN is very similar between 2 atoms
Polar covalent – when the EN is different between 2 atoms
8. Naming element from electron orbital configuration
Hydrogen = 1s1
Helium = 1s2
Lithium = 1s22s1
Beryllium = 1s22s2
Boron = 1s22s22p1
Carbon = 1s22s22p2
Nitrogen = 1s22s22p3
Oxygen = 1s22s22p4
Fluorine = 1s22s22p5
Neon = 1s22s22p6
Sodium = 1s22s22p63s1
Magnesium = 1s22s22p63s2
Aluminum = 1s22s22p63s23p1
1. The Scientific Method
Hypothesis : a testable educated guess
Experiments: how we test hypotheses
o Variable: idea to be tested (only one)
o Control: something the variable is tested against; what your testing
against
o Experimental protocol: how do you do the test?
o Results: data generated comparing variable to controls. Includes statistics
to show results are meaningful
o Conclusion: interpretation of results
2. Density
Density (d), of a substance is the quantity of mass (m), per unit of volume (v)
D = m/d; m = d X V; V = m/d
3. Metric; Measurement conversions (metric to metric only)
1 kilometer (km) = 1000 meters (m)
1 meter (m) = 100 centimeters (cm)
1 centimeter (cm) = 10 millimeters (mm)
1 millimeter (mm) = 1000 micrometers (um)
1 kilogram (kg) = 1000 grams (g)
1 gram (g) = 1000 milligrams (mg)
1 milligram (mg) = 1000 micrograms (ug)
1 liter (L) = 1000 milliliters (mL)
1 milliliter (mL) = 1000 microliters (uL)
1 milliliter (ml) = 1 cubic centimeter (cm3)
4. Avagado’s Number, mole
A mole (mol) = 6.02 X 1023
5. Molar Mass
Equal to the atomic mass but expressed as unit grams per mole (g/mol)
, 6. Atomic Number, atomic mass, isotopes, number of protons, electron, neutrons
Atomic mass is expressed as amu ; is the weighted average
Atomic Number is the number of protons in the nucleus of an atom of
any element
Isotopes have the same atomic number but different mass
numbers(same number protons different number protons)
Electrons are negatively charged particles in the nucleus
Protons are positively charged particles in the nucleus
Neutrons are neutral, have no electrical charge
Atomic number = the number of protons
Atomic number – (minus) atomic mass = neutrons
7. Calculating Bonds
Subtract the smaller EN value from the larger EN value
o 0 – 0.4 = nonpolar covalent
o > (greater than) 0.4 – 1.7 = polar covalent
o > ( greater than) 1.7 = ionic bond
Ionic bonds is a bond that forms when electrons is being transferred from one
form to another form. which results in positive & negative ions.
Cations – are positively charged ions; think of the “t” in cat as a +
Anion – are negatively charged ions
Covalent bond – a bond formed when atoms share electrons
Nonpolar covalent bonds – when the EN is very similar between 2 atoms
Polar covalent – when the EN is different between 2 atoms
8. Naming element from electron orbital configuration
Hydrogen = 1s1
Helium = 1s2
Lithium = 1s22s1
Beryllium = 1s22s2
Boron = 1s22s22p1
Carbon = 1s22s22p2
Nitrogen = 1s22s22p3
Oxygen = 1s22s22p4
Fluorine = 1s22s22p5
Neon = 1s22s22p6
Sodium = 1s22s22p63s1
Magnesium = 1s22s22p63s2
Aluminum = 1s22s22p63s23p1
