Understanding Lewis Structures, Resonance, and Hybridization
Lewis Structures of Bonding Electrons
Lewis Structures represent bonding electrons, non-bonding electrons (lone pairs), and the dipole moment. The dipole moment is the product of the electric charge and the length of the bond. Elements with higher electronegativity attract electrons more strongly.
Writing Lewis Structures
- Write the basic structure of the compound, joining the atoms together. The less electronegative atom tends to go in the center.
- Count the total number of valence electrons present.
Barometers, Natural Gas, and LPG: Properties and Uses
What is a Barometer, How Does it Work, and What is its Origin?
The barometer, invented by Evangelista Torricelli, measures the force per unit area exerted by the weight of the atmosphere, known as atmospheric pressure. Torricelli’s barometer used a mercury-filled tube approximately 76 inches high, balanced by atmospheric pressure. His studies indicated that air exerts a pressure of 1,033 grams per square centimeter (1.033 g/cm2).
What are the Differences Between Mercury and Aneroid Barometers?
A mercury
Read MoreChemical Elements and the Periodic Table: Properties and Structure
Metals and Non-Metals
Since antiquity, items such as gold, silver, etc. have been discovered over time. Up to now, more than 100 have been identified. A first classification of items, focusing on appearance and physical properties, allows for 2 groups: metals and non-metals.
Metals and Non-Metals
To distinguish one from the other, we will name characteristics that make them different:
Metallic Elements
- Have a characteristic brightness.
- Are opaque and good conductors of heat and electricity.
- Are usually
Thermodynamics Problems and Solutions: Ideal Gas Law
Ideal Gas Law and Thermodynamics Problems
Problem 1
An ideal gas occupies a volume of 100 cm3 at 20°C and a pressure of 100 Pa. Determine the number of moles of gas in the vessel.
1 Pa * 1 m3 = 1 Joule
PV = nRT
100 Pa * 10 * 10-7m3 = n
8.31 * 293
n = 4.11 * 10-6
Problem 2
Calculate the volume occupied by one mole of gas under normal conditions.
PV = nRT
1 atm * V = 1 mol * 0.082 * 273
V = 22.4 L
Problem 3
Helium is introduced into a mobile container. The initial pressure, volume, and temperature of the gas are
Read MoreAcid-Base Titration and Salt Hydrolysis in Chemistry
Acid-Base Titration
In both industrial processes and in the laboratory, it is very common to determine the amount of acid or base in a sample. Titration, specifically acid-base titration, is a method of chemical analysis used to determine the unknown concentration of an acidic or basic solution. This is achieved by using a standard solution, which is a basic or acidic solution of known concentration.
The experimental procedure involves placing a known volume of the solution to be analyzed in a conical
Read MoreChemical Properties and Reactions: Elements, Compounds, and Laws
Periodic Properties of Elements
Atomic Radius
The atomic radius is the distance from the center of the nucleus to the area corresponding to the outermost level. Over a period, the radius decreases from left to right.
Ionization Energy
Ionization energy is the energy required to form an ion (cation); the energy that must be delivered to an isolated atom to remove an electron. The ionization increases from left to right, and in a group, it decreases from top to bottom.
Electronegativity
Electronegativity
Read More