Periodic Table of Elements: History and Classification
The Periodic Table of Elements
The periodic table of elements is an organizational system that distributes various chemical elements based on specific criteria and characteristics. Its development is usually attributed to Dmitri Mendeleev, who ordered elements based on the periodic variation of chemical properties. Julius Lothar Meyer, working separately, developed a similar system based on the physical properties of atoms.
Discovery of Elements
While some elements such as gold (Au), silver (Ag), copper
Read MoreEssential Organic Chemistry: Reactions & Functional Groups
Carboxylic Acids: Properties & Reactions
- Oxidation: Primary alcohols or aldehydes
- Hydrolysis of Esters: Acidic or basic mechanisms
- Hell-Volhard-Zelinsky (HVZ) Reaction: α-halogenation via PBr3 and Br2
Key Characteristics of Carboxylic Acids
- Polar and acidic nature
- Form strong hydrogen bonds
- Undergo nucleophilic substitution reactions
Acid Derivatives: Synthesis & Reactivity
Includes acid chlorides, esters, amides, and anhydrides.
Synthesis Methods
- From acids using SOCl2 (for acid chlorides)
- From acids
Fundamental Concepts of Atomic Structure and Chemical Bonding
Subatomic Particles and Their Discoverers
-
Electron: Discovered by J.J. Thomson in 1897.
- Mass: Approximately 1/1837 of a proton’s mass.
- Mass (kg): 9.1 x 10-31 kg.
- Charge: -1 (relative charge).
-
Proton: Discovered by E. Rutherford in 1920.
- Mass (atomic mass unit, U): 1 U.
- Mass (kg): 1.7 x 10-27 kg.
-
Neutron: Discovered by J. Chadwick in 1932.
- Mass (atomic mass unit, U): 1 U.
- Mass (kg): 1.7 x 10-27 kg.
- Charge: 0 (neutral).
Models of the Atom
Rutherford’s Planetary Model
The planetary model of the atom was proposed
Read MoreElectrostatics Fundamentals: Charge, Conductors, and Coulomb’s Law
Electrostatics: The Study of Static Electric Charges
Electrostatics is the study of electric charges at rest. Objects can be electrified through three primary methods:
- Friction
- Contact
- Induction
Electric Charges (Q) and Atomic Structure
- Protons and electrons possess electric charges (positive and negative, respectively).
- Forces of attraction between these particles form atoms.
- Every atom consists of a positively charged nucleus surrounded by negatively charged electrons.
- Electrons across all atoms are identical,
Essential English: Verbs, Questions, Time, Numbers & More
The Verb “To Be” (Ser/Estar)
The verb “to be” is fundamental in English, equivalent to “ser” or “estar” in Spanish/Catalan.
Conjugation: Affirmative and Negative Forms
Affirmative | Negative | Contraction |
---|---|---|
I am | I am not | I’m not |
You are | You are not | You aren’t |
He/She/It is | He/She/It is not | He/She/It isn’t |
We are | We are not | We aren’t |
You are | You are not | You aren’t |
They are | They are not | They aren’t |
Essential Questions for Introductions
Here are some common questions to ask when getting to know someone:
- What is your name? (Spanish:
Essential Concepts in Chemistry, Biology & Materials Science
Surface Tension Measurement Techniques
Surface tension, a critical property of liquids, can be accurately measured using several established methods:
Measurement Methods
- Du Noüy Ring Method: Measures the force required to pull a ring out of a liquid.
- Wilhelmy Plate Method: Measures the force exerted on a plate partially submerged in a liquid.
- Drop Weight Method: Measures the weight of drops falling from a capillary.
- Pendant Drop Method: Analyzes the shape of a pendant drop to determine surface tension.