Fundamental Concepts in General Chemistry: Atomic Theory, Periodic Table, and Chemical Formulas

Dalton's Atomic Theory and Laws of Chemistry

Dalton's Atomic Theory

Dalton's Atomic Theory laid the foundation for modern chemistry by describing the nature of atoms and their role in chemical reactions.

• All elements are made of atoms: Atoms are the smallest units of matter that retain the properties of an element.

• Atoms of the same element are identical: Atoms of a given element have identical properties, but differ from atoms of other elements.

• Atoms are not created nor destroyed in chemical reactions: Chemical reactions involve the rearrangement of atoms, not their creation or destruction.

• Compounds form when atoms of more than one element combine: Chemical compounds consist of atoms from different elements bonded together in fixed ratios.

Law of Conservation of Mass

The Law of Conservation of Mass states that mass is neither created nor destroyed in a chemical reaction.

• Key Point: The total mass of reactants equals the total mass of products.

• Example: Burning of hydrogen in oxygen produces water, but the total mass remains constant.

Law of Multiple Proportions

This law explains how elements can combine in different ratios to form different compounds.

• Key Point: The same two elements can form more than one compound, with mass ratios of one element to another being simple whole numbers.

• Example: Carbon and oxygen form both CO and CO2.

Structure of the Atom

Subatomic Particles

Atoms are composed of three main subatomic particles, each with distinct properties and locations.

• Protons: Positive charge, located inside the nucleus.

• Neutrons: Neutral charge, located inside the nucleus.

• Electrons: Negative charge, located outside the nucleus in electron clouds.

Isotopes

Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons.

• Key Point: Isotopes have identical chemical properties but different atomic masses.

• Example: Carbon-12 and Carbon-14.

Atomic Weight Calculation

The atomic weight of an element is the weighted average of the masses of its isotopes.

• Formula:

$\text{Atomic Weight} = \sum (\text{Isotope Mass} \times \text{Fractional Abundance})$

The Periodic Table

Organization of the Periodic Table

The periodic table arranges elements by increasing atomic number and groups elements with similar properties together.

• Rows: Called periods.

• Columns: Called families or groups.

Classification of Elements

Elements are classified as metals, nonmetals, or metalloids based on their properties and position on the table.

• Metals: Located on the left of the "staircase"; typically shiny, malleable, and good conductors.

• Nonmetals: Located on the right; often dull, brittle, and poor conductors.

• Metalloids: Have properties intermediate between metals and nonmetals.

Diatomic Elements

Certain elements exist naturally as diatomic molecules, meaning two atoms are bonded together.

• Key Diatomic Elements: Hydrogen, nitrogen, oxygen, fluorine, chlorine, bromine, iodine.

• Example: O2 (oxygen gas).

Chemical Compounds and Formulas

Molecular Compounds

Molecular compounds are formed when two or more nonmetals bond through covalent sharing of electrons.

• Key Point: Covalent bonds involve electron sharing between atoms.

• Example: H2O (water).

Molecular vs. Empirical Formulas

Chemical formulas can be expressed as molecular or empirical formulas.

• Molecular Formula: Shows the exact number of atoms of each element in a molecule.

• Empirical Formula: Shows the simplest whole-number ratio of atoms in a compound.

• Example: Glucose: Molecular formula C6H12O6, Empirical formula CH2O.

Ions and Ionic Compounds

Polyatomic Ions

Polyatomic ions are charged species composed of two or more atoms covalently bonded, acting as a single unit.

• Key Point: Polyatomic ions have a net electric charge.

• Example: Sulfate (SO42-), Nitrate (NO3-).

Predicting Ionic Charges

The charge of an ion can often be predicted based on its group in the periodic table.

Group	Typical Ion Charge
Group 1 (e.g., Na, Li)	+1
Group 2 (e.g., Mg, Ca)	+2
Group 16 (e.g., O, S)	-2
Group 17 (e.g., Cl, Br)	-1

• Example: Sodium (Na) forms Na+, Oxygen (O) forms O2-, Chlorine (Cl) forms Cl-.

Naming and Writing Chemical Formulas

Common Compounds and Their Formulas

Understanding the names and formulas of common compounds is essential for chemical communication.

Name	Formula
Calcium Bicarbonate	Ca(HCO3)2
Sodium Hydroxide	NaOH
Sulfuric Acid	H2SO4
Dinitrogen Hexoxide	N2O6

• Example: Sulfuric acid is a strong acid commonly used in industry.

Additional info:

• Some context and explanations have been expanded for clarity and completeness.

• Tables have been inferred and formatted for clarity.