Dalton's Atomic Theory

Atoms, Molecules, and Ions

• Chapter 2 explores atoms, molecules, and ions, the ubiquitous building blocks of matter.
• Chemistry always relates to these entities.

Atomic Theory

• The concept that matter is composed of small, indivisible particles called atoms dates back to the Greek philosopher Democritus.
• Dalton's atomic theory constitutes the basis of modern chemistry.
• Elements are composed of extremely small particles called atoms.
• All atoms of a given element are identical in size, mass, and chemical properties.
• Atoms of one element differ from the atoms of all other elements in their mass and chemical properties.
• Compounds form when atoms of more than one element combine; in any compound, the ratio of the number of atoms between any two of the elements present is either an integer or a simple fraction.
• A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction.
• Dalton's theory explains the law of definite proportions, stating that different samples of the same compound always contain the same elements in the same mass ratio.
• The theory also explains the law of multiple proportions; if two elements can combine to form more than one compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers.
• Dalton's postulates align with the law of conservation of mass, which notes that matter is neither created nor destroyed.

Structure of The Atom

• Dalton described atoms as extremely small and indivisible.
• Atoms possess an internal structure and are composed of subatomic particles.
• Discoveries led to the identification of three subatomic particles: electrons, protons, and neutrons.

The electron

• Scientists used the study of radiation to research atom structure.
• Cathode ray tubes played a part in discovering electrons.
• Cathode rays are streams of particles with a negative charge.
• English physicist J.J. Thomson determined the ratio of the electric charge to the mass of an electron.

Charge of an Electron

• American physicist R.A. Millikan determined the charge of an electron.
• Used to determine the mass of an electron.

Radiation Physics

• German physicist Wilhelm Röntgen observed that cathode rays that struck glass and metals emitted unknown rays.
• These rays would go through matter and would cause fluorescence in certain matter
• Since the cause of the rates was unknown Röntgen named them X-Rays.
• Marie Curie suggested the name radioactivity to describe spontaneous emission of particles or radiation.

The Proton and the Nucleus

• Thomson proposed that an atom could be visualized as a uniform sphere of positive charge in which electrons are embedded.
• Rutherford showed the structure of atoms with alpha particles.
• The majority of alpha particles go through the lamina without separating, or doing so in a light way.
• Rutherford explained this was because most atoms were empty space.
• Named the core Nucleus
• Named the Particles in the core Protons

The Neutron

• English physicist James Chadwick demonstrated the existence of neutrons
• Neutrons are electrically neutral particles with a mass slightly greater than that of protons found in the nucleus.

Atomic number, mass number and isotopes

• The number of protons and neutrons in an atom will identify the atom.
• In neutral atom the number of electrons is equal to the number of proteins.
• Atomic number determines the chemical identity of an element.
• Isotopes are atoms that have same atomic number, different mass number or the same number of proteins but different number of neutrons.
• Number of neutrons in an atom is equal to the difference between mass number and atomic number.

The periodic table

• Chemical elements are grouped based on similarities in physical and chemical characteristics.
• Metals, nonmetals, and metalloids, are the categories the elements can be.
• Metals are good conductors of heat and electricity, while nonmetals are bad conductors of heat and electricity.
• Metalloids have intermediate materials between metals and non metals.
• Elements can be referred to through numbers in the group in the periodic table.
• Group 1A elements are called alkali metals and Group 2A elements are called alkaline earth metals.
• Group 7A, F, CL, Br, I, At, is known as halogens and group Group 8A, He NE AR KR XE RN, are noble or Rare gases.

Molecules and Ions

• Most elements are composed of molecules or atom formed by atoms.

Molecule defined

• Aggregate with 2 atoms in a definitive colocation that remains union through a chemical force aka a chemical link.
• Can contain two or more atoms either of the same element or different element.
• Just as atoms are, molecules are electrically neutral.

Molecule Types

• A molecule of hydrogen is known as diatomic since it only contains two atoms.
• Elements that are naturally as diatomic are nitrogen and oxygen, fluorine, chlorine, bromine and iodine.
• Large amount of molecules contain more than two atoms they can be the same, such as ozone (O3) that's made of oxygen.
• Molecules with over then two elements are called polyatomic molecules such as water or ammonia.

About ions

• An ion is a atom or group of atoms that has a positive or negative net charge.
• The loss of one or more electrons in an atom makes it a Cation a ion with positive charge.
• Example Sodium atom + Electron results in Sodium cation Na+ .
• On the flip side a Anion is a ion whose negative charge is caused by an increase in number of electrons.
• The table salt, NaCl (sodium Chloride) is known as Anion since it contains Catrions and Anion.

The concept of monoatomic ions

• An atom can gain more then 1 electrons can receive a name of monoatomic ion.
• Metals tend to form catrions and nonmetals tend to produce onions unless otherwise.
• Combining two atoms or more can create a positive or negative chain.
• Anions that contain More then a atom will be known as polyatomic chains.

Chemical formulas

• Chemical formulas are used to express composition of molecules.
• Composition means the elements present.
• Chemical formulas can either be molecular or empirical.

Molecular formulas

• Indicates exact amount of Atoms of an element that exists in smallest piece of a substance.
• Numerical suffix indicates number of Atoms of the element that are present, like Water H2O were it has two molecules with one from an Oxygen molecule.
• Allotropes can be two or more types of chemical elements.

Molecular models

• Used for visualizing molecules, for example sphere models and bars, spatial model (Image).
• Spheres are made of plastics with perforated holes who have angles to have them attach atoms in similar way.
• Spatial are more exact since they indicate size of Atoms.

Empirical formulas (EF)

• Chemcial formulas that are the most straightforward.
• Sub indexes from all molecule formulas get lowered, the simplest way possible.
• Molecule representations that form empirical formula, but are truly represented in molecule formula.

Formulas of ionic compounds

• Normally similar to EF, because ionic compounds are not generated as discrete molecular units.
• NaCl sample will show some Nat and some Cl in the 3D.
• Cations must be numerically and structurally and anion to be numerically equal..

Compund rules

• Chemcials must not be shown using Chains or Aniom names.
• Elements with chain K plus Bro can generate KBro because charge is+1 plus -1 = zero so there's nor index.
• Zink Zn ion plus Yoduro to combine with ion Yoduro for Chain Yoduro Formula.
• Must multiply charge with -1 so formula will be ZNI2 Yoduro Zink
• AnAlt and An O-2 and next image for Subindexes chain formula + Anion.

Nomenclature of compounds

• When chemistry was small it was possible to memorize all names but it's not today.
• Some names were about phisycal origin, names got derivated by their apps

New naming system

• Over 12mm names.
• Lucky there doesn't has to be memorized the chemists came up with a clear way for substances.
• A rule system proposed is accepted globally makes communication easy between chemists.
• For studying names has to separate organic and inorganic compounds.

Organic vs Inorganic

• Organic compounds contain carbon commonly combined with elements like hydrogen, nitrogen and sulfur .Rest will be classified as Inorganic Compounds
• For convenience some CO or CO2 and or cYanuro or Carbonato or Bycarbonato will stay in Inorganic.
• Way Naming elements and simple rules.
• Naming can go in 4 categories including ionic chain, molecular groups bases and Hydrides

Ionic compounds

• Since we use cation is positive ions vs Anions that are negative with exception of ion amonio Nh plus 4.
• Rest of the Chains will come from atom names Elements
• Sodium name will derive on ion Sodium or chain Sodium etc.

Nomenclature UTO

• Is used often some anion atoms those will be represented on periodic array table. Chain UTOS are also used on some groups for example KCN to call cYanuro Potasio.
• So these as long as they follow same process are called TERNARY which they come in table form.
• Some metals like transition ones can form over one type of cation for chain type such as Iron, system makes sure we use suffix OSO and ISO for it chain.

Rules for chemical combinations

• Adjoining one 0 with acid ICO turns the acid UTO acid.
• Removing one 0 the acid name will switch to OSO.
• Rules to name OXIDAnions are some that go through chains