Chp 3 of Chem
First Atomistic Theory:
440 BC: Leucippus of Miletus first proposed that matter consists of tiny, discrete, indivisible, invisible particles called atoms, a theory further developed by his student Democritus of Abdera, but Aristotle’s belief in continuous matter was commonly accepted until the 17th century.
Earth, water, air, and fire were the 4 elements
Leucippus and Democritus argued that these atoms were the building blocks of all matter, differing in size and shape, which determined the properties of the substances they composed.
There’s no science ot background to this. They're rationalizing these ideas. Philosphophers thinking.
Democritus’s work was left
John Dalton:
First atomic theory: contributions of all works into one.
GB professor
Theory: the theory is that atoms are the fundamental building block of matter.
Dlaton’s Postulates: Each element is composed of extremely small particles called atoms. Wrong: Different isotopes/subotmaic particles prove this wrong.
All atoms of an element are identical to one another in mass, and other & the different atoms of different elements are different.
Alchami: Cheap metlas → precious metals. YOU CANNOT CHANGE TO ONE ELEMENT TO ANOTHER.
Can you change elements of one element to another? Yes, nuclear decay. This process involves the transformation of one atomic nucleus into another, resulting in the emission of particles and energy. Nuclear pwr plants is this from matter → energy.
In ordinary chemical reactions, matter is neither created nor destroyed.
Matter = condensed energy.
Matter cannot be created nor destroyed in ordinary chemical reactions
You end up with the same, but they’re different in combo.
Compounds are formed when atoms of more than one element combine; a given compound always has the same relative number and kind of atoms. Derived from the law of composition.
(Both below are still apart of theory)
Law of constant composition: (Joseph Proust)
Also known as the law of definite proportions
The elemental composition of a pure substance never varies.
Law of multiple propositions:
When two elements combine to form more than one compound, the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.
The two elements that make up carbon and oxygen. The compound was analyzed for its masses, the mass ratio of oxygen to carbon was 1. for every gram of carbon, 1.33 gram of oxygen.
More oxygen leads to a mass raito of oxgygen to carbon of 2.667. every gram of carbon, 2.667 7 grams of oxygen are needed to fully react, which illustrates the importance of maintaining the correct proportions for optimal combustion in chemical reactions.
When 2 elements form 2 different compounds, the mass ratio of elements in one compound is related to the mass ratio in the other by a small whole number.
Law of Conservation of Mass:
The total mass of substances present at the end of a chemical process is the same as the mass of substances present before the process took place.
Antoine Lavoisier:
Sir Humphrey Davy:
Used electrolysis to isolate potassium and sodium, contributing significantly to the understanding of chemical reactivity and the properties of elements.
There are electrical forces holding atoms together.
William Crookes:
Cathode ray tube, opeening the way for new research
The battery used in the cathode ray tube caused a glowing color due to the excitation of gas particles within the tube, which in turn produces streams of electrons.
Michael Faraday:
Physicists experimented with the passage of electraicity between metal electrodes fused to glass tubes that wweere partially evacuated.
Beam must be coming from atoms
Negative catho & + anode, which caused it to be a negative thing be made up of.
When a magnet placed perependicualr over the beam, the beam gets deflected and in the way a negative thing behaves in an electric field.
Observations:
Rays are emitted from the cathode
travel in a straight line
cause fluoresnece
deflected by a magnet in a direction expected for negatively charged particles
The materials have no effected on cathode rays.
Atoms have parts, as a result from the testing.
Sir. JJ Thompson:
GB Noble oriot
Credited for measuring the mass-to-charge ratio for an electron.
Measured the delfection of thre reays in magentic & eletreic feilds. Confirmed negative.
He showed that delfections were the same no matter what gas was used.
This storngly confiremd tha the rays were not gaseous ions but instead negatively charged particle contrinaed in all matter.
Knowing the battery charge fixed it
cAthod ray is deflected by a magentie field and then bent abck an eletric field to the un-deflected postion
the strenghts of the fields are both used to calcultate the mass to crhage ratio.
mass of electron is ingisificnant
Thompson’s experiment tool needs to be known
Phosphorus screen
Thomson:
Cathode rays are negative
Deflections were the same no matter what he used
He didn’t use gaseous ions. No matter what gas was used.
(Model is something used that is really something small or too big.)
HE determined the charge to mass ratio by the electron. by knowing the strength of the electric field and the magnetic field.
Mass is insignificant to its charge. Hair on your weight.
Plumb-pudding model. Dalton saw atom as industrcuble parts, now we have that model. He saw spherical plasma, or postivly charged conteents, with these negative charged particles embeded in them.
Canal rays: Beamt that demonstrated that teh glow was negative and that particles must exist within atoms, helping to further our understanding of atomic structure and leading to the discovery of the electron. Led to the discovery of the protons.
Cathode = negative charge.
Robert Milikan’s Oil Drop
Atomizer filled with oil was used to create small drops of oil that could be manipulated by electric fields, allowing Milikan to measure the charge of an electron accurately. Holes with anode fall through and zaps them with x rays and
They were all multiples to the same charge.
Milikan find the charge of an electron.
Earnest Rutherford”
Wanted to show that the atom is moslty empty space
Alpha particle = positive charge
Beta particles were made up of high speed particles.
Gold foil experiment. Takes alpha particles and directs them at a thin layer of gold foil to observe the scattering pattern, demonstrating that most alpha particles pass through without deflection, indicating the absence of substantial mass in atoms. This led to the conclusion that atoms consist primarily of empty space, with a small, dense nucleus at the center where the mass is concentrated.
A particle is barely reflected back, supporting the idea that the nucleus occupies a small volume compared to the overall size of the atom.
Discovers nucleus
(INSERT PICTURE OF HIS NUCLEAR MODEL)
Pea in football field and bee buzzing at 400 ft would be that good model.
Mass of an toaotm is not equal to tehe mass of electrons in the atom.
Chadiwick:
Strong fofce holds neutrons and protons inside a nucleus
Explained why the mass of the atom was different
Proton = 1.0073 amu & +1
Neutron = 1.0087 amu & neutral
Electron = 5.486 × 10-4. (NO) & -1
Elemntal symobl
Atomic number all atoms of the same element have the smae number of protons. Atomic number (number of protons or electrons) Has to have 6 protons to have 6 protons
Not all carbons have an atomic. Mass number = number of protons & neutrons MASS NOT A NUMBER.
Isotp[te:
Atoms of the same element with different masses
Isotopes have different numbers of neutrons
11C & 6C = 5 nuetrons
12C & 6C = 6 neutrons
13C & 6C = 7 neutrons
Mass-spectrosipy: This technique allows for the precise measurement of the mass-to-charge ratio of ions, enabling the identification and quantification of different isotopes in a sample. A magnetic field bends an electron.
Weighted-average is needed to be learned.
(Abundance times the mass) + (Abundance times the mass) + (Abundance times the mass). DO NOT DIVIDE BY 3.
Adding them up & dividing by three is incorrect. Instead, the proper method requires using the total abundance and mass for each isotope to find the weighted average, ensuring accurate representation of isotopic composition.
Cation = Positive
Anion = Negative
one more proton than electron is a net plus one