The study of matter and the changes matter undergoes
The study of properties and behavior of matter
Chemistry is important because it has to do with everything in our daily lives
Atom
The small building blocks of matter
The basic unit that makes up all matter or basic unit of element that can enter also into the chemical reaction
Atom
It consists of a positively charged core (the atomic nucleus) which contains protons and neutrons, and which maintains a number of electrons to balance the positive charge in the nucleus
Atoms are electrically neutral species and must contain the equal number of electron and protons
Plato and Aristotle believed that matter did not exist as a discrete units and atoms are considered continuous particles
Dalton's Atomic Theory
Elements are composed of extremely small particles, called atoms
All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements
Compounds are composed of atoms of more than one element. In any compound, the ratio of the numbers of atoms of 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
Law of Conservation of Mass states that matter can either be created nor destroyed
Modern Atomic Theory
Atoms may be disintegrated. In nuclear reactions, atoms are being transferred into atoms of single elements in a process known as nuclear transmutation
Not all atoms of any given element are alike
Not all atoms of a given element pose identical properties except in mass
Atoms of different elements have different properties
Electron
Discovered by Joseph John Thomson
A mass of 9.109 x 10-31 kg
A charge of -1.602 x 10-19 coulombs
Proton
One of the components of a nucleus
Discovered by Eugene Goldstein
A mass of 1.673 x 10-27 kg
Charge of +1.602 x 10-19 coulombs
Neutron
Another component of a nucleus
Discovered by James Chadwick in 1932
A mass of 1.675 x 10-27 kg
Has no charge or no charge
Particle
Electrons
Protons
Neutrons
Solid Sphere Model (John Dalton 1803)
Dalton drew upon the ancient Greek idea of atoms (the word atom comes from the Greek atomos meaning indivisible)
His theory stated that atoms are indivisible, those of a given element are identical, and compounds are combinations of different types of atoms
Recognized atoms of a particular element differ from to other elements
Plum Pudding Model (J.J. Thomson 1904)
Thomson discovered electrons (which he called "corpuscles") in atoms in 1897, for which he won a Nobel Prize. He subsequently produced the "plum Pudding" model of the atom. It shows the atom as composed of electrons scattered throughout a spherical cloud of positive charge
Recognize electrons as component of atoms
No nucleus; didn't explain later experimental observations
Nuclear Model (Ernest Rutherford 1911)
Rutherford fired positively charged alpha particles at a thin sheet of gold foil. Most passed through with a little deflection, but some deflected at large angles
This was only possible if the atom was mostly empty space, with a positive charge concentrated in the center: the nucleus
Realize positive charge was localized in the nucleus of an atom
Did not explain why electrons remain in orbit around the nucleus
Planetary Model (Niehls Bohr 1913)
Bohr modified rutherford's model of the atom by stating that electrons move around the nucleus in orbits of fixed sizes and energies. Electron energy in this model was quantized; electrons could not occupy values of energy between the fixed energy levels
Proposed stable electron orbits explain the emission spectra of some elements
Moving electrons should emit energy and collapse into the nucleus, model did not work well for heavier atoms
Quantum Model (Erwin Schrodinger 1926)
Schrödinger stated that electrons do not move in set paths around the nucleus, but in waves. It is impossible to know the exact location of the electrons; instead, you have clouds of probability called orbitals, in which we are more likely to find an electron
Shows electrons didn't move around the nucleus in orbits but in clouds where their position is uncertain
Still widely accepted as most accurate model of the atom
Thomson Model
Atoms is a spherical mass containing electrons and that this spherical mass is positive but is made neutral by the electrons embedded in it
Aka Plum Pudding Model
Rutherford Model
It is based on additional experimental evidence of "alpha scattering experiments"
The positive charges or the protons are concentrated in the nucleus and the region outside the nucleus is occupied by electrons
Bohr Model of an Atom
In this model, protons are in the nucleus and the electrons are in the orbital motion around the nucleus
Electrons may be found in any several definite orbits around the nucleus
Rutherford-Bohr Model
In this model, the atoms are in elliptical orbits of increasing number
Heisenburg Uncertainty Principle
This principle states that simultaneous determination of the exact position and exact momentum of electron is impossible
Wave Mechanical Atom
Aka Electron Cloud Model
In this model, the nucleus is a single cluster of particles at the center of the atom while the electrons are everywhere
Has dense positive charge nucleus at the center and electrons still have a distinct amount of energy which are usually place outside the nucleus
The electrons are not orbiting the nucelus in definite or fixed pathways. Instead of orbiting, the electrons are placed in orbitals outside the nucleus (electrons are still orbiting the nucelus but not in fixed pathways)
Schroedinger "Quantum Model"
This theory makes the assertion that electromagnetic radiation like X-rays, gamma rays, radio waves and light rays are made up of small bits of energy
Pauli's Exclusion Principle states that no two electrons can have the same set of quantum numbers
Quantum Numbers
Principal Quantum Number (n)
Azithmuthal Quantum Number (l)
Magnetic Quantum Number (m)
Spin Quantum Number (s)
Orbital Theory
This theory states that the number of orbital types in a given shell is equal to the shell number
Orbitals have a three-dimensional region in space where the probability of finding the electron is greatest
Hund's Rule of Maximum Multiplicity - orbitals with the same electron of same energy level must be filled in singly before pairing
Electron Configuration Theory
1st main energy level maximum number of 2e-
2nd main energy level maximum number of 8e- (2s, 6p)
3rd main energy level maximum number of 18e- (2s, 6p, 10d)
4th main energy level maximum number of 32e- (2s, 6p, 10d, 14f)
Aufbau Principle
states that atoms may be built by progressively filling the main energy levels, sub levels and orbitals with electrons according to increasing level
Atomic Number (Z)
atomic number is equal to the number of protons and electrons
number of protons in the nucleus of an atom of an element
also the number of electrons in an atom
this quantity is fundamental to the identity of each element because it is related to the electrical make-up of atom
Mass Number (A)
total number of protons and neutrons on the nucleus of nucleons
Nuclear Notation
A (Mass number)
N (Neutrons)
Z (Atomic number)
X (Element)
Isotopes
atoms of the same element with the same atomic number, but different mass numbers
in other words, they have the same number of protons and electrons but different number of neutrons
Isotopes
12Carbon and 13Carbon are the 2 stable isotopes of Carbon. However, 12Carbon is more abundant constituting 98.89% of all Carbons
14Nitrogen and 15Nitrogen are two stable isotopes of N. However, 14Nitrogen makes up 99.63% of all Nitrogen
Isotones
atoms of different elements having the same number of neutrons
Isobars
atoms of different elements having the same atomic mass
Ions
it is a charged species, an atom or a molecule, that has lost or gained one or more electrons
Cation (if neutral atom losses one or more electrons, it will have a net + charge)
Anion (if the atom gains electrons, it will have a net - charge)
Molecules
it is the smallest indivisible portion of a pure chemical substance that has its unique set of chemical properties, that is, its potential to undergo a certain set of chemical reactions with other substances
aggregates of at least two atoms in a definite arrangement and held together by chemical forces
Electrodes
a conductor that is used to make contact with non-metallic part of a circuit
commonly used in electrochemical cells, semi-conductors such as diodes and other medical devices
classified as Anode and Cathode depending on the current that is flowing into or out of the electrode