Atomic Structure History leading to the discovery of the atom. And the methods used to analyze the structure of the atom.

Democritus 460B.C.-370B.C. Came up with the idea that if you kept cutting a piece of wood in half theoretically you would come upon a indivisible and indestructible thing that he called an atomos. The atom.

John Dalton Dalton’s Atomic Theory ( ) 1.All elements are composed of tiny-indivisible particles called atoms. 2.Atoms of the same element are identical. The atoms of any one element are different from those of any other elements. 3.Atoms of different elements can physically mix together or can chemically combine in simple whole number ratios to form compounds. 4.Chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element, however are never changed into atoms of another element as a result of a chemical reaction.

JJ Thomson Discovered the Electron by passing current through a cathode ray tube he was able to determine its negative charge by placing positive and negative plates above and below the tube. The negatively charged electron was attracted to the positively charged plate.

Ernest Rutherford ( ) The Atomic Nucleus By shooting alpha particles through gold foil Rutherford discovered that some particle bounced back. He concluded that the atom consisted of mostly empty space surrounding a tiny hard mass that had a positive charge. This charge is from the proton.

James Chadwick ( ) Chadwick confirmed the existence of yet another subatomic particle: the neutron Found in the atomic nucleus neutrons have no charge and but a mass nearly equal to the mass of the proton.

Properties of Subatomic Particles ParticleSymbolRelative Charge Relative Mass Mass of proton=1 Actual Mass In grams Electrone-e- 1-1/ x Protonp+p x Neutronn0n x10 -24

Quarks A quark (pronounced /kw ɔ rk/, kwork or /kw ɑ rk/, kwark) is an elementary particle and a fundamental constituent of matter. Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei.[1] Due to a phenomenon known as color confinement, quarks are never found in isolation; they can only be found within hadrons.[2][3] For this reason, much of what is known about quarks has been drawn from observations of the hadrons themselves. There are six types of quarks, known as flavors: up, down, charm, strange, top, and bottom.[4] Up and down quarks have the lowest masses of all quarks. The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state. For this reason, up and down quarks are generally stable and the most common in the universe, whereas charm, strange, top, and bottom quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators). Quarks have various intrinsic properties, including electric charge, color charge, spin, and mass. Quarks are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces (electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge. For every quark flavor there is a corresponding type of antiparticle, known as antiquark, that differs from the quark only in that some of its properties have equal magnitude but opposite sign. The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964.[5] Quarks were introduced as parts of an ordering scheme for hadrons, and there was little evidence for their physical existence until 1968.[6][7] All six flavors of quark have since been observed in accelerator experiments; the top quark, first observed at Fermilab in 1995, was the last to be discovered.[5]

Atomic Number The number of protons in an atom is the elements’ atomic number (z). What is the atomic number of this atom?

Atomic Mass The atomic mass is a number derived from the total protons and neutrons found in the atoms nucleus. The unit for atomic mass is AU. Which stands for Atomic Mass Unit. The electrons are not included in this because are so much lighter then the Protons and Neutrons. Example: Carbon has 6 protons and 6 neutrons its atomic mass therefore is 12

Practice Who coined the word atom? Who discovered the positively charged nucleus using the gold foil experiment? Who discovered the electron with his cathode ray tube experiments? Who discovered the neutron? An atom has 6 protons, 7 neutrons and 6 electrons: fill in the blanks Atomic Number is_____Atomic Mass____

Ions A neutral atom is one in that has an equal number of protons and electrons. Remember the protons have a positive charge and the electrons have a negative charge. When the numbers are not equal the atom is “charged”. An atom with a net charge is an Ion. They are written with the net charge in superscript like this C +4. How many protons and electrons are in this ion? #Protons_____ #Electrons_____

Isotopes Isotopes are atoms that have different atomic masses due to the fluctuation of the number of neutrons in an atom. These occur naturally, but can also be man made. The are written many ways but most frequently with their symbol a hyphen and their atomic mass. Example: C-14, C-13, C-12 Find the number of protons and neutrons C-14 P + ___, N 0 ____ C-13 P + ___, N 0 ____ C-12 P + ___, N 0 ____

Fill in the missing numbers from the following table. #p + #n 0 #e - Atomic Mass Atomic Number Symbol N-13 Cl-37