Atomic Theory Scientists
Atomic Theory ScientistsThe history of the atom.
HISTORY OF THE ATOM- Democritus460 BCDemocritus develops the idea of atomsHe pounded up materials in his pestle andmortar until he had reduced them to smallerand smaller particles which he called ATOMOS (greek for indivisible) This is where we get the word “atoms”
History of the Atom- Aristotle Aristotle said there were four elements:– Earth– Air– Water– Fire
Boyle Boyle rejected the idea that there were 4 elements– Impossible to combine the 4 elements to form a substance– Impossible to extract these elements from a substance Boyle defined an element as any substance that cannotbe decomposed into a simpler substance
HISTORY OF THE ATOM- DaltonJohn Dalton1808Dalton's Atomic Theory1) All matter is made of atoms. Atoms are indivisibleand indestructible.2) All atoms of a given element are identical in massand properties3) Compounds are formed by a combination of two ormore different kinds of atoms.4) A chemical reaction is a rearrangement of atoms.Dalton’s “Billiard Ball Model”:Atoms are the smallest type of matter and theyare entirely solid like a billiard ball
HISTORY OF THE ATOM- ThomsonJoseph John Thomson Found the electron using the cathode ray tube because ofits negative charge He found that atoms could sometimes eject a far smallernegative particle which he called an ELECTRON . Also developed the Plum Pudding Model of the atom
Thomson’s Plum Pudding ModelThompson develops the idea that an atom was made up ofelectrons scattered unevenly within an elastic sphere surroundedby a soup of positive charge to balance the electron's chargelike plums surrounded by pudding.PLUM PUDDINGMODEL
History of the Atom- MillikanRobert Millikan Discovered the charge and mass of anelectron by his famous oil dropexperiment– The experiment entailed observing tinycharged droplets of oil between two horizontalmetal electrodes. This enabled him to measurethe charge of an electron– calculated the mass of an electron, which is 9.1 1031 kg
What’s next? Two inferences:– Something had to account for the mass of the atom since the electrondoesn’t contribute to it– Since the charge on an atom is neutral, there must be a positivelycharged area to balance out the negative charge of the electron
HISTORY OF THE ATOM- RutherfordErnest Rutherford–He used his Gold Foil experiment to prove Thomson’s plumpudding model wrong, discovered protons, and developed theidea of a nucleus–He passed particles through gold foil, and realized noteverything passed through, so there must be something otherthan just a negative charge–He developed the Nuclear Atom model or the Planetary modelof the atom–Most of the mass of the atom is in the nucleus and electronsorbit the nucleus like planets orbit the sun
HISTORY OF THE ATOMhelium nucleigold foilhelium nucleiThey found that while most of the helium nuclei passedthrough the foil, a small number were deflected and, to theirsurprise, some helium nuclei bounced straight back.
History of the Atom- ChadwickJames Chadwick Chadwick took Rutherford’s researchfurther and found the neutron The problem was the atomic number was less than theatomic mass (average mass of the atom). For example,a helium atom has an atomic mass of 4, but an atomicnumber (or positive charge) of 2.Since electrons have almost no mass, it seemedthat something besides the protons in the nucleuswere adding to the mass. One leading explanation wasthat there were electrons and additional protons inthe nucleus as well -- the protons still contributedtheir mass but their positive charge was canceled outby the negatively charged electrons. idea that therecould be a particle with mass but no charge. He calledit a neutron, and imagined it as a paired proton andelectron.
Niels BohrNiels Bohr1913Bohr refined Rutherford's idea by addingthat the electrons were in orbits. Likeplanets orbiting the sun. With each orbitonly able to contain a set number ofelectrons. This is called Bohr model orQuantum model of the atom.
SchrodingerBohr’s model only fits hydrogen and was provenincorrect by Schrodinger.Schrodinger suggested that orbits were notalways circular, but in a pattern. He called themorbitals.Schrodinger’s model is called the QuantumMechanical Model of the atom
HeisenbergWerner Heisenberg The Heisenberg uncertainty principle states that itis impossible to know simultaneously the exactposition and momentum of a particle. That is, the more exactly the position is determined,the less known the momentum, and vice versa.
History of the Atom- Chadwick Chadwick took Rutherford’s research further and found the neutron The problem was the atomic number was less than the atomic mass (average mass of the atom). For example, a helium atom has an atomic mass of 4, but an atomic number (or positive charge) of 2. Since electrons have almost no mass, it seemed
Key Difference - Dalton’s Atomic Theory vs Modern Atomic Theory Dalton’s atomic theory is the oldest theory about the atom. In 1808, John Dalton published his theory, which was composed of several postulates that were built based on his experiments and laws of chemical combination. A number of scientists later contributed to the development of
shaped the atomic theory. Warm-Up Lesson Question Lesson Goals Atomic Theory Words to Know Fill in this table as you work through the lesson. You may also use the glossary to help you.? W 2K Describe the development of the . Explain how the atomic theory throughout history. How did the atomic theory
Physical & Chemical Properties Chemical & Physical Changes Matter Obj. 2.1.2 Atomic Structure Isotopes Matter Obj. 2.1.2 Rate Atomic Structure Obj. 2.1.4 Matter Obj. 2.1.2 Phase Change Test Matter Matter Atomic Structure Obj. 2.1.4 Atomic Structure Obj. 2.1.4 Atomic Structure Structure Atomic Structure Obj.
‘The Superheroes of the atomic model’ task covers the development of the atomic model in an active fact finding resource. This could be an initial lesson on the atomic model and the scientists that developed it into the current atomic
The Atomic Theory of Matter Dalton’s Atomic Theory Postulates 10 2. All atoms of a given element are identical, having the same size, mass and chemical properties. The atoms of different elements are different. Different elements have different atomic properties such as atomic mass.
Atomic Structure Timeline History of Atomic Theory. Essential Questions What does it mean when my science . perform controlled experiments like true scientists. Lavoisier 1777 French chemist, who is considered . This contradicted Dalton's Atomic Theory. This allowed a new model of the atom. J. J. Thomson (1903)
1.1. The Atomic Theory www.ck12.org 1.1 TheAtomicTheory Lesson Objectives The student will: give a short history of how the concept of the atom developed. describe the contributions of Democritus and Dalton to the atomic theory. summarize Dalton’s atomic theory and explain
may be taken on an instrument with only one manual. Consequently, in Grades 1–3, some notes may be transposed or omitted, provided the result is musically satisfactory. Elements of the exam All ABRSM graded Organ exams comprise the following elements: three Pieces; Scales, arpeggios and exercises; Sight-reading (with an additional Transposition exercise in Grades 6–8); and Aural tests .
