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4-1: Introduction to Atoms. How did the atomic theory develop and change into the modern model of the atom?. Anticipatory Set. Here come the atoms!. video. California Standards.
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4-1: Introduction to Atoms How did the atomic theory develop and change into the modern model of the atom?
Anticipatory Set Here come the atoms! video
California Standards • Science Standard 8.3.a: Students know the structure of the atom and know it is composed of protons, neutrons, and electrons. • Science Standard 8.7.b: Students know each element has a specific number of protons in the nucleus (the atomic number) and each isotope of the element has a different but specific number of neutrons in the nucleus.
Input • atom: smallest particle of an element. • electron: negatively charged particles in an atom. • nucleus: the central core of an atom • proton: positively charged particles in an atom’s nucleus. • energy level: the specific amount of energy an electron has.
Input • neutron: small particle in the nucleus of an atom with no electrical charge • atomic number: the number of protons in the nucleus of an atom. • isotope: atoms of the same element that have different numbers of neutrons. • mass number: the sum of the protons and neutrons in the nucleus of an atom.
Input • Development of Atomic Theory • Atomic theory has changed many times over the years. As more evidence was collected, the theory and models were revised. • Around 430 B.C., • a Greek philosopher, Democritus, • Idea= matter is formed of small pieces that could not be cut into smaller parts. • atomoswhich means “uncuttable”
Input & Modeling • Dalton’s Atomic Theory • thought that atoms were like smooth, hard balls that could not be broken into smaller pieces.
Input & Modeling • Dalton’s Atomic Theory • All elements are composed of atoms that cannot be divided. • All atoms of the same element are exactly alike and have the same mass. Atoms of different elements are different and have different masses. • An atom of one element cannot be changed into an atom of a different element. Atoms cannot be created or destroyed in any chemical change, only rearranged. • Every compound is composed of atoms of different elements, combined in a specific ratio.
Input & Modeling • Thomson’s Atomic Theory • In 1897, English scientist J.J. Thompson found that atoms contain negatively charged particles. • The negatively charged particles later became known as electrons. Thomson suggested that atoms had negatively charged electrons embedded in a positive sphere.
Input & Modeling • Rutherford’s Atomic Theory • In 1911, Ernest Rutherford found evidence that countered Thompson’s model. • His team discovered the positive charge (proton) + in an atom is clustered in the center (nucleus). According to Rutherford’s model, an atom was mostly empty space.
Input & Modeling • Bohr’s Atomic Theory • In 1913, Niels Bohr, a Danish scientist, suggested that electrons move in specific orbits around the nucleus of an atom.
Input & Modeling • Cloud Model • In the 1920’s, scientists determined that electrons do not orbit the nucleus like planets, but rather could be anywhere in a cloudlike region. • (SO WAS BOHR RIGHT?) • An electron’s movement is related to its energy level, or the specific amount of energy it has. • Electrons of different energy levelsare likely to be found in different places.
Input & Modeling • The Modern Atomic Model • In 1932, English scientist James Chadwick discovered another particle, the neutron, in the nucleus of atoms.
Input & Modeling • The Modern Atomic Model • At the center of the atom is a tiny, massive nucleus containing protons and neutrons. • Surrounding the nucleus is a cloudlike region of moving electrons. • The particle was difficult to detect because it has no charge.
Input • Particles in an Atom • An atom is composed of positively charged protons, neutral neutrons, and negatively charged electrons. Protons and neutrons are about equal in mass. An electron has about 1/2,000 the mass of a proton or neutron.
Input • Isotopes • Atoms of all isotopes of carbon contain six protons and six electrons, but they differ in their number of neutrons. Carbon-12 is the most common isotope.
Check forUnderstanding • What is located in a cloudlike region surrounding the nucleus in the modern atomic model? electrons • According to Dalton, all elements are composed of atoms that cannot be ___. divided
Guided Practice • Answer #1-4 Independent Practice • Finish the worksheet. • Complete the extension.
EXTENSION • Write a detailed SUMMARY of the section and complete the UNANSWERED QUESTIONS section of your notes. • Choose two of the remaining Depth & Complexity ICONS in your notes and explain how they relate to this section. • Finish the Development of Atomic Theory Timeline Booklet.
