1 / 24

Atomic Theories

Atomic Theories. BrainPOP : Atomic Model. Democritus: 400 B.C. Coined the word “atom” C omes from the Greek a- tomos meaning uncuttable or indivisible. Dalton: Early 1800s. Father of the “Modern Atomic Theory”

lisbet
Download Presentation

Atomic Theories

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Atomic Theories BrainPOP: Atomic Model

  2. Democritus: 400 B.C. • Coined the word “atom” • Comes from the Greek a-tomosmeaninguncuttable or indivisible

  3. Dalton: Early 1800s • Father of the “Modern Atomic Theory” • All matter is made up of tiny indivisible particles called atoms. • Atoms of the same element have identical properties, including identical mass. • Atoms of different elements have different properties, including different mass. • Atoms combine in fixed whole number ratios to form compounds. • A specific compound is always made up of atoms in a specific proportion.

  4. Dalton: Early 1800s • Determined that each element corresponds to a unique atom • Developed a system of chemical symbols based on atomic mass • Compounds are atoms linked as molecules

  5. Discovery of the Electron • In 1897, J.J. Thomson used a cathode ray tube to deduce the presence of a negatively charged particle. • Cathode ray tubes pass electricity through a gas that is contained at a very low pressure.

  6. Thomson: Late 1800s • A neutral atom is made up of an equal number of positive and negative particles. • Electrons were like plums embedded in a positively charged “pudding”, thus it was called the “plum pudding” model.

  7. Rutherford: Early 1900s • Determined that the nucleus of the atom is extremely small and positively charged. • The rest of the atom is mostly empty space and contains electrons. • Rutherford’s Gold Foil Experiment • Using alpha particles as bullets, he knocked hydrogen nuclei out of atoms of 6 elements. • He named them protons, from the Greek word for “first.”

  8. Rutherford’s Gold Foil Experiment  Model of Rutherford’s Atom 

  9. Bohr • RULE 1: Electrons can orbit only at certain allowed distances from the nucleus. • RULE 2: Atoms radiate energy when an electron jumps from a higher-energy orbit to a lower-energy orbit. • Also, an atom absorbs energy when an electron gets boosted from a low-energy orbit to a high-energy orbit.

  10. Bohr’s Atomic Model

  11. Quantum Theory • Electrons are distributed around the nucleus in "probability regions" called "atomic orbitals". • Electrons behave like waves and particles.

  12. Atomic Models

  13. Atomic Structure

  14. Intro to Atoms • Matter has mass and takes up space. • Atoms are basic building blocks of matter, and cannot be chemically subdivided by ordinary means.

  15. Composition of Atoms • Atoms are composed of three types of particles: • Protons • Neutrons • Electrons

  16. Protons, Neutrons, and Electrons • Protons and Neutrons are responsible for most of the atomic mass • The mass of an electron is very small • In the nucleus • Protons (positive charge) • Neutrons (no charge) • Outside the nucleus • Electrons (negative charge)

  17. Atomic Number • The number of protons determines the atomic number of an element. • The elements are placed in order by increasing atomic number on the periodic table.

  18. Atomic Mass • The total number of protons and neutrons that make up the nucleus of an atom. • To find the number of neutrons… Mass number – atomic number = # of neutrons • EX: Uranium-235 Mass number – atomic number = neutrons 235 (protons + neutrons) – 92 protons = 143 neutrons

  19. Uh…how is that again? • To find the number of protons, electrons and neutrons in an atom, just follow these easy steps: • Step 1 - Gather Information • Step 2 - The Number of Protons is... • Step 3 - The Number of Electrons is... • Step 4 - The Number of Neutrons is...

  20. Step 1 - Gather Information • Look up the element on the periodic table. • Use the table to find the element’s atomic number and atomic mass (weight). • The atomic number is located at the top, while the atomic mass is located at the bottom.

  21. Step 2 - The Number of Protons is... • The atomic number is the number of protons in an atom of an element. • How many protons are in Krypton?

  22. Step 3 - The Number of Electrons is... • Atoms must have equal number of protons and electrons. • Therefore, in an atom of Krypton, there must be 36 electrons since it contains 36 protons. • An atom can gain or lose an electron, becoming an ion. • Adding or removing electrons does not change what the element is; it just changes its net charge.

  23. Step 4 - The Number of Neutrons is... • Look for the atomic weight/mass on the periodic table. • Round the atomic weight to the nearest whole number to get the mass number. • So for Krypton… • Mass number = # of protons + # of neutrons • 84 = 36 + # of neutrons • 84-36= 48 neutrons!

  24. In summary… For any element… • # of Protons = Atomic # • # of Electrons = # of Protons = Atomic # • # of Neutrons = Mass # - Atomic #

More Related