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Atomic Structure

Atomic Structure. Robert Erwin Science 8 UMS Rockwall ISD. Atomic Structure. To understand how matter works, we need to understand what it’s made of – ATOMS . We use several tools to do so Models & numeric representations Scanning tunneling microscopes

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Atomic Structure

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  1. Atomic Structure Robert Erwin Science 8 UMS Rockwall ISD

  2. Atomic Structure • To understand how matter works, we need to understand what it’s made of – ATOMS. • We use several tools to do so • Models & numeric representations • Scanning tunneling microscopes • An Atom is the smallest unit of an element.

  3. Atomic Structure • An Atom is divided into two areas: • Nucleus • Electron Cloud

  4. Atomic Structure • Within those two areas, the Atom is Made up of three main particles • Proton (+) positively charged • Neutron (0) No Charge • Electron (-) Negatively charged

  5. Atomic Structure • Protons and Neutrons are in the nucleus • Electrons exist outside the nucleus in the electron cloud. • The # of Protons = the # Electrons in a stable atom.

  6. Atomic Structure • Almost all of the mass of an atom is in its nucleus • Proton = 1 Atomic Mass Unit • Neutron = 1 Atomic Mass Unit • Electron = 1/2000th Atomic Mass Unit • Add the Protons and Neutrons to get the Atomic Mass.

  7. Atomic Structure -Protons • Protons are in the nucleus • Protons have a mass of 1 AMU • The # of Protons in an atom determine what element it is. (Ex: If an atom has exactly 3 protons, it is ALWAYS Lithium) • The # of Protons in an atom is also = its Atomic Number.

  8. Atomic Structure - Neutrons • Neutrons are in the nucleus • Neutrons have a mass of 1 AMU • The # of Neutrons will usually be close to the # of Protons – but not always exactly the same. (Ex: Lithium has 3 Protons but 4 Neutrons) • Calculate the # of Neutrons by • Subtracting the atomic # from the atomic Mass. • Mass – protons = Neutrons

  9. Atomic Structure - Electrons • Electrons circle the nucleus in a cloud • Electrons have a mass of 1/2000th AMU • The # of Electrons will = the # of Protons in a stable atom. (Ex: Lithium has 3 Protons and 3 electrons) • Valence Electrons are the outermost electrons. • Valence Electrons determine an atom’s reactivity (how it behaves).

  10. Atomic Structure – Variations • An Ion is an atom where the # of Protons does not = the # of Electrons. • An atom with fewer electrons has a positive charge (+). • An atom with more electrons has a negative charge (-). • An Isotope is an atom that has more or fewer Neutrons, so has a different mass than the average balanced atom.

  11. Atom Models • We use the Bohr model to understand basic atomic structure. • Draw a circle and lightly shade it in- this is your nucleus. • Write “P+” inside the nucleus. This will be the # of Protons in your atom model. • Write “N” inside the nucleus. This will be the # of Neutrons in your atom model.

  12. Bohr Model • The Bohrmodel looked like a tiny solar system • The nucleus was represented in the center, like a star • The paths of the electrons looked like planets orbiting around the star. • Electrons orbit at different distances (Shells) from the nucleus due to different energy levels they hold • Each electron shell has a maximum number of electrons it can hold • The electron shells of the 1st 18 elements fill in a pattern of 2, 8, 8.

  13. Periodic Table of the Elements • Arrangement of elements into a table format • Each element is represented by a box labeled with a one or two letter symbol – Chemical Symbol unique to that element. • Shows Atomic Number (the number of Protons in the nucleus). • Shows Chemical Name. • Shows Atomic Mass – The AVERAGE mass of a balanced atom of that element

  14. An example of an entry in the periodic table. G atomic number 7 state of matter N element symbol nitrogen element name atomic mass 14.007 7 How many electrons? 7 How many protons? 7 How many neutrons?

  15. 7 G N nitrogen 14.007 The atomic mass is always rounded to the nearest whole number 14.007 to 14 26.560 to 27

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