Atomic Structure

1. Atomic Structure Robert Erwin Science 8 UMS Rockwall ISD 2014 – 2015

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. • Turn to your neighbor and repeat 5 times • “An Atom is the smallest unit of an element”. • “Atoms are the building blocks of matter”.

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 (sub-atomic) particles • Nucleus • Proton (+) positively charged • Neutron (0) No Charge • Electron Cloud • Electron (-) Negatively charged • Repeat this 3 times to your Neighbor.

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 neutralatom.

6. Atomic Structure • What is the smallest unit of an element? • What is the building block of all matter? • What are the two areas of an atom? • What are the three sub-atomic particles? • Where do we find each? • What are their electrical charges? • Repeat this 3 times to your neighbor.

7. Atomic Structure • Almost all of the mass of an atom is in its nucleus, made up of: • Proton = 1 Atomic Mass Unit • Neutron = 1 Atomic Mass Unit • Electron Cloud has very little mass, made up of: • Electron = 1/2000th Atomic Mass Unit • Add the Protons and Neutrons to get the Atomic Mass. • Omit the electrons, as they don’t have enough mass to calculate at this level.

8. 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.

9. Atomic Structure - Neutrons • Neutrons are in the nucleus • Neutrons have a mass of 1 AMU • The # of Neutrons will oftenbe close to the # of Protons – but not always exactly the same. (Ex: Lithium has 3 Protons but 4 Neutrons)

10. 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 neutralatom. (Ex: Lithium has 3 Protons and 3 electrons) • Valence Electrons are the outermost electrons. • Valence Electrons determine an atom’s reactivity (how it behaves).

11. 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.

12. Niels Bohr - 1913 • We use his model to understand basic atomic structure. • We do not think that this is what an atom actually looks like • It is a useful tool to help us understand atomic concepts

13. 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.

14. Dimitri Mendeleev - 1869 • Russian scientist who categorized the known elements. • Accurately predicted elements that had not yet been discovered. • Created the modern Periodic Table of the Elements.

15. Rephrased – TV Sitcom WKRP • Station DJ mentor teaching local gang member about atomic structure • Made a bet with him to get him to stay in school • What will take for you? If you don’t get it – let someone know. • There are LOTS of ways to learn • http://www.youtube.com/watch?v=hhbqIJZ8wCM