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Atoms and elements

Atoms and elements. Matter …. Is Everything ! It’s the amount of mass in an object Measured in kilograms It has volume: takes up space Measured in milliliters or cubic centimeters All matter is composed of elements only about 50 basic elements.

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Atoms and elements

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  1. Atoms and elements

  2. Matter…. • Is Everything! • It’s the amount of mass in an object • Measured in kilograms • It has volume: takes up space • Measured in milliliters or cubic centimeters • All matter is composed of elements • only about 50 basic elements Analogy: alphabet letters – words – sentences – books!

  3. Elements are… • Purest of the pure substances • There are 112 of them known so far • They are organized on the Periodic Table • The most common elements: 1. oxygen ( air, water, rock, living things) 2. Hydrogen (water, living things, sun, stars) 3. Nitrogen (air 80%, living things, soil) 4. magnesium, iron, aluminum, carbon

  4. Old Atomic Symbols The original chemical symbols of some of the older known elements were just that, symbols

  5. Naming elements • Physical properties such as their COLOR • Scientist: • Places: • Latin names: • Greekmythology: rubidium Curium, Einsteinium, Rutherfordium, Fermium Californium, Americinium, Europium Aurum (gold), Argentium (silver), Plumbium (copper) Helios (helium), mercury, plutonium

  6. Atomic Symbol • Universal (all countries) use the same symbols • 1 or two letter symbol • First letter is alwaysCAPITOL, second letter always lower case. Co (cobalt) is not same as CO (carbon monoxide) • Examples: • C for carbon • Ca for calcium • Cl for chlorine • Cf for californium CF C F Cf Not correct!!!

  7. fire earth air water Aristotle Early Greek Theories • 350 B.C - Aristotle • Theory that matter was made of four “elements”: earth, fire, water, air. • Aristotle was wrong. However, his theory persisted for 2000 years.

  8. The Greeks • 300 B.C. • Democritus a greek philosopher • The smallest “piece” of matter you could have: atomos: indivisible • They named the atom

  9. Atoms • Smallest part of an element. • Too small to be seen in ordinary light. • All atoms are made of the same basic ‘ingredients’ • Atoms vary in size and mass.

  10. John Dalton • 1800’s • Atoms are seen as solid, indestructible spheres (like billiard balls) • Proposed an Atomic Theory which states; - -Atoms of the same element have the same kind of atoms. -Atoms of different elements have different kinds of atoms. -Compounds are composed of atoms combined in specific ratios. -Atoms combine and rearrange yet mass is conserved Jelly beans

  11. The Electron • 1850’s • J. J. Thomson • A gas beam was repelled away by a magnet. • The gas is made of atoms, so…. • atoms must contain CHARGED particles! Magnet The beam was repelled (away) from the magnet!

  12. Thomson’s atomic model • Thomson found that there were small electrons embedded in the atom like chocolate chips in a chocolate chip cookie. • Atoms are solid spheres made-up of a solid positive mass (cookie) with tiny negative particles embedded in the positive core Negative electrons Positively charged cookie.

  13. Thomson’s electron model • Electrons are very small negatively charged particles. • (1/2000 the mass of a proton)

  14. Nucleus • 1905. Discovered by Earnest Rutherford in his famous ‘gold foil’ experiment. • He shot positively charged particles at a very thin piece of gold foil. He expected the particles to go right through the gold foil • But a few BOUNCED BACK! • THEY HIT SOMETHING SOLID!

  15. Rutherford’s gold foil experiment • This proved that: • the atom had a dense but very small positive core • the electrons were far away from the nucleus • Most of the atom is just EMPTY SPACE!

  16. That would be like a basketball (nucleus) on the 50 yard line, and you were an electron in a seat way up in the stands.

  17. Rutherford summarized that the nucleus must be… • Very small, dense,solid center of the atom • The nucleus has a positive charge • The electrons (negative) must be around the outside. • Most of the atom is empty space.

  18. Proton • Dense, positively charged particle • There are equal #of protons and electrons in a neutral atom. + = - • Proton # is their Atomic number. Ex: 6 protons is element 6 or carbon

  19. Neutron • Difficult to ‘find’ because they have no charge • Same mass as a proton, but has NO CHARGE (neutral) • Neutrons are in the nucleus. No charge

  20. Neils Bohr • 1920’s • Electrons move in orbits or energy levels around  the nucleus • Electrons can “jump” to different energy levels if they gain or lose energy.

  21. Quantum Mechanical Modelor Electron Cloud Model • Electrons move around the nucleus very fast. • You can’t predict where an electron will be at any moment. (Heisenburg Principle) • The analogy here is that of a "beehive" where the bees are the electrons and they ‘buzz’ around the nucleus.             

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