Transcript Slide 1
Matter Anything that has mass and takes up space. All matter can be measured Mass Volume Density Hundreds of years ago, scientists found that certain types of matter couldn’t be broken down into any other simpler substances They called these special pure substances: elements No matter how small you divide it, gold is only made of gold atoms. So what is an atom? The smallest particle an element can be divided into and still maintain the properties of that element. Atoms are the building blocks of all matter. Why learn about atoms? All matter is made of atoms, atoms are the basic building block of everything in the universe What does an atom look like? The model of the structure of the atom has changed as technology has improved and as more evidence has been gathered. HISTORY OF THE ATOM 460 BC Democritus develops the idea of atoms He pounded up materials in his pestle and mortar until he had reduced them to smaller and smaller particles which he called ATOMA (greek for indivisible) First atomic models – roughly based on earth, air, water, and fire HISTORY OF THE ATOM 1808 John Dalton Suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOMS The new model of an atom- a tiny solid sphere HISTORY OF THE ATOM 1898 Joseph John Thompson found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRON 1904 Thompson develops the idea that an atom was made up of electrons scattered unevenly within an elastic sphere surrounded by a soup of positive charge to balance the electron's charge like plums surrounded by pudding. PLUM PUDDING MODEL The new model of an atom- atoms contain smaller, negatively charged particles 1910 Ernest Rutherford • English scientist who tested JJ Thompson’s model • Rutherford’s new evidence allowed him to propose a more detailed model with a central nucleus. • He suggested that the positive charge was all in a central nucleus. This held the electrons in place by electrical attraction Rutherford’s experiment His hypothesis: The results? The new atomic model- a dense, positively charged nucleus in the center surrounded by electrons 1913 Niels Bohr studied under Rutherford in Manchester, England Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons. Bohr’s Atom electrons in orbits nucleus The new atomic model- electrons are in orbits around the nucleus at different energy levels 1920’s Electron Cloud Model Electrons surround the positively charged nucleus, but not in set orbits They are in different levels, or clouds There are set amounts of electrons found in each cloud The new atomic model- set numbers of electrons are found in different cloud layers Atomic Model History http://www.youtube.com/watch?v=QbWK F9uDF7w https://www.youtube.com/watch?v=thnDx FdkzZs Neutron The neutron was not discovered until 1932 when James Chadwick This new idea dramatically changed the picture of the atom ATOMS AND ATOMIC STRUCTURE Atom Nucleus Proton Neutron Electron WHAT IS AN ATOM? o o The smallest unit of an element. Consists of a central nucleus surrounded by one or more electrons. WHAT IS THE NUCLEUS? o o o The central part of an atom. Composed of protons and neutrons. Contains most of an atom's mass. WHAT IS A PROTON? o o Positively charged particle. Found within an atomic nucleus. WHAT IS A NEUTRON? o o Uncharged particle. Found within an atomic nucleus. WHAT IS AN ELECTRON? o o Negatively charged particle. Located in shells that surround an atom's nucleus. Summary Particle Charge Mass (amu) Location Proton positive 1 nucleus Neutron neutral 1 nucleus Electron negative <1 shells outside the nucleus Atoms are neutral Since protons (positive charge) are equal to the numbers of electrons (negative charge), the overall charge of an atom is neutral Atoms as Pictured on the Periodic Table Atomic Number Symbol Name Atomic Mass protons electrons Atomic number equals the number of ____________ or ___________. neutrons protons Atomic mass equals the number of ______________ + ____________. (mass number) Ion charged particle formed when an atom gains or loses an electron Video of particles http://www.youtube.com/watch?v=lP57gE WcisY Bill Nye http://www.youtube.com/watch?v=aNK1 mQfNeik Let’s review The Atomic Number of an atom = number Protons of ______________ in the nucleus. (Equal to electrons) The Atomic Mass of an atom = number of Protons + neutrons _________ _________ in the nucleus. The number of Protons = Number of ____________. electrons _____________ orbit the nucleus. Electrons Build an atom http://phet.colorado.edu/en/simulation/bui ld-an-atom Atom arrangement animation http://web.visionlearning.com/custom/che mistry/animations/CHE1.3-ananimations.shtml http://www.bbc.co.uk/newsround/223694 68