• Atomic theory Democritus(400BC): All Substances of tiny indivisible particles called atom.• John Dalton(1808): 1. All matter consisted of small indivisible particle. 2. Atom of same element are alike 3. Atoms are combined in simple whole number ratios. J.J Thomson(1897): Atom is a sphere of positive matter in which electrons are positioned by electrostatic forces. Major portion of the atom is empty. Rutherford The whole mass of the atom is concentrated in the centre of atom called nucleus. The positively charged particles are present in the nucleus of atom. The electrons revolve around the nucleus in different circular orbits. Size of nucleus is very small as compare to the size of atom.
Short video on atom http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/ fundamentals/
Introduction to the Periodic TableAtomic Number ● Symbol ● Atomic WeightElement ● Compound ● Mixture
What is the ATOMIC NUMBER? o The number of protons found in the nucleus of an atom Or o The number of electrons surrounding the nucleus of an atom.
What is the SYMBOL?o An abbreviation of the element name.
What is the ATOMIC WEIGHT? o The number of protons and neutrons in the nucleus of an atom.
How do I find the number of protons,electrons, and neutrons in an elementusing the periodic table?o # of PROTONS = ATOMIC NUMBERo # of ELECTRONS = ATOMIC NUMBERo # of NEUTRONS = ATOMIC _ ATOMIC WEIGHT NUMBER
Video on periodic tablehttp://www.bbc.co.uk/schools/gcsebitesize/science/aqa/fundamentals/theperiodictableact.shtml
Google web side to learnmore about periodic table www.chemicalelements.com/ Home Work Go to web side and make brief notes of page 1 and 2. Draw atomic structure and clearly mention number of electron, proton, and neutron.
What is an ELEMENT?o A substance composed of a single kind of atom.o Cannot be broken down into another substance by chemical or physical means.
What is a COMPOUND? o A substance in which two or more different elements are CHEMICALLY bonded together.
What is a MIXTURE?o Two or more substances that are mixed together but are NOT chemically bonded.