Presentation Properties of Atoms By : Vaibhav Sharma

Atoms Smallest particle that still retains properties All matter is made up of atoms Comes from Greek word atomos – meaning indivisible

Dalton’s Atomic Theory Matter is composed of atoms Atoms are indivisible Atoms of a given element are identical in size, mass, chemical properties Atoms of a specific element are different than those of another element

Components of the Atom Nucleus – consists of protons and neutrons Protons – positively charged Neutrons – neutral Mass of protons and neutrons are similar Electrons – orbit around the nucleus Negatively charged 1/2000 mass of a proton

Electron Orbits Electrons “orbit” around the nucleus, called “shells” Similar to planets orbiting around the sun Called the “Bohr Model” 2, 8, 8, ….

Bohr Models Carbon Bohr Model Calcium Bohr Model Argon Bohr Model

Valence Electrons Electrons in outermost shell Important for chemical reactions

Atomic Number & Mass Number Measures # of protons in the nucleus Also measures # of electrons in a neutral atom Mass Number Measures mass of the nucleus: # protons + # neutrons

Isotopes Different atoms may have different # neutrons – called isotopes Ex: Carbon-12 has 6 protons 6 neutrons, Carbon-14 has 6 protons 8 neutrons Different isotopes have different mass number.

Atomic Mass Weighted average of all isotopes – usually a decimal Based on abundance in nature Example: Chlorine-35, Chlorine-37: 35*0.7578+37*0.2422 = 35.45

Elements Pure substance that cannot be separated by physical or chemical means Made of only 1 type of atom Has unique properties

Periodic Table

Groups and Periods Groups are the columns on a periodic table 1,2,transition,3,4,5,6,7,8 Similar chemical properties in each column Periods are rows on the periodic table Goes from 1 to 7