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MATTER, ELEMENTS, & ATOMIC STRUCTURE MATTER • Matter is anything that has mass and takes up space. • Ex: buildings, a fork, air, your clothes, etc… • . ELEMENTS • Elements are the simplest pure substances, and they cannot be broken down into any other substances. • Elements are often called the building blocks of matter because all matter is composed of one element or a combination of two or more elements. WHAT IS AN ATOM? • An atom is the smallest particle of an element (or unit of matter) that retains the identity of the substance. ATOMIC STRUCTURE • ATOMS ARE COMPOSED OF 2 REGIONS: • NUCLEUS: THE CENTER OF THE ATOM THAT CONTAINS THE MASS OF THE ATOM • ELECTRON CLOUD: REGION THAT SURROUNDS THE NUCLEUS THAT CONTAINS MOST • OF THE SPACE IN • THE ATOM Nucleus Electron Cloud ELECTRON CLOUD EACH ATOMIC SHELL CAN HOLD A CERTAIN NUMBER OF ELECTRONS BEFORE IT IS FULL. ONCE THAT SHELL IS FULL, THE ELECTRONS WILL FILL THE NEXT SHELL. WHAT’S IN THE NUCLEUS? The nucleus contains 2 of the 3 subatomic particles: Bohr Model • Protons (p+) : positively charged subatomic particles • Neutrons (n0): neutrally charged subatomic particles WHAT’S IN THE ELECTRON CLOUD? • The 3rd subatomic particle resides outside of the nucleus in the electron cloud. • Electron (e-): the subatomic particle with a negative charge and relatively no mass HOW DO THESE PARTICLES INTERACT? • PROTONS AND NEUTRONS LIVE COMPACTED IN THE TINY, POSITIVELY CHARGED NUCLEUS ACCOUNTING FOR MOST OF THE MASS OF THE ATOM. • THE NEGATIVELY CHARGED ELECTRONS ARE SMALL AND HAVE A RELATIVELY SMALL MASS BUT OCCUPY A LARGE VOLUME OF SPACE OUTSIDE THE NUCLEUS. HOW DO THE SUBATOMIC PARTICLES BALANCE EACH OTHER? • In an uncharged atom: • The protons = the electrons • If 20 protons are present in an atom then 20 electrons are there to balance the overall charge of the atom—atoms are neutral or uncharged. • The neutrons have no charge; therefore they do not have to equal the number of protons or electrons. THE PERIODIC TABLE THE PERIODIC TABLE OF ELEMENTS ARE BROKEN INTO 3 CATEGORIES: METALS, NONMETALS, AND METALLOIDS. They can be broken down into 10 more specific categories Metals have properties (with some exceptions) They are solid (with the exception of mercury, Hg, a liquid). They are shiny, good conductors of electricity and heat. They are ductile (they can be drawn into thin wires). They are malleable (they can be easily hammered into very thin sheets). All these metals tend to lose electrons easily. The following figure shows the metals. NONMETALS HAVE PROPERTIES OPPOSITE THOSE OF THE METALS. THE NONMETALS ARE BRITTLE, NOT MALLEABLE OR DUCTILE, POOR CONDUCTORS OF BOTH HEAT AND ELECTRICITY, AND TEND TO GAIN ELECTRONS IN CHEMICAL REACTIONS. SOME NONMETALS ARE LIQUIDS. METALLOIDS THE METALLOIDS, OR SEMIMETALS, HAVE PROPERTIES THAT ARE SOMEWHAT OF A CROSS BETWEEN METALS AND NONMETALS. METALLOIDS TEND TO BE ECONOMICALLY IMPORTANT BECAUSE OF THEIR UNIQUE CONDUCTIVITY PROPERTIES (THEY ONLY PARTIALLY CONDUCT ELECTRICITY), WHICH MAKE THEM VALUABLE IN THE SEMICONDUCTOR AND COMPUTER CHIP INDUSTRY. EACH ELEMENT HAS A PERIOD NUMBER AND GROUP NUMBER The period number is determined by the horizontal column that an element falls within The group number is determined by the vertical column that an element falls within Where Do You Find “these” Numbers? Atomic Number Symbol Name Atomic Mass (this is an average, always round) electrons protons Atomic number equals the number of _________or __________. protons + ___________. neutrons Atomic mass equals the number of _________ HOW DO WE KNOW THE NUMBER OF SUBATOMIC PARTICLES IN AN ATOM? Atomic number: this number indicates the number of protons in an atom. • Ex: Helium’s atomic number is 2 • So helium has 2 protons • Ex: Carbon’s atomic number is 6 • So carbon has 6 protons **The number of protons identifies the atom. Ex. 2 protons = He, 29 protons = Cu • Atomic Mass is the mass of an atomic particle or element WHAT ABOUT THE ELECTRONS? • The electrons are equal to the number of protons (in an uncharged/neutral atom). • So e- = p+ = atomic # WHICH ELEMENT IS SHOWN? DETERMINE THE NUMBER OF SUBATOMIC PARTICLES IN THE FOLLOWING: Cl has a mass # of 35 and an atomic # of 17 p+ = ____, no = ____, e- = ____ K has a mass # of 39 and an atomic # of 19 P+ = ___, no = ___ e- = ____