Subatomic Particles in an atom! 3 main particles in the atom:3 main particles in the atom: NeutronsNeutrons ProtonsProtons ElectronsElectrons In physics,

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Subatomic Particles in an atom! 3 main particles in the atom:3 main particles in the atom: NeutronsNeutrons ProtonsProtons ElectronsElectrons In physics, we will learn that even these particles are made of smaller particles! SIZE LOCATION

Remember, most of an atom is empty space! An atomic model the size of Busch Stadium and parking would contain a pea sized nucleus containing 95.95% of the atoms mass.An atomic model the size of Busch Stadium and parking would contain a pea sized nucleus containing 95.95% of the atoms mass. The pea at the pitcher’s mound would be the nucleus, and an ant crawling on the parking lot outside would be an electron!The pea at the pitcher’s mound would be the nucleus, and an ant crawling on the parking lot outside would be an electron! That is how much empty space is in an atom, and how tiny electrons are compared to the nucleus!That is how much empty space is in an atom, and how tiny electrons are compared to the nucleus!

ElectronsElectrons Discovered by JJ Thompson, RA MillikanDiscovered by JJ Thompson, RA Millikan Located around nucleusLocated around nucleus Negatively (-) charged particlesNegatively (-) charged particles Mass = essentially zero - only 1/2000 of a proton or neutronMass = essentially zero - only 1/2000 of a proton or neutron Charge = -1Charge = -1 Occupies the majority of space in an atom, but contributes NOTHING to the mass of an atom!Occupies the majority of space in an atom, but contributes NOTHING to the mass of an atom!

ProtonsProtons Eugen Goldstein (1886)Eugen Goldstein (1886) Located in….Located in…. The tiny, dense nucleus!The tiny, dense nucleus! Mass of 1.67 x 10 -24 gramsMass of 1.67 x 10 -24 grams We call that 1 amu, or a mass of 1We call that 1 amu, or a mass of 1 Charge = +1Charge = +1

NeutronsNeutrons James Chadwick (1932)James Chadwick (1932) Located in….Located in…. The tiny, dense nucleus!The tiny, dense nucleus! Mass of 1.67 x 10 -24 gramsMass of 1.67 x 10 -24 grams We call that 1 amu, or a mass of 1We call that 1 amu, or a mass of 1 Charge = 0Charge = 0

Nuclear Symbols X = element symbol Z = mass number = # protons + # neutrons A = atomic number = # protons (gives an element its identity!!) So… # neutrons = Z-A X Z A charge

Atomic Number Number of protonsNumber of protons Number on bottom of symbolNumber on bottom of symbol Gives an atom its identity!Gives an atom its identity! If 6 p + in nucleus, the atom is….If 6 p + in nucleus, the atom is…. Carbon!Carbon! It 7 p + in nucleus, the atom is….It 7 p + in nucleus, the atom is…. Nitrogen!Nitrogen! 12 6 C 7 14 N

Mass Number Mass Number = number of protons + number of neutronsMass Number = number of protons + number of neutrons Number on the top of the symbolNumber on the top of the symbol It tells you the mass of atom!It tells you the mass of atom! Not all atoms of the same element weigh the same!Not all atoms of the same element weigh the same! Two atoms of Carbon are shown below. One weighs 12, one weighs 14.Two atoms of Carbon are shown below. One weighs 12, one weighs 14. If they are both Carbon, the must both have the same number of…..If they are both Carbon, the must both have the same number of….. Protons! Each has…..Protons! Each has….. 6 protons! 6 protons! So different numbers of….So different numbers of…. Neutrons!Neutrons! How many neutronsHow many neutrons does each have? How would we figure that out? Mass Number - Atomic Number =Mass Number - Atomic Number = Number of neutrons 14 6 C C 12 6 6 neutrons! 8 neutrons!

ISOTOPESISOTOPES Atoms with same # Protons, but different # neutronsAtoms with same # Protons, but different # neutrons Example– 35 Cl and 37 Cl are isotopes of chlorineExample– 35 Cl and 37 Cl are isotopes of chlorine They only differ in their…..They only differ in their….. Mass!Mass! They both have how many protons….?They both have how many protons….? 17!17! Look at the periodic table, though - the periodic table lists the AVERAGE ATOMIC MASSLook at the periodic table, though - the periodic table lists the AVERAGE ATOMIC MASS For chlorine, it is 35.453 amu. This doesn’t look like an average between 35 and 37!For chlorine, it is 35.453 amu. This doesn’t look like an average between 35 and 37! That is because they don’t exist in nature 50-50!That is because they don’t exist in nature 50-50! Chlorine-35 makes up 75.77% of all Chlorine atoms in the universeChlorine-35 makes up 75.77% of all Chlorine atoms in the universe Chlorine-37 makes up 24.23% of all Chlorine atoms in the universeChlorine-37 makes up 24.23% of all Chlorine atoms in the universe

Electrons and atom charge If # p + = # e -If # p + = # e - Then atom is NOT CHARGEDThen atom is NOT CHARGED Charge = #p + - #e-Charge = #p + - #e- If #p > #e-If #p > #e- Then + charged (cation)Then + charged (cation) If # p < # e-If # p < # e- Then – chargedThen – charged(anion) ALL ELEMENTS ARE NEUTRAL, AND NOT CHARGED - AN ELEMENT HAS TO REACT IN ORDER TO BE CHARGED!ALL ELEMENTS ARE NEUTRAL, AND NOT CHARGED - AN ELEMENT HAS TO REACT IN ORDER TO BE CHARGED! A CHARGED ATOM IS CALLED AN IONA CHARGED ATOM IS CALLED AN ION A NEGATIVE ION IS CALLED AN ANION, AND A POSITIVE ION IS CALLED A CATIONA NEGATIVE ION IS CALLED AN ANION, AND A POSITIVE ION IS CALLED A CATION

How many p +, n, e - ?? 108 47 Ag Ag 20 Ca +2 Ca +2 41 p + = e - = n = Charge on atom…. p + = e - = n = Charge on atom…. 47 47 61 20 18 21 0 +2

Write the nuclear symbol for… An atom containing 18 e-,An atom containing 18 e-, 16 p +, and 17 n. What element is it??What element is it?? Atomic number = 16Atomic number = 16 # p + = 16# p + = 16 Element is….Element is…. SulfurSulfur Number of electrons tells us…Number of electrons tells us… There are two more electrons than protonsThere are two more electrons than protons The electrons are winning by 2!The electrons are winning by 2! Charge is -2!Charge is -2! Mass Number = #p + + #nMass Number = #p + + #n 16 p + + 17 n = mass of 3316 p + + 17 n = mass of 33 S 33 -2 16

Which of the following represent isotopes of the same element? 16 8 X 16 7 X 14 7 X 14 6 X 12 6 X Look for same atomic #: (same # of protons) 16 7 Xand 14 7 X both have 7 protons, so are isotopes of Nitrogen. 14 6 Xand 12 6 X both have 6 protons, so are isotopes of C.

Which of the following represent ions? 23 11 X +114 7 X 19 9 X -1  A charge atom is known as an ION  Positive ions are called CATIONS  Negative ions are called ANIONS  Look for any atom with charge in the upper right hand corner (with a + or -)  Charge means the atom has reacted, and now has either MORE electrons than protons, or LESS electrons than protons  Atoms with – charge have GAINED electrons  Atoms with + charge have LOST electrons

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