Applied Chapter 3.2 : Structure of AtomsPresentation Transcript
Chapter 3.2 Structure of Atoms
Objective 1: Describe the evidence for the existence of electrons, protons, and neutrons, and describe the properties of these subatomic particles. Define atom: smallest particle of an element that retains the chemical properties of that element. Subatomic particles: Protons Neutrons Electrons
Discovery of the Electron Late 1800’s – J.J. Thomson discovered the electron through experiments with cathode-ray tubes. Electron Properties Relative Charge Mass Number actual mass - 1 0 9.109 x 10-31 kg Plum Pudding Model of atom
Discovery of Atomic Nucleus In 1911 – Ernest Rutherford – Gold Foil Experiment Showed that there was a small – dense positively charged nucleus of an atom. Proton Properties Relative Charge Mass Number actual mass + 1 1 1.673 x 10-27 kg
Neutrons Discovered in 1932 by James Chadwick British Scientist Neutron Properties Relative Charge Mass Number actual mass 0 1 1.675 x 10-27 kg
The Atom Nuclear Forces – Short range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together
Sizes of Atoms
Nucleus compared to rest of atom - approximately size of marble compared to a large football stadium.
Atom is mostly empty space
Objective 2 Discuss atoms of different elements in terms of their numbers of electrons, protons, and neutrons, and define the terms atomic number and mass number Atomic Number (Symbol – Z) Number of protons in nucleus of atom Determines the identity of the atom!!!!! C - 6 He - ___ F - ___ Pb - ___ Use periodic table to find these! Since atoms are neutral, atomic number is also number of electrons So C also has 6 electrons He - ____ electrons
Define isotope, and determine the number of particles in the nucleus of an atom.
All Hydrogen atoms contain 1 proton
Many naturally occurring elements can contain different numbers of neutrons.
Isotope – at0ms of the same element that have different masses.
n n n Protium 99.985 % Deuterium 0.015 % Tritium Trace Three isotopes of Hydrogen
Mass number – total number of protons and neutrons in the nucleus of an isotope
Symbol – A
Protium has 1 proton and 0 neutrons
Mass number = #p + #n
= 1 + 0
What is the mass number deuterium and tritium?
Find on periodic table
Determine the number of particles in an atom How many protons, electrons, and neutrons are present in an atom of copper whose atomic number is 29 and whose mass number is 64? How many protons and electrons are in an atom of sodium whose atomic number is 11? An atom has 13 protons and 14 neutrons. What is its mass number? Calculate the mass number for an atom that has 45 neutrons and 35 electrons.
Name of atom – mass number
Uranium - 235
A X A : mass number, Z : atomic number, X : symbol of element
Number of protons Neutrons Electrons
92 143 92
Nuclide – general term for any isotope of any element
Determine the number of particles in isotopes. Calculate the numbers of protons, electrons, and neutrons in oxygen – 17 and in oxygen – 18. Chlorine has two stable isotopes, chlorine – 35 and chlorine – 37. The atomic number of chlorine is 17. Calculate the numbers of protons, neutrons, and electrons each isotope has. Calculate the numbers of protons, electrons, and neutrons for each of the following isotopes of calcium : Ca and Ca 42 44 20 20