3 Three Types of Subatomic Particles Protons – Positive Charge (+1)Neutrons – Neutral (no charge, 0)Electrons – Negative Charge (-1)LocationsProtons & Neutrons:Nucleus of AtomElectrons:Found in the space outside the nucleus
4 Mass of Subatomic Particles When we measure the mass of protons, neutrons and electrons, we consider RELATIVE massesThat means we compare the mass of protons and neutrons to the mass of electronsMassesProton = 1 amu (or Atomic Mass Units)Neutron = 1 amuElectron = 0 amu
5 What makes each atom different? John Dalton predicted that atoms of any element are different from the atoms of all other elementsAtoms of any given element always have the same number of PROTONSAtoms of different elements have different numbers of protons
6 Atomic Number Equals the number of protons in an atom Found on the Periodic Table of Elements
7 Number of ElectronsEach positive charge in an atom is balanced by a negative charge because atoms are neutralWhat does neutral mean?The atomic numbers gives the number of protons AND the number of electrons in a neutral atom of an element
8 Practice How many protons does Sulfur have? How many electrons does Sulfur have?
9 Additional Practice On white boards How many protons does hydrogen have?How many electrons does oxygen have?How many protons does Magnesium have?How many electrons does Neon have?How many electrons does Lithium have?
10 Mass NumberTo find the number of neutrons in an atom, you have to do some simple math…The mass number of an atom is the sum of the number of protons and neutrons in an atomProtons have a mass of one, neutrons have a mass of oneIf we add them together we can find the total massFormula for Finding # of NeutronsNumber of Neutrons = Mass Number – Atomic Number
11 Practice A carbon atom has a mass number of 14 Steps How many protons does it have?How many neutrons does it have?StepsLook on the Periodic Table Elements to find the Atomic Number of CarbonSubtract the number of protons from the mass number. This is the number of neutrons.
12 Finding Mass Number If an atom has 2 protons and 2 neutrons… What is the name of the element?How many electrons does it have in a neutral atom?What is the mass number?If an atom has 11 protons and 12 neutrons…
13 IsotopesAtoms of the same element that have different numbers of neutrons, and, therefore, different mass numbersFor exampleHow many protons does Oxygen have?Sometimes Oxygen has 9 neutrons, sometimes it has 10 neutronsWhat is the mass number of an atom of oxygen that has 9 neutrons?What is the mass number of an atom of oxygen that has 10 neutrons?
14 Identifying IsotopesElement NameOxygen - 18Mass Number
15 Practice Nitrogen – 14 Neon – 20 How many protons? What is the mass number?How many neutrons?How many electrons?Neon – 20
17 Bohr ModelLooks almost like a diagram of a solar system with planets orbiting around the SunDescribes the arrangement of electrons in atoms
18 Energy Levels or Shells (Bohr Model) Electrons move in fixed orbits around the nucleusEach electron has a certain amount of energy that determines the energy level that it is inElectrons can NOT exist between energy levels
19 Electron Cloud Model This model was an improvement on Bohr’s model Bohr assumed electrons moved like planets in a solar system, but this is actually not the caseElectron CloudVisual model of the most likely locations for electrons in an atomDescribes the POSSIBLE locations of electrons around the nucleusAt any moment in time we cannot pinpoint the location of an electron
20 Atomic OrbitalsA region of space around the nucleus where an electron is most likely to be foundEach energy level contains a certain number of atomic orbitalsEach orbital can contain a MAXIMUM of 2 electronsEach Energy has a certain number of atomic orbitals
21 Energy Levels, Orbitals & Electrons Maximum Number of Electrons Number of OrbitalsMaximum Number of Electrons124839181632
22 Creating a Model of an Atom We can use the energy level and atomic orbital information in order to create a model of an atomEach energy level can contain a certain number of electrons.