Presentation on theme: "Properties of Atoms and the Periodic Table"— Presentation transcript:
1 Properties of Atoms and the Periodic Table Chapter 18Properties of Atoms and the Periodic Table
2 Scientific ShorthandScientists use abbreviations to write the name of elements.Abbreviations are easier to write than the whole element.For example:Carbon is written asAluminum is written asSilver is written asCAlAg
3 Scientific ShorthandThe first letter in the symbol is ALWAYS written with a capital letter.If there is a second letter, it is ALWAYS written as a lowercase letter.Some element symbols are based on their English names, while others are based on their Latin names.Silver is Ag from its Latin name Argentum.
4 Atoms Elements are made of atoms Atoms are the smallest piece of matter that still retains the properties of the element.
5 Subatomic Particles Each atom is made up of smaller particles. In the center of the atom is the nucleus.The nucleus is made of protons and neutrons.
6 Subatomic Particles Each atom is made up of smaller particles. Electrons orbit around the nucleus
7 Subatomic Particles Properties of Protons Properties of Neutrons Electrical charge of +1Mass =1 amu.Properties of NeutronsElectrical charge of 0.Properties of ElectronsElectrical charge of -1Mass is approximately 1/1800 of a proton.
8 QuarksProtons, neutrons and electrons are all made up of even smaller particles called quarks.
9 QuarksTo study quarks, scientists smash atoms together to break the protons apart.
10 QuarksBased on the data collected, they can reconstruct the structure of the atom.
11 The Atomic Model - History Democritus (400 B.C.)First proposed that atoms made up all substances.AristotleBelieved that matter is uniform throughout.This idea lasted for about 2,000 years.
12 The Atomic Model - History Dalton’s ModelEach atom was a solid sphere.Allowed scientists to explain how chemical reactions occurred.Thomson, Rutherford, and BohrEach scientist’s experiments helped to identity different parts of the atom and the structure of the atom.
14 Electron Cloud Model The most current model of the atom. The electron cloud is 100,000 times larger than the diameter of the nucleus, but each electron is smaller than the proton.Electrons are so small, and moving so fast, that they are difficult to find.
15 What holds the Nucleus Together? Protons in the nucleus bothrepel and attract each other.The repulsions are due toelectromagnetic force andthe attractions are due to thestrong nuclear force. Thestrong nuclear force onlyacts over very shortdistances, about the size ofan atomic nucleus. Neutronsand protons also attract eachother because of the strongnuclear force.
16 Atomic Masses Most of the mass of an atom is within the nucleus. Protons and neutrons each weigh about x kg.That’s kg!Electrons are 1/1800 of the mass of a proton or neutron.
17 Atomic MassesTo measure atomic mass, we use the “atomic mass unit” or amu.Mass of 1 proton = 1 amuMass of 1 neutron = 1 amu
18 Atomic Number The number of protons in an atom identify the element. Each element has a different number of protons.Atoms with 8 protons are always oxygen.Atoms with 6 protons are always carbon.Atoms with 16 protons are always sulfur.The number of protons in an atom is called the atomic number.
19 Atomic Number Practice Use your periodic table to find the atomic number of the following elements:Aluminum (Al)Titanium (Ti)Tin (Sn)Osmium (Os)Erbium (Er)How many protons does each atom have?The number of protons are equal to the atomic number.Al = 13Ti = 22Sn = 50Os = 76Er = 68
20 Mass NumberThe mass number of an atom is the sum of the number of protons and neutrons in the nucleus.ElementProtonsNeutronsMass NumberBoron56CarbonOxygen8Sodium1112Copper29345+6116+6128+81611+122329+3463
21 Using the Atomic Number & Mass Number If you know the atomic number and mass number, you can determine the number of neutrons.Mass Number- Atomic NumberNumber of Neutrons
22 PracticeDetermine the number of protons and neutrons in the following atoms:Lithium – Atomic Number = 3Mass Number = 7Argon – Atomic Number = 18Mass Number = 39Strontium – Atomic Number = 38Mass Number = 88
23 AnswersDetermine the number of protons and neutrons in the following atoms:Lithium – Protons = 3Neutrons = 7 – 3 = 4Argon – Protons = 18Neutrons = 39 – 18 = 21Strontium – Protons = 38Neutrons = 88 – 38 = 50
24 IsotopesAtoms of one type of element must have the same number of protons.However, they can have different numbers of neutrons.Atoms with the same number of protons and different numbers of neutrons are called isotopes.
25 Isotopes Examples Carbon-12 has a mass of 12 amu. All carbon atoms must have 6 protons.Neutrons = 12 – 6 = 6.C-12 has 6 protons and 6 neutrons.Carbon-14 has a mass of 14 amu.Neutrons = 14 – 6 = 8.C-14 has 6 protons and 8 neutrons.
26 Isotopes Examples Uranium-235 has a mass of 235 amu. All uranium atoms must have 92 protons.Neutrons = 235 – 92 = 143.U-235 has 92 protons and 143 neutrons.Uranium-238 has a mass of 238 amu.Neutrons = 238 – 92 = 146.U-238 has 92 protons and 146 neutrons.
27 Average Atomic MassBecause atoms can have different numbers of neutrons, the mass numbers can be different.To get an overall mass of one element, we take the weighted-average of all the isotopes and determine the average atomic mass for the element.
28 Neutral Atoms In the nucleus, which particles have charge? ProtonsWhat charge do they have?PositiveWhat particle is opposite that charge?Electrons
29 Neutral AtomsTo balance the charges in the atom, the number of protons must equal the number of electrons.Li has 3 protons, so the nucleus has a charge of +3.To balance that charge, there must be 3 electrons that add up to -3.Overall, the charge is (+3) + (-3) = 0, so the atom is neutral.
30 Practice Determine how many electrons the following atoms have: Magnesium, Protons = 12Beryllium, Protons = 4Nitrogen, Atomic Number = 7Bromine, Atomic Number = 3512 Electrons4 Electrons7 Electrons35 Electrons
32 Practice Iodine I 53 127 74 Mercury Hg 80 201 121 Neon Ne 10 20 Mg 12 ElementSymbolAtomic NumberMass NumberProtonsNeutronsElectronsIodineI5312774MercuryHg80201121NeonNe1020MagnesiumMg1224RubidiumRb378548NiobiumNb419251RheniumRe75186111
33 Bohr Models of the Atoms Each atom had orbitals or shells in which the electrons can fit.1st Shell: up to 2 electrons can fit2nd Shell: up to 8 electrons can fit3rd Shell: up to 18 electrons can fit4th Shell: up to 32 electrons can fitMust start with the smallest/closest orbital or shell first.
34 Drawing Bohr Models Hydrogen Boron AN = 1 AM = 1 e- = 1 AN = 5 AM = 11 1 p+, 0 noAN = 1AM = 1e- = 15 p+, 6 noBoronAN = 5AM = 11e- = 5
36 Electron Dot Diagrams Write the symbol of the element Determine the number of valence electrons (electrons in the outermost energy level)Start placing valence electrons around the symbolPair electrons only after all four sides (top, bottom, left, right) have been used once
37 H H H H Example: Hydrogen Hydrogen has 1 valence electron Chose one side, and place the electronHHHHOROROR
38 Cl Example: Chlorine Chlorine has 7 valence electrons Place one on each side firstThen begin to pair the remaining electronsCl
39 N Example: Nitrogen Nitrogen has 5 valence electrons Place one on each side firstThen begin to pair the remaining electronsN
40 Be Example: Beryllium Beryllium has 2 valence electrons Place each electron on different sidesBe
41 He Example: Helium Helium has 2 valence electrons Helium is an EXCEPTIONPair the two electrons because the energy level can only 2 electronsHe
42 Periodic LawScientists Julius Lothar Meyer and Dmitri Mendeleev individually produced classification schemes for elements in 1869.Periodic Law: When elements are arranged in order of increasing atomic numbers, elements with similar chemical properties will occur at regular (periodic) intervals.
43 Periodic TableThe rows on the periodic table are separated into periods.
44 Periodic TableAs chemists worked on determining which substances were elements, they noticed that some elements acted very much like other elements. For example, one atom of some metals always reacts with two atoms of oxygen. Chemists called these similar elements a group of elements.
46 Regions of the Periodic Table Metals: Elements to the lower left side of the periodic table.Nonmetals: Elements to the upper right of the periodic table.Metalloids: Elements in between the metals and nonmetals.