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A Little Periodic Table History… History of the Periodic Table • Dmitri Mendeleev, a Russian scientist born in Siberia in 1834, is known as the father of the periodic table of the elements • The periodic table is designed to help you predict chemical and physical properties of elements Method Behind the Madness • Mendeleev set out to find a pattern in the elements • He wrote facts on paper cards for each element Melting Point Density Colors Atomic Masses Method Behind the Madness (cont) • After laying all of his cards out he noticed that by arranging them according to their properties they were arranged in order of increasing atomic mass • Mendeleev was even able to use the patterns in his table to predict the properties of undiscovered elements • The first periodic table was published in 1869 The Genious of Mendeleev's Periodic Table - TedEd Mendeleev Song Today, elements are arranged in order of increasing atomic number on the periodic table Big Science Idea Element Location Elements are located in three main categories on the periodic table based on their physical properties Metals Nonmetals Metalloids Physical Properties Physical Property - a property of matter that can be observed or measured WITHOUT CHANGING the substance Examples of Physical Properties Mass – How much matter is in an object Malleable – Can be pounded/rolled into a shape Density – How tightly mass is packed into an object Color/Texture Ductile – Can be stretched into a long wire Metals, Nonmetals, & Metalloids Metals Most elements are metals. The 88 elements to the left of the stair-step line are metals or metal-like elements. Physical Properties of Metals: high luster (shininess) good conductors of heat and electricity high density (heavy for their size) high melting point ductile malleable Metals Non-Metals Non-metals are found to the right of the stair-step line. Their characteristics are opposite those of metals. Physical Properties of Nonmetals: no luster (dull appearance) poor conductor of heat and electricity brittle (breaks easily) not ductile not malleable low density low melting point Non-Metals Metalloids Elements on both sides of the zigzag line have properties of both metals and nonmetals. These elements are called metalloids. Physical Properties of Metalloids: solids can be shiny or dull ductile malleable Antimony (Sb) conduct heat and electricity, but not as well as metals Metalloids Scientists organize elements according to their physical and chemical properties Big Science Idea How to Read the Periodic Table • The Periodic table is designed to help you predict what an element's physical and chemical properties are • You can also predict what elements will bond with each other Elements are arranged: Vertically into Groups (also called Families) Periodic Table Bitesize (only show part 1) Horizontally Into Periods Periodic Table Arrangement Groups or Families • Vertical columns on the periodic table Periods • Horizontal rows of the periodic table Why? If you looked at one atom of every element in a group you would see… Each atom has the same number of valence electrons (the electrons in its outermost shell). Think back to the Bohr Model An example… The group 2 atoms all have 2 electrons in their outer shells Be (Beryllium) Atom Mg (Magnesium) Atom Valence Electrons • Effect the way an atom bonds, which determines many of the chemical properties of the element o Atoms can have anywhere between 1 and 8 valence electrons • This is why elements within a group usually have similar chemical properties Chemical Properties A chemical property is a characteristic that is observed when a substance changes into a different substance Examples of Chemical Properties Combustible – capable of igniting at higher temps Corrosion Reactivity Oxidation – rusting or tarnishing Flammable – capable of igniting Metals – Reactivity Reactivity decreases from left to right Metal Reactivity Nonmetals – Reactivity Reactivity increases from left to right Not Reactive If you looked at an atom from each element in a period you would see… Each atom has the same number of electron holding shells. An example… The period 4 atoms each have 4 electron containing shells 4th Shell K (Potassium) Kr (Krypton) Atom Atom Fe (Iron) Atom Each group has distinct properties The periodic Table is divided into several groups based on the properties of different atoms For example… The periodic table tells us several things… Periodic Table Information on the periodic table: •Atomic number •Atomic symbol •Mass number (Atomic Mass) •Element name •Group and period numbers Think Inside the Box Atomic Number: Number of protons (also the number of electrons) in an atom of an element. Element’s Symbol: An abbreviation for the element. Element’s Name Atomic Mass: Number of protons + neutrons. 8 O Oxygen 16 Chemical Symbols • Shorthand way of representing the elements • Usually one or two letters • Usually taken from the name of the element – Carbon-C, Calcium-Ca, Hydrogen-H, IodineI, Oxygen-O, Chlorine-Cl Chemical Symbols • Some symbols come from their Latin name: – – – – Gold-Au--aurum Silver-Ag--argentum Iron-Fe--Ferrum Mercury-Hg--hydrogyrum How do we know the number of subatomic particles in an atom? • Atomic number: this number indicates the number of protons in an atom of a particular element – Ex: Hydrogen’s atomic number is 1 • So hydrogen has 1 proton – Ex: Carbon’s atomic number is 6 • So carbon has 6 protons **The number of protons is a unique property that identifies an element. Ex. 2 protons = He, 29 protons = Cu Atomic Mass • Atomic Mass Unit (amu) is used to measure the particles in atoms – Protons & Neutrons are about 1 amu – Electrons are MUCH smaller • It takes about 2,000 electrons to equal 1 amu • Atomic Mass = Protons + Neutrons Atomic # Symbol Mass # Pick an element off the Periodic Table and draw and label it just like this one! Group and Period Numbers Period Numbers Group Numbers How Can I Find Out the Number of Protons and Electrons? Atomic No. = # of protons Since protons & electrons are EQUAL...the atomic no. also tells you the # of electrons *Atomic # = # of Protons = # of electrons* Let’s take a look: A = Atomic number P = Number of protons E = Number of electrons These are all the same number!! So Atomic # = # of Protons = # of electrons Then How Can I Find Out the Number of Neutrons? Mass Number = number of protons + number of neutrons So Neutrons = Mass Number – Atomic Number Now let’s look at MAN: M= Atomic Mass - A= Atomic Number N= # of Neutrons Simple math! Mass minus atomic number gives you the number of neutrons!!! Let’s work a couple together Let’s try Nitrogen! Nitrogen A= 7 P= 7 E= 7 M= 14 -A= 7 N= 7 Boron A= 5 P= 5 E= 5 M= 11 -A= 5 N= 6 Now that we know how to figure out protons, electrons, and neutrons… Let’s try to create a Bohr Model Lithium Atomic Structure Electrons = 3 (2 in the 1st shell, 1 in the 2nd shell) + 3 Li Lithium 7 + Protons = 3 + - - Neutrons = 4 (7-3 = 4) Protons determine an element’s identity and valence electrons determine its chemical properties Big Science Idea SUMMARY 1. The Atomic Number of an atom = number of protons in the nucleus. 2. The Atomic Mass of an atom = number of Protons + Neutrons in the nucleus. 3. The number of Protons = Number of Electrons. 4. Electrons orbit the nucleus in shells. 5. Each shell can only carry a set number of electrons.