The Atom and Periodic Table Physical Science

Element verse Atom ATOM ELEMENT Smallest particle of an element A substance that cannot be broken down into simpler substances Ex: Neon, Gold, Helium ATOM Smallest particle of an element Counting unit of elements

History of the Atomic Model Democritus --believed in the atom J.J. Thomson --found the electron John Dalton --made the theory on atoms Ernest Rutherford --found the nucleus

History of the Atomic Model Neil Bohr --established energy levels Electron Cloud Model --the current model of the atom

3 Subatomic Particles Atoms can be broken into: Electrons Negatively charged Symbol = e- Extremely small mass Protons Positively charged Symbol = p+ Mass = 1 Neutrons No charged (neutral) Symbol = n Mass = 1

Parts of an Atom Nucleus Energy Levels/Shells/Orbitals Center of the atom Small, dense, positively charged Where Protons and Neutrons remain Energy Levels/Shells/Orbitals Around the nucleus Contains the electrons

Atomic Number The Identify of the element Number of Protons Top of the Element Block SECRET: Also the number of electrons

Mass Number The sum of the Protons and Neutrons Bottom Number of the element block Round to the Nearest Whole Number

Understanding an Element Block ATOMIC NUMBER 10 Ne Element Symbol 1st letter is upper case 2nd letter is lower case NEON Element Name 20.18 Mass NUMBER

How do you Find Items Number of Protons = Atomic Number Number of Electrons = Number of Protons (Because Atoms are neutral which means positive equals negative) Number of Neutrons = Mass Number subtract Atomic Number

Electron, Protons, Neutrons Example Practice Name Symbol Atomic Number Mass Number Number of Protons Number of Electrons Number of Neutrons NEON BORON

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ISOTOPES Atoms of the same element that have the same atomic number but different mass numbers # of protons stays the same # of neutrons change

How Isotopes are Written Elements name/symbol dash mass number Ex: Oxygen—16 p+= n = Oxygen—17 p+= n = O—18 p+= n =

Why is Mass Number a Decimal? Mass Number is the weighted average of all the isotopes of an atom The isotope whom mass number is closest to the actual mass number is more abundant

IONS Charged Particles Negative Charge = gains electrons Positive Charge = lose electrons

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The Periodic Table An arrangement of elements in columns based on properties that repeat from row to row Modern Periodic Table arranged by Henry Moseley Arranged by increasing atomic number

Parts of the Periodic Table ROWS Called Periods Go across COLUMNS Called Groups Go up and down

Periods 7 periods Elements in the same period have: Same number of energy levels or shells or orbitals

Groups 18 groups Elements in the same group have the same: Properties Valence Electrons Oxidation Numbers

Valence Electrons Code: Number of electrons on the outermost (last) energy level Code: 1, 2, 3, 4, 5, 6, 7, 8 Number next to “A” at the top of the column

Know Your Roman Numerals I = 1 II = 2 III = 3 IV = 4 V = 5 VI = 6 VII = 7 VIII = 8

Oxidation Number Number of electrons an atom will gain or lose to become stable Stable = 8 electrons on last shell Code: +1, +2, +3, ±4, -3, -2, -1, 0 “+” means lose electrons “—” means gain electrons

Labeling the Periodic Table

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Bohr’s Model Focuses On Electrons Places electrons into energy levels Developed by Neil Bohr

Components of Bohr’s Model Circles DOTS Number of Circles = Period Number = Number of Energy Level Go on the Last Circle Number of Dots = Number of Valence Electrons Important Note First energy level has a max of 2 electrons All other energy levels have a max of 8 electrons

Steps to Draw Bohr’s Model Place a dot to be Nucleus Place circles around Nucleus Place dots on last circle in correct order EXAMPLE Oxygen

Bohr Model Practice NEON Boron Helium

Electron Dot Diagrams Model of an atom in which each dot represents the valence electrons AKA: Lewis Dot Diagrams

Steps to Draw Dot Diagrams Identify the number of valence electrons Write the element’s symbol Place dots around the symbol equal to valence electrons in correct order Example NEON

Dot Diagram Practice Fluorine Sodium Carbon

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Classifying Elements Elements are classified as metals, nonmetals, or metalloids based on properties and location on the periodic table

Metals Most elements are them Malleable: hammer into sheets Good Conductors of electricity/heat Solid at room temperature (except Mercury) Ductile: turn into thin wire Luster: reflect light Malleable: hammer into sheets High Melting Point Left side of the stair step Francium: Most reactive metal High Boiling Point

Nonmetals Dull Brittle Poor Conductors of electricity/heat Most are gas at room temperature Low Melting Point Low Boiling Point Right Side of Stair Step Fluorine: most reactive nonmetal

Metalloids Have BOTH characteristics of metals and nonmetals Found on the stair-step line What are the Metalloids B, Si, Ge, As, Sb, Te, Po, At

Periodic Trend Reactivity As you go left to right across a period, the less reactive elements become

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THE FAMILIES AND GROUPS OF THE PERIODIC TABLE

Alkali Metals Group IA 1 valence electron Reactivity increases from top to bottom Francium is most reactive metal

Alkaline Earth Metals Group IIA 2 valence electrons Ca: is in your bones, teeth, shells

Transitional Metals THE MIDDLE OF THE PERIODIC TABLE Groups 3B-12B Vary in oxidation numbers Brightly colored Likes to combine with Oxygen

BORON FAMILY Group IIIA 3 valence electrons Al: most abundant metal in Earth’s crust

Carbon Family Group IVA 4 valence electrons Carbon is the element of life

Nitrogen Family Group VA 5 valence electrons N is 78% of air Main component of fertilizer

Oxygen Family Group VIA 6 valence electrons O: most abundant element in Earth’s crust

The Halogens Group VIIA 7 valence electrons Salt formers Reactive with metals Fluorine: most reactive nonmetal

Noble Gases Group VIIIA 8 valence electrons Stable = not reactive Inert Gases All Shells are full

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