Presentation on theme: "4.1 Atomic Theory & Bonding"— Presentation transcript:
1 4.1 Atomic Theory & Bonding ATOM: smallest particle of an element, has a neutral charge.PEN = proton(s) + electron(s) + neutron(s)ELEMENT: made up of 1 type of atom (eg.oxygen O)IONS: atoms with charges (eg. oxygen is O2-)MOLECULES: groups of covalently bonded atoms (eg. oxygen molecules are O2)COMPOUNDS: are made up of at least 2 atoms bonded together.Hydrogen and oxygen are atoms/elementsH2O is a compound
2 area surrounding the nucleus Structure of an Atom:NameSymbolChargeLocationAtomic MassProtonp1+nucleus1 AMUNeutronnElectrone1–area surrounding the nucleus1/1836 (0)
3 Numbers to Remember : Protons = Atomic Number Neutrons = Mass number – Atomic number (Mass # - proton #).Neutrons + Protons = Mass #Electrons in an atom = atomic number (also proton #)Electrons in an ion = atomic number – ion charge
4 Families of the Periodic Table: Columns of elements are called groups, or familiesAll elements in a family have…similar propertiesbond with other elements in similar wayshave the same number of valence electronsFamily names (on the periodic table!):Group 1 = alkali metals (1+, highly reactive)Group 2 = alkaline earth metals (2+, reactive)Group 17 = the halogens (1-, very reactive)Group 18 = noble gases (0, unreactive)Periods are horizontal rows on the periodic table.
5 Where are the following? INCREASING REACTIVITYWhere are the following?Atomic NumberPeriodGroup/FamilyMetalsNon-metalsTransition metalsMetalloidsAlkali metalsAlkaline earth metalsHalogensNoble gases
6 Periodic Table & Ion Formation: Ions: Atoms that gain and lose electrons to become stable (full valence shells).1. Cations: metals that lose electrons & form positive ions (Na+)Multivalent: Some metals can have more than one charge (Fe2+ or Fe3+).2. Anions: Non-metals gain electrons & form negative ions (O-2)
7 Bohr Diagrams:Bohr diagrams show how many electrons appear in each electron shell around an atom. (2, 8, 8, 18, 18)Valence electrons: electrons in the outermost shell ONLY.If the valence shell is full = stableIf the valence shell is not full = reactive
8 Bohr Diagrams What element is this? It has = 18 electrons, and therefore 18 protonsIt has 8 electrons in the outer (valence) shell18 p22 nArgon!
9 Electrons are transferred from the cations to the anion Ionic Bonds:Formed between Metals (cations) & non-metals (anions).Valence electrons are transferred from metal to nonmetal.Eg. Li2OLithiumOxygen+Electrons are transferred from the cations to the anionLi+ O2- Li+Lithium oxide,Li2OCovalent Bonds:Formed between two or more non-metalsValence electrons are shared between atomsEg. HFHydrogenFluorine+Electrons are sharedHydrogen fluoride
10 Lewis Diagrams: Only valence electrons are shown Dots representing valence electrons are placed around the element symbols (on 4 sides, imagine a box around the symbol)Electron dots are placed singularly,then they are paired.Ex: Nitrogen atom
11 Lewis Diagrams for Ions: Ex. Nitrogen ionRemove or add electron dots tomake full valence shells.Square brackets and the chargeare placed around each ion2+––• •• •• •• •• •• •• •• •• •• •• •• •• •• •• •• •• •• •BeClClBeClClBeClSince Be2+ wants to donate 2 electrons and each Cl– wants to accept only one, two Cl– ions are necessaryEach beryllium has two electrons to transfer away, and each chlorine wants one more electronThe ionic compound Beryllium chloride is formed
12 Lewis Diagrams For Covalent Bonds: valence electrons are drawn to show sharing of electrons.Remember: All atoms “like” to have a full valence shellThe shared pairs (“bonding pairs”) of electrons are usually drawn as a straight line“lone pairs” are the electrons not shared