5 Protons (+) Neutron (0) Valence electrons Electron (-) P+ N A simplified slideNeutron (0)
6 Atomic Structure and the Periodic Table (cont) Electrons (negative) move around the nucleus in the electron cloud. The electron cloud has different energy shells (or orbits). In a neutral atom the number of electrons equals the number of protons.
8 Atomic Structure and the Periodic Table (cont) Valence electrons are the electrons in the outer shell.The valence electrons determine which elements combine to form compounds!
9 Why do Elements Form Compounds? 1. Atoms combine to complete the outer energy shell of electrons2. A complete outer energy shell is stable. (atoms with filled outer energy shells won’t combine with other atoms)
10 Why do Elements Form Compounds? 3. shell #1 it is complete with 2 electrons.4. Shells # 2-7 are “complete” with 8 electrons
12 What happens when a chemical bond is formed? A chemical bond is the force of attraction that holds atoms togetherA new substance is formed in a chemical reactionproperties of the new substance are different than the properties of the elements that make them upElectrons are gained, given away or shared
13 Electron Dot Diagrams Shows valence electrons only Uses dots to represent electronsCan be used to show how elements bond
14 Chemical FormulaChemical Formula - A shorthand way to write the name of the compoundWhat information does a chemical formula contain?
15 MetalsMETALS are on the left side of the Periodic Table. They have a low number of valence electrons and can easily give them to other atoms.Almost empty shells
16 NonmetalsB. NONMETALS are on the right side of the Periodic Table. They have a high number of valence electrons and can easily take or share valence electrons from other atomsAlmost full shells
17 Semi MetalsC. SEMIMETALS are found between metals and nonmetals along the zigzag line. They can either lose or share valence electrons with other atomsAbout half full shell
19 Ionic BondsION- a charged particle; atoms either gain or lose electrons to form:A. Positive Ions form when atoms lose electrons (more protons than electrons)B. Negative Ions form when atoms gain electrons (more electrons than protons)
20 Ionic Bonds Metal to nonmetal Transfer of electrons from one atom to the other
27 Covalent bondsForm nonmetal to nonmetalShared electrons
28 How does a covalent bond form? atoms share electrons to fill outer energy shells (it takes too much energy to transfer electrons)the force that holds atoms together in a covalent bond is the attraction of each atom’s nucleus for the shared pair of electrons
29 Properties of covalent compounds Weak bondslow melting & boiling pointsMany are gases and liquidscannot conduct electricity when dissolved in water
30 moleculea neutral group of atoms held together by a covalent bond; smallest piece of a compoundCovalent compounds are also called molecular compounds
36 Metallic Bondsmetal to metalPositive metal ions “swimming” in sea of released electrons
37 How does a metallic bond form? Metals tend to lose electrons and form positive ions.The bonds are held together by the force of attraction between positive metal ions and the many electrons surrounding them.
38 Metallic bondmetal atoms combine in regular patterns which allow the electrons to move from atom to atom
39 Alloy mixture of 2 or more elements, at least 1 is a metal stronger and less reactive than pure metals.Properties of alloys are different from the pure metals that make them up
40 Metallic bond: mixture or chemical bond (honors slide) Alloys are a mixture because they can be in any ratioAlloys are like a chemical bond because they have different properties than the metals that form themAlloys are like a chemical bond because the electrons are interacting
41 Properties of Metals Dense shiny Solids at room temperature (except Mercury)malleableductileGood conductors of heat and electricity