Chemical Bonding

Bellwork When a nail rusts, is that a chemical change or a physical change? Explain.

Objectives Students should be able to Distinguish between ionic and covalent bonds Identify when elements will form ionic or covalent bonds Distinguish between compounds and molecules

Chemical Bonding Compounds Two types of chemical bonds atoms of two or more elements joined together by chemical bonds Two types of chemical bonds Ionic Bonds- one atom transfers an electron to another atom Covalent Bonds- two atoms share electrons

Ionic Bonding transfer of electrons Why? Each atom becomes more stable (full outer shell) Atom that loses an electron have only 1 or 2 valence electrons Atom that gains an electron have 7 electrons in valence shell Ions Atoms that gain or lose electrons Ex. NaCl

Covalent Bonding share electrons Why? Atoms share electrons to become stable to fill their outer shells The number of bonds that form equals the # of electrons needed to fill outer shell Ex. H2, O2, N2

Chemical Bonding

Notetaker Practice Use a Venn Diagram to compare and contrast ionic bonds and covalent bonds.

Notetaker Practice Examples we work together: How many covalent bonds are formed in H2? In N2? Now your try it: How many covalent bonds are formed between oxygen atoms in O2?

Molecule Molecule two or more atoms joined by covalent bonds How is a molecule different than a compound? Write answer on your notetaker. Can NaCl be a molecule? Explain why or why not on your notetaker.

Notetaker Practice Explain the difference between a compound and a molecule

Chemical Reaction Process where Ex. 2H2 + O2  H2O atoms rearrange and form new bonds Ex. 2H2 + O2  H2O different from a physical change

Chemical Change vs Physical Change Examples Rust on a Chain : O2 + Fe  Fe2O3 chemical reaction because bonds break and re-form Boiling Water : H2O(liq) + heat  H2O(gas) not a chemical reaction, no rearranged bonds physical change

Thumbs up Chemical Change / Thumbs down Physical Change ? Thumbs up Chemical Change / Thumbs down Physical Change You Cut the Grass You combust gasoline in your car You digest the protein in your hamburger You dissolve sugar in water You dissolve Alka-Seltzer in water 1. Hand signals: thumbs up or thumbs down to indicate agreement or disagreement use fingers to indicate a number selection such as “Which is the correct solution one, two or three?” teacher gives feedback to the students 14 14

Notetaker Practice Explain, in your own words, what happens during a chemical reaction.