If Na burns when it touches water, and Cl gas is toxic and can kill you…how come we can eat NaCl (salt)?
Work Ethic • What work ethic mark would you get right now? • Is that the mark you want? • Hand in your sheet when you are done. • Pick up your Famous Chemist’s or work on them.
Electrons Atoms are happiest when they have a full outer shell, but where do they get extra electrons from? And where do the electrons they lose go?
Learning Objectives I will be able to explain how compounds and molecules form I will be able to compare and contrast ionic and covalent bonds I will be able to describe polyatomic ions
What is a bond? Chemical bond: a link between two or more atoms that holds the atoms together. Compound: a pure substance made of atoms of different elements bonded together.
Types of chemical bonds Covalent bonds: atoms share electrons. Ionic bonds: one atom takes an electron from another atom. This creates a +ve and –ve ion which are attracted to each other.
Ionic bonds • The “stealing” bond. • Atoms find other atoms with electrons they need. • Electrons are transferred. • Both atoms become ions.
Remember.. • Na has 1 valence electron, it wants to lose 1 to get a full shell • F has 7 valence electrons, it wants to gain 1 to get a full shell • F takes Na’s electron and we get F- and Na+
Test Yourself! • Draw a picture of Li and Cl bonding, use arrows to show electrons moving and include ion charges • If that is easy try Mg and O • Then find two on your own to bond!
Ions Cation: a positive ion. E.g. Li+ Anion: a negative ion. E.g. Cl-
Ionic compounds • Because one ion is negative and one ion is positive… • They are attracted to each other and form an ionic lattice. • Ionic compounds form ionic lattices.
Ionic compounds • Which elements form positive ions? • Find 5 elements with positive ion charges. • Which elements form negative ions? • Find 5 elements with negative ion charges. • What do the elements have in common?
Metal and Non-metals • Can a metal and a non-metal form an ionic bond? • Can two metals form an ionic bond? • Can two non-metals form an ionic bond?
Metals and Non-metals Ionic bonds can only form between a metal (positive) and a non-metal (negative).
Covalent bonds • The “sharing” bond. • Atoms find other atoms that have electrons they need. • Covalent bonds form between non-metals. • They share the electron and form a molecule.
Remember… Hhas 1 valence electron in shell 1, it needs 2 electrons to have a full shell. O has 6 valence electrons, it needs 8 electrons to have a full shell. H and O can share electrons so they both have a full shell!
Covalent bonds H – has 1 valence electron O- has 6 valence electrons How many Hs and Os do we need to get 8 electrons?
Chemical formulas H2O = 2 Hs and 1 O
Polyatomic Ions What does poly mean?
Polyatomic Ions Polyatomic ion: a molecular ion. A covalent molecule with a charge. Sometimes when compounds form electrons get lost or gained. Go to page 80! Write down 3 examples of polyatomic ions and where they are found.
Candy Lab! You need: • A group of 4 • A bag of gummies • Toothpicks (about 10) • A worksheet and key for everyone in the group Do not eat the candy until you are finished!
When you are done your Lab: Check Your Understanding: Page 83, # 2-7, 9-12 For homework!
Spelling and Grammar? How can we check our spelling? How can we check our grammar?
Sources • Good sources: University website, Government website… • Bad sources: Wikipedia, Yahoo answers, blogs…
Chembook! • Only 2 people per element maximum! • Sign up for an element!
Me Time! • Think of up to 3 questions you have about your interest area that you can’t just google an answer for. • Start trying to collect information that relates to your questions