Binary compounds Chapter 6 part I

Chemical Formulas Chemical formulas inform as to the type of elements that make up the compound and in what ratios. Chemical formulas inform as to the type of elements that make up the compound and in what ratios. Chemical formulas describe both ionic compounds and molecules. Chemical formulas describe both ionic compounds and molecules. Example: H 2 O: 2 hydrogens for every 1 oxygen This is a molecule. CaCl 2 : 2 chlorines for each calcium. This is an ionic compound.

Molecular formulas Molecular formulas have 2 nonmetals bound together. Molecular formulas have 2 nonmetals bound together. Molecules are held together by sharing electrons, not by charge. Molecules are held together by sharing electrons, not by charge. Hydrogen is a nonmetal!! Hydrogen is a nonmetal!!

Formula Units Chemical formulas for ionic compounds are called formula units. Each unit is part of a larger structure. Consist of a metal and a nonmetal. They are held together by charge.

Ions and valence electrons To write chemical formulas one needs to understand how these elements combine. To write chemical formulas one needs to understand how these elements combine. Electrons are the key! Electrons are the key! Valence electrons (outer shell electrons) may be determined by the group on the periodic table. Valence electrons (outer shell electrons) may be determined by the group on the periodic table.

Lewis dot The number of valence electrons is represented by dots outside the atomic symbol. Hydrogen has one valence electron and therefore one dot. Lithium has one valence electron and therefore one dot Berylium would have two dots and so on. These are the same numbers as found in the representative elements.

Lewis Dot Practice Lewis Dot on your worksheet. What happens to the number of dots if the element forms an ion?

Ionic compounds and Lewis Dot When Ions lose an electron they have a complete shell, but they have a charge. When Ions lose an electron they have a complete shell, but they have a charge. These charged ions are attracted to the opposite charge forming salts. These charged ions are attracted to the opposite charge forming salts.

Molecular Bonding and Lewis Dot Except for H and He, how many electrons do the elements in a molecule want around them? Except for H and He, how many electrons do the elements in a molecule want around them? s 2 p 6 8 electrons to mimic the noble gases. s 2 p 6 8 electrons to mimic the noble gases. This is called the octet rule. Octet=8 This is called the octet rule. Octet=8

Bonding and Lewis Dot Double bonds and single bonds are also represented by Lewis dot. Try bonding on your worksheet.