Presentation on theme: "The Nonmetal-Nonmetal vs Metal – Nonmetal Bond. Lewis Dot Structures A famous chemist named Lewis invented a symbol to show valence electrons. He used."— Presentation transcript:
Lewis Dot Structures A famous chemist named Lewis invented a symbol to show valence electrons. He used a dot next to the symbol to represent each valence electron. The dots are spread around the 4 sides. Each pair of dots Represents a bond.
Covalent Bonds What is a Covalent Bond? - A covalent bond is a chemical bond resulting from SHARING of electrons between 2 nonmetals. ?
Covalent Bonds can have multiple bonds, so you should be familiar with the following… Single Covalent Bond- chemical bond resulting from sharing of an electron pair between two atoms. H2O Double Covalent Bond- chemical bond resulting from sharing of two electron pairs between two atoms. CO 2 Triple Covalent Bond- chemical bond resulting from sharing of three electron pairs between two atoms. N 2
Types of Covalent Bonds Two types of colvalent bonds: nonpolar and polar Recall electronegativity (desire for electrons) -see shaded table on ole yeller The electronegativity difference between the two atoms determines whether it is a nonpolar or polar bond. Electronegativity difference: 0.4 2.0 Nonpolar Polar Ionic
Polar Bonds A nonpolar bond tends to share electrons equally A polar bond means there is a dipole or one pole (end) with a positive charge and one pole (end) with a negative charge, therefore they tend to stick together better since their opposite charges attract. (=)(-) Very strong polar bonds are ionic bonds like NaCl
Covalent Bonds Do NOT have ions or need to Balance Charges They use prefixes to show the number of atoms: Mono- Di- Tri- Tetra- Examples: H 2 O = dihydrogen monoxide CO 2 = carbon dioxide dinitrogen tetraoxide = N 2 O 4 Phosphorus trichloride = PCl 3
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When a metal and nonmetal come together, a pair of electrons acts as a bond and they each become ions.
Ionic Bonding Rules: Metal first, nonmetal second Nonmetal ion becomes ‘ide’ Metal is positive, nonmetal is negative Charges must balance to zero Formula uses a subscript to balance charges Example: MgCl 2 ; Na 2 O; NaCl
The sodium atom and chloride atom bond together as ions and form a new compound.
Practice: Sodium and fluorine Barium and iodine lithium and phosphorus Aluminum and oxygen Beryllium and oxygen Calcium and nitrogen
Answers: Sodium and fluorine sodium fluoride NaF Barium and iodine barium iodide BaI 2 lithium and phosphorus lithium phosphide Li 3 P Aluminum and oxygen aluminum oxide Al 2 O 3 Beryllium and sulfur beryllium sulfide BeS Calcium and nitrogen calcium nitride Ca 3 N 2
Solutions When ionic compounds are put in water, they dissolve into ions:
Polyatomic ions: are groups of atoms bonded together with a charge hence the name “poly” “atomic” “ions”. Examples: OH -1 = hydroxide NO 3 -1 = nitrate PO 4 -3 = phosphate SO 4 -2 = sulfate *They behave just like single atom ions.
Practice: Use polyatomic ions just like any other ion; But when you have more than one, use parentheses. barium hydroxide= (Notice parentheses show multiple ions.)
potassium sulfate = K SO 4 +1 -2 potassium sulfate = K 2 SO 4 +1(2) + -2 = 0
Transition metals: Metals that have more than one possible charge: Cobalt: Co +2, Co +3 Copper: Cu +, Cu +2 Iron: Fe +2, Fe +3 Lead: Pb +2, Pb +4 When writing the names, always use roman numerals to show the charge.
Examples: Cobalt (II) Co +2, Cobalt (III) Co +3 Copper(I), Cu +, or Copper (II), Cu +2 Iron(II) Fe +2, or iron (III), Fe +3 Lead(II), Pb +2, or lead (IV), Pb +4 Each different charged ion behaves completely different than the other! The charges matter!
Hydrates Some ionic compounds absorb water molecules into their structures. These are called hydrates. NaCl2H 2 O is the symbol for sodium chloride dihydrate. Notice the prefix di- means 2 water molecules. Name these hydrates: MgSO 4 5H 2 O CuCl 2 4H 2 O
Finding Percentage of Water in a Hydrate You can find the percentage of water in a hydrate by dividing the mass of the water by the total mass times 100. Lets take NaCl2H 2 O Using the periodic table, the mass of Na=23, Cl=35.5, H2O = 18. Total mass with 2 H 2 0 is 94.4 Water mass (36)/ Total (94.4) x 100 = 38 % water
What are the differences between ionic bonding and covalent bonding? List them below:
Differences: Ionic Metal, nonmetal-ide Balance charges using subscripts Polyatomic ions use parentheses in multiples Transition metals use roman numerals to show charge
Differences: Covalent Two nonmetals Nonmetal, nonmetal- ide No ions- they share e- Use prefixes Don’t need to balance
Differences: Ionic Metal, nonmetal-ide Balance charges using subscripts Polyatomic ions use parentheses in multiples Transition metals use roman numerals to show charge Covalent Two nonmetals Nonmetal, nonmetal- ide No ions- they share e- Use prefixes Don’t need to balance