Presentation on theme: "Notes – Combining Atoms to Make Compounds Compound – a combination of two or more elements whose atoms are bonded together to form a new substance. Example:"— Presentation transcript:
Notes – Combining Atoms to Make Compounds Compound – a combination of two or more elements whose atoms are bonded together to form a new substance. Example: Sodium + chlorine produces sodium chloride. Na + Cl NaClThe arrow means “produces” or “yields”. Making compounds using Lewis structures: Sodium has one valence electron, chlorine has seven. Na +Cl------>Na Cl Sodium donates its one valence electron to chlorine to form a bond. The new substance is called sodium chloride, a compound. Now, the valence orbitals of both atoms (now ions) are full.
Many compounds are made of different atoms in different combinations. For example, sodium chloride has one atom each of sodium & chlorine. But some compounds the ratio is not 1:1. Example: Sodium and oxygen Na + O ------> Na O We still need one more electron to fill the valence orbitals, so let’s add another sodium. Na + Na O ------>Na ONa Notice how we rearranged the electrons to accommodate the second sodium on the opposite side of the oxygen. The formula for this compound is Na 2 O. The subscript 2 means there are two sodiums.
The same rules hold true for sodium phosphide. 3Na + P ------> Na P The formula for sodium phosphide is Na 3 P. (Actually the electrons are all the same; the colors are for keeping track.) Assignment: For Period 2 on the periodic table, make compounds from the following. Show the recations as in the above examples. Write their Lewis structures, formulas and names. Note: in the compound, the name for the negative ion assumes the “–ide” ending. Group one + group 17 Group one + group 16 Group one + group 15 Group one + group 14 (assume group 14 element forms a negative ion) Group 13 + group 17 Group 13 + group 15 Group two + group 17 Group two + group 16 Group two + group 14