Ionic Bonding What makes an atom most stable

Ionic Bonding

What makes an atom most stable? n Electron configuration – n When the highest occupied energy level is filled with electrons the atom is stable, and probably will not react chemically

Electron Dot Diagrams (Lewis Structures) n n Show valence electrons only Easy way to see if an atom is stable, and how it may react to transfer electrons

OCTET RULE n n Elements become happy when they have a complete outer shell. They are usually happy when the closest outer shell has 8 or 2 in the case of Helium. In order to do this they will either lose or gain electrons.

Ion formation n If an atom has greater than 4 valences electrons Will gain enough to make 8 (octet rule) n Becomes negatively charged ion (anion) n This applies to elements in groups 5, 6, and 7 P S Cl N F Br n

Ion formation n If an atom has less than 4 valence electrons: n n It will lose those outer electrons Becomes positively charged (cation) This applies to elements in Groups 1, 2, and 3 Write the symbol and charge of the following. Ca Na K Li Al B

Ionic bonds n n Once positive or negative ions are formed, they are attracted to each other They form a chemical bond known as an ionic bond – the force that holds cations and anions together; results from transferred electrons

Oxidation Number vs. Subscripts Ionic bonding is when two ions of opposite charge attract and bond to each other forming an ionic compound. Consider the following examples of formulas for ionic compounds. n One Na+ (sodium ion)(METAL) and one Cl(chloride ion)(Non-metal) bond to make Na. Cl (sodium chloride) n One Mg 2+ (magnesium ion) and two F (fluoride ions) bond to make Mg. F 2 (magnesium fluoride) The number at the top is the oxidation number. Once they combine you have a subscript that tells how many of each type of atom are present. Mg 3 N 2 n

Ionic Compounds Ionic bonds form between a metal and a non-metal -dissolve easily in water In solution, ionic compounds easily dissolve. -tend to form crystals with high melting temperatures.

IONIC COMPOUND NAMING n n n Compounds that contain ions. Written using chemical formulas Rules are:

STEP 1 n STATE THE CATION FIRST (THE NAME OF THE FIRST ELEMENT) METALS STEP 2 n DROP THE ENDING OF THE NAME OF THE ANION (THE SECOND ELEMENT LISTED) AND ADD “IDE NON-METALS