Chemical Bonds

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TABLE

Slide 27

Generally,

Metallic compound + nonmetallic compound  IONIC compound

Ionic compounds are generally high-melting solids that are good conductors of heat and electricity in the molten state.

Examples are NaCl, common salt, and NaF, sodium fluoride.

TABLE

Slide 28

Naming compounds

The chemical formula represents the composition of each molecule.

In writing the chemical formula, in almost all cases the element farthest to the left of the periodic table is written first.

So for example the chemical formula of a compound that contains one sulfur atom and six fluorine atoms is SF6.

If the two elements are in the same period, the symbol of the element of that is lower in the group (i.e. heavier) is written first e.g. IF3.

Slide 29

In naming covalent compounds, the name of the first element in the formula is unchanged.

The suffix “-ide” is added to the second element.

Often a prefix to the name of the second element indicates the number of the element in the compound

SF6 – sulfur hexafluoride

P4O10 – tetraphosphorous decoxide

CO – carbon monoxide

CO2 – carbon dioxide

Slide 30

The binary compounds of hydrogen are special cases. They were discovered before a convention was adopted and hence their original names have stayed

Hydrogen forms binary compounds with almost all non-metals except the noble gases.

Example

HF - hydrogen fluoride

HCl - hydrogen chloride

H2S - hydrogen sulfide

Water H2O is not called dihydrogen monoxide

Slide 31

Organic molecules (containing C) have a separate nomenclature

The molecular formulas for compounds containing C and H (called hydrocarbons) are written with C first. Example, CH4, C2H6, etc.

Slide 32

Binary ionic compounds

Compounds formed by elements on opposite sides of the periodic table which either give up (left side) or take up electrons (right side).

Depending on the atom, there can be an exchange of more than one electron resulting in charges greater than ±1.

Slide 33

Group IA – alkali metals – loose 1 e- to form +1 (Na+)

Group II A– alkaline earth metals –loose 2 e- to form +2 (Ca+2)

Group III A– loose three e- to form +3 (Al+3)

Group IV A– loose four e- to form +4 (Sn+4)

Group V A– accept three e- to form –3 (N-3)

Group VI A– accept two e- to form –2 (O-2)