Chapter 20 Section 2

Types of bonds A neutral atom is one that has an equal number of protons and electrons. Ion—a charged particle (atom) that has more or fewer electrons than protons The positive and negative charges are not equal When an atom gains or loses electrons, it becomes charged; an ion Superscript is the number that shows the charge on the ion.

Ionic bond Ionic bond—force of attraction between the opposite charges of the ions in an ionic compound. In an ionic bond, a transfer of electrons takes place. This means one atom loses electrons and another atom gains electrons before they bond. These atoms are attracted to each other like little magnets. The opposite charges attracts them to each other to from compounds.

After all the electrons are lost or gained, the over all charge of the compound is 0. All the pluses = the minuses so the compound is neutral.

Characteristics of ionic compounds Ionic bonds usually are formed between a metal and a nonmetal Ionic compounds are often crystalline solids with high melting points The smallest unit of an ionic compound is an ion They tend to form brittle solids Metals give up electrons and nonmetals take on electrons.

Covalent Bond Covalent bond– the force of attraction between atoms when they share electrons. Co: means together valent: means valence electron Some atoms become more stable by sharing electrons because it takes too much energy to gain or loose the electron. A single bonds = 1 shared electron A double bond = 2 shared electrons A triple bond = 3 shared electrons

Characteristic of covalent bonds The electron actually spends time around each atom Covalent compounds from between non metals Many covalent compounds are gases or liquids at room temp. The smallest unit of a covalent compound is called a molecule Molecule—neutral particle that forms as the result of electron sharing ex: water, nitrogen, hydrochloric acid

Polar covalent molecule A covalent molecule has a slightly postive end and a slightly negative end although the over all molecule is neutral There is an unequal sharing of electrons because the atoms in the molecule have different sizes Water is a polar molecule

Nonpolar covalent molecule A molecule in which the electrons are shared equally. These are molecules made from two identical atoms or molecules that are symmetric Ex. CCl4