Chapter 11 Notes

Electron Levels

(K) first level - 2 electrons (L) second level - 8 electrons (M) third level - 18 electrons (N) fourth level - 32 electrons

Chemical Bond

A chemical bond is a force that holds two or more atoms together. The outermost electrons can easily be attracted to the nucleus of other atoms. This is what causes a chemical bond.

Covalent Bond

A covalent bond is a chemical bond formed when two atoms share one or more pairs of valence electrons. The atoms then form a stable covalent compound.

Double Covalent Bonds

A double covalent bond exists when two atoms share two pairs of valence electrons. Double bonds are stronger than single bonds.

Metallic Bond- Electron Pooling

A metallic bond is a bond formed when many metal atoms share their pooled valence electrons. Valence electrons in metals are not bonded to one atom; instead a "sea of electrons" surrounds the positive ions.

Polar Molecule Definition

A molecule that has a partial positive end and a partial negative end because of unequal sharing of electrons.

Triple Covalent Bonds

A triple covalent bond exists when two atoms share three pairs of valence electrons. Triple bonds are stronger than double bonds.

Valence Electrons

A valence electron is an outermost electron of an atom that participates in chemical bonding. Valence electrons have the most energy of all electrons in an atom. The number of valence electrons can help determine the type and number of bonds that an element can form. Elements in certain groups have the same number of valence electrons. (group: 1, 2, 13-8)

Electron Bonding

An argon atom has 8 valence electrons, or 4 pairs of dots. There are no unpaired dots, which means that it will not easily react with other elements. Atoms with between 1 and 7 valence electrons are chemically reactive.

Ion

An ion is an atom that is no longer electrically neutral because it has either gained or lost valence electrons. Gaining electrons will make the atom negative, and losing electrons will make the atom positive. An atom with a charge ( +, -).

Electron Dot Diagrams

Are models that represent valence electrons in an atom as dots around the element's chemical symbol. The dots are placed one by one on each side of the symbol until all the dots are used. Some dots will be paired up and others will not. The number of unpaired dots is often the number of bonds an atom can form.

Ionic Compound

Are usually solid and brittle at room temperature. They have relatively high melting and boiling points. Many ionic compounds dissolve in water, making the water a good conductor of electricity.

Stable and Unstable Atoms

Atoms with unpaired dots in their electron dot diagrams are reactive, or chemically unstable. When an atom forms a bond, it gains, loses, or shares valence electrons with other atoms. Atoms with less than 8 valence electrons form bonds and become stable.

Comparing Ionic, Covalent, and Metallic Bonding

Covalent - two or more nonmetal atoms share electrons to form a molecule. Ionic - nonmetal ions bond to metal ions, and no molecules are formed. Metallic - two metals share electrons in an electron sea

Electrons and Energy

Electrons move around the nucleus at distances that relate to the amount of energy they have. The areas of space where the electrons are, are called energy levels. Electrons closest to the nucleus have the least amount of energy, and electrons farthest from the nucleus have the most amount of energy.

Nonpolar Molecule

H2 is a nonpolar molecule because the H molecules share electrons equally. A nonpolar will not dissolve easily in a polar compound. Oil is another example of a nonpolar molecule, and will not dissolve in water.

Shared Electrons

If the oxygen atom and each hydrogen atom share their unpaired valence electrons, they can form two covalent bonds and become a stable covalent compound. Each covalent bond contains two valence electrons one from hydrogen and one from oxygen. Since the electrons are shared, they count as valence electrons for both atoms in the bond. Each hydrogen atom now has 2 valence electrons. All three atoms have the electron arrangement of a noble gas, and the compound is stable.

Polar Molecule

In a covalent bond, one atom can attract the shared electrons more strongly than the other atom. In water, oxygen atoms attract the shared electrons more strongly than the hydrogen atoms do. This causes the shared electrons to be closer to the oxygen atom, making it have a slight negative charge, which causes the hydrogen atoms to have a slight positive charge.

Molecule

Is a group of atoms held together by covalent bonds that act as an independent unit. Table sugar is a covalent molecule (C12H22O11). The tiniest microscopic particle possible is a molecule of sugar.

Chemical Formula

Is a group of chemical symbols and numbers that represent the elements and number of atoms of each element that make up a compound.

Electron Transfer

Metal atoms usually lose electrons, and nonmetal atoms usually gain electrons. These ions then have opposite charges and then attract each other.

Noble Gas Electrons

Most atoms are chemically stable with 8 valence electrons, which is the same number as the noble gasses. An atom with less than 8 valence electrons becomes stable by forming chemical bonds until it has 8 valence electrons.

Covalent Bonds

Occur when two or more atoms share valence electrons. They usually have low melting points, low boiling points, are usually gases or liquids, are poor conductors of both thermal and electrical energy.

Ionic Bond

The attraction between positively and negatively charged ions in an ionic compound is an ionic bond.

Electron Arrangement

The exact position of electrons cannot be determined. This is because electrons are in constant motion around the nucleus. Each electron is usually in a certain area of space. Some are close to the nucleus and some are further away.

Gaining Valence Electrons

When an atom gains a valence electron, it becomes negative. This is because the number of electrons is now greater than the number of protons. Atoms will do this in order to become more stable in a compound.

Determining and Ion's Charge

When an atom gains or loses an electron, it becomes a charged ion. A neutral atom of nitrogen has 7 protons and 7 electrons. It usually gains 3 electrons when forming an ion. Now the ion has 10 electrons, giving it a charge of -3.

Losing Valence Electrons

When an atom loses a valence electron, it becomes positive. This is because the number of protons is now greater than the number of electrons. Atoms will do this to become more chemically stable in a chemical bond.