Chapter 5

How are metal atoms bonded in solid metal?

A metal or metal alloy consists of positively charged metal ions embedded in a "sea" of valence electrons.

Alloy

A mixture made of two or more elements that has the properties of metal.

Molecule

A neutral group of atoms joined by covalent bonds.

How do the properties of metals and alloys compare?

Alloys are generally stronger and less likely to react with air or water than are the pure metals from which they are made.

What are valence electrons?

An atom's valence electrons are those electrons that have the highest energy level and are held most loosely.

Metallic bond

An attraction between a positive metal ion and the electrons surrounding it.

What are the two basic ways in which ions form from atoms?

An ion is an atom or group of atoms that has an electric charge. When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

Molecular compound

Composed of molecules.

List three properties of ionic compounds.

In general, ionic compounds are hard, brittle crystals that have high melting points. When dissolved in water or melted, they conduct electricity.

The formula for sodium sulfide is Na2S. Explain what this formula means.

Na2S means 2 sodium (Na) atoms and 1 sulfur (S) atom per molecule.

Do oxygen atoms become more stable or less stable when oxygen forms compounds? Explain.

Oxygen atoms become more stable when oxygen forms compounds. One of two things can happen: either the number of valence electrons increases to eight, or the atom gives up loosely held valence electrons. Oxygen has six valence electrons, and that means it needs to gain two to become stable, but it takes much more energy for oxygen to lose its 6 valence electrons than it would be to gain 2. When atoms form compounds, they become stable.

Summarize how the periodic table is organized, and tell why this organization is useful.

Recall that the periodic table is organized by atomic number - the number of protons in the nucleus of an atom. The periodic table gives you information about the arrangement of electrons in atoms.

Contrast sodium and chloride ions, including how they form. Write the symbol for each ion.

Sodium ions are positive as the Na atom loses an electron to become Na+ Chloride ions are negative as the Cl atom gains an electron to become Cl-

How does metallic bonding result in useful properties of metals?

The "sea of electrons" mode of solid metals explain the ease with which they can change shape, their ability to conduct electric current, their luster, and their ability to conduct heat.

What information can the periodic table gives you?

The arrangement of electrons in atoms.

What is the force that holds atoms together in a covalent bond??

The attraction of each atom's nucleus for the shared pair of electrons.

Covalent bond

The chemical bond formed when two atoms share electrons.

How reactive are the elements in Group 18? Explain this reactivity in terms of the number of valence electrons.

The elements in Group 18 are not reactive because of the octet rule. They already have 8 valence electrons which is a full energy level so they don't react with anything.

Why do the properties of elements change in a regular way across a period?

The elements within a group have similar properties because they all have the same number of valence electrons in their atoms.

How is the reactivity of elements related to valence electrons in atoms?

The number of valence electrons an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.

What role do valence electrons play in the formation of compounds from elements?

The number of valence electrons in an atom of an element determines many properties of that element, including the ways in which the atom can bond with other atoms.

Double bond

Two atoms share two pairs of electrons.

How do ions bond?

When an atom loses an electron, it loses a negative charge and becomes a positive ion. When an atom gains an electron, it gains a negative charge and becomes a negative ion.

What holds the ions together in sodium chloride? Indicate the specific charges that are involved.

When an electron of sodium atom is transferred to chlorine atom it forms sodium chloride. This chemical bonding gives Na+ and Cl-. The electrons are of opposite charges so they are attracted to each other and the end result is the formation of NaCl.

What information is given by the formula of an ionic compound?

When ionic compounds form, the ions come together in a way that balances out the charges on the ions. The chemical formula for the compound reflects this balance.