Science Chapter 5

Write the formula for calcium chloride. Explain how you determined this formula.

Ca2+ - I need to give away 2 electrons Cl- - I need to get 1 electron. ×2 CaCl2

A carbon atom can form four covalent bonds. How many valence electrons does it have?

Four; the number of valence electrons is the same as the number of bonds.

List three properties of ionic compounds.

Ionic compounds are hard, brittle crystals that have high melting points and conduct electricity when dissolved in water or melted.

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

It means that Na has 2 sodium ions, and S has 1 sulfide ion. The sodium ions each gave up 1 electron for a total of 2. These 2 electrons were accepted by the sulfide ion.

How are the properties of molecular compounds different from those of ionic compounds?

Molecular compounds generally have lower melting points and boiling points and they do not conduct electricity when dissolved in water. Ionic compounds give and receive electrons, and makes charged particles.

Why are most molecular compounds poor conductors of electricity?

No charged particles are available to move, so there is no electric current.

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

Sodium (Na) Na+/becomes ion when it lost an electron Chloride (Cl) Cl-/becomes ion when it gained an electron

What is the attraction that holds two covalently bonded atoms together?

The attraction of the nucleus to the valence electrons.

What are valence electron?

The electrons that are in the highest energy level of an atom and are held the most loosely.

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

The name of the ions and the ratio of ions.

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

The periodic table is organized by increasing atomic number, the rows are called periods and the columns are called groups, and you read across and then down like a calendar. Elements in the same group have the same properties.

Relate each property that you listed to the characteristics of ionic bonds.

They also are hard, brittle crystals, have high melting points, and conduct electricity when dissolved in water or melted.

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

They are held together by the attraction between the oppositely charged ions. Ex. K+ Cl- ✔ Na+ Li+ ✖

How do some atoms in covalent bonds become slightly negative or slightly positive? What type of covalent bonds do these atoms form?

They don't share equally so some atoms pull more on electrons. These atoms form polar bonds.

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

Valence electrons are involved in bonding and they are either transferred between atoms or shared by atoms.

Predict whether carbon dioxide or water would have a higher boiling point.

Water, because it takes more energy to break a polar bond.

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

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

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

When oxygen forms compounds, it gains or shares electrons giving each oxygen atom eight valence electrons making it stable.

What is a double bond? Use figure 16 to explain how a carbon dioxide molecule has a stable set of eight valence electrons for each atom.

A double bond is a chemical bond formed when atoms share two pairs of electrons. The carbon dioxide molecule has 2 double bonds, so when atoms share, carbon has 8 valence electrons and both oxygens have 8 valence electrons.