Valence Electrons
Ionic Bonds
Covalent Bonds
Polarity
Metals and More
100
How many valence electrons does Sulfur have? What ion does sulfur form?
Sulfur has 6 valence electrons. Sulfur forms an anion with a 2- charge.
100
When an ionic bond forms, the metal atoms ________ electrons, while the nonmetal atoms __________ electrons.
The metal atoms lose electrons, while the nonmetals gain electrons.
100
Valence electrons in a covalent bond are ____________ between two atoms.
shared
100
What property or force determines whether a chemical bond is ionic, polar covalent, or nonpolar covalent?
Electronegativity (an atom's ability to pull electrons towards itself in a bond) determines whether the bond will be ionic, polar covalent, or nonpolar covalent.
100
What are three properties of metals?
Properties: high melting point, malleable, ductile, lustrous, does not dissolve in water, conducts electricity and heat in the solid state, solid at room temperature.
200
How many valence electrons does Francium have? What ion does Francium form?
Francium has 1 valence electron. Francium forms a cation with a 1+ charge.
200
How many fluorine atoms are in the compound calcium fluoride?
2 fluorine atoms for every 1 calcium atom.
200
How many valence electrons are in a single covalent bond? How many valence electrons are in a double covalent bond? How many valence electrons are in a triple covalent bond?
2, 4, 6
200
What is the trend (pattern) for electronegativity on the periodic table?
Electronegativity increases from left to right across a period and increases from the bottom to the top of the table. But, the noble gases (group 18) have no electronegativity.
200
Describe a metallic bond.
In a piece of metal the metal atoms form a crystal structure and they all give up their valence electrons to form a sea of free flowing (delocalized) electrons. The electrostatic attraction between the delocalized electrons and the metal cations are responsible for many of metals' unique properties.
300
How many valence electrons do atoms in group 15 have? When forming covalent bonds, how many bonds do these elements want to make? Why?
Group 15 elements have 5 valence electrons. When covalent bonding, they make 3 bonds. This is due to the fact that they want to fill their outer energy level with a total of 8 valence electrons. (That is known as the octet rule.)
300
Describe the structure of ionic compounds and give three properties of ionic compounds that result from this structure.
Ionic compounds form a crystal lattice structure with anions surrounded by cations in the proportion (ratio) shown in the compound formula. Properties: high melting point, hard, brittle, solid at room temperature.
300
Why do nonmetals form covalent bonds?
Nonmetal atoms have similar electronegativity values. This means that both atoms pull electrons towards themselves with similar strength. All nonmetals are close to meeting the octet rule. Therefore, they "share" the electrons so that both atoms can be more stable and have a full outer shell of valence electrons.
300
Based on differences in electronegativity, do you expect HF (Hydrogen Fluoride) to be ionic, polar covalent, or nonpolar covalent? Why?
HF is a polar covalent compound because F is significantly more electronegative than H. However, they are both non-metals and both want to gain electrons. Therefore, their electronegativity values are not as different as in an ionic compound.
300
What is the difference between copper metal (Cu) and copper (II) oxide (CuO)?
Copper metal is a metallic compound with copper cations held together through metallic bonding. This involves delocalized electrons. Copper oxide is an ionic compound. Copper transfers electrons to oxygen and a crystal lattice structure is formed. The crystal lattice contains cations and anions.
400
What type of ions do metals always form? Why?
Metals always form cations (positive ions). They do this because their outer shell (energy level) is close to empty. In other words, metals have small amounts of valence electrons. It takes less energy to lose 1, 2, or 3 valence electrons than to gain 5 or more. Therefore, metals lose electrons to have their next inner energy shell full and stable.
400
Small ionic compounds like sodium chloride (NaCl) dissolve in water. Describe what happens at the molecular level when sodium chloride dissolves in water.
The water surrounds the ions with the positive hydrogen side of water attracted to the negative anions (chlorine) and the negative oxygen side of water attracted to the positive cations (sodium). These attractions break the crystal lattice structure. The anions and cations separate and are surrounded fully by water in solution.
400
List three properties of nonpolar covalent compounds and three properties of polar covalent compounds.
Nonpolar covalent compounds have low melting points, are soft and flexible, do not conduct electricity, and do not dissolve in water. Polar covalent compounds also have low melting points, are soft and flexible, do not conduct electricity, but they do dissolve in water.
400
Why don't oil and water mix?
Oil is a nonpolar covalent compound and water is a polar covalent compound. Water molecules are attracted to each other through hydrogen bonding. Oil molecules are not attracted to water. This is an example of the "like dissolves like" rule.
400
Are most of the elements metals, semimetals, or nonmetals? What are the names of the groups (or families) of metals on the periodic table?
Metals. The alkali metals, alkaline earth metals, transition metals, lanthanides, and actinides make up most of the elements.
500
Magnesium has 12 electrons and Calcium has 20. But, they have the same number of valence electrons. How many valence electrons do they have and why?
Mg and Ca have 2 valence electrons each. This is possible because Ca has one more energy level than Mg. Mg has 10 electrons in energy levels 1 and 2. Ca has 18 electrons in energy levels 1, 2, and 3. They each have the last 2 electrons in their "valence" or outer energy level.
500
In the ionic and covalent bonding labs, students observed that ionic compounds conduct electricity when dissolved in water. But, covalent compounds do not conduct electricity when dissolved. Why?
Ionic compounds conduct electricity when dissolved in water because the ions have an electrical charge. Cations are positive and anions are negative. This allows for electricity (a current of electrons) to flow through the solution. Covalent compounds (even polar ones) do not contain charged particles.
500
Why does the molecule structure for carbon dioxide (CO2) contain double bonds linking each oxygen to carbon?
Carbon has 4 valence electrons and wants to make 4 bonds to meet the octet rule and have a full valence shell. Each oxygen has 6 valence electrons and wants to make two bonds the meet the octet rule and have a full valence shell. Therefore, each oxygen shares two electrons with carbon and carbon shares two electrons with oxygen to make 2 double bonds.
500
In the penny challenge lab students observed that the number of drops of water that fit on the penny decreased when the penny was dipped in soap. Why?
Water is a polar molecule. It sticks to itself (cohesion) because of hydrogen bonding. It sticks to metals (adhesion) because metals contain charged particles (positive cations and a sea of electrons). The polar (partially charged) water molecule is attracted to the charged particles in metal. But, soap breaks up the hydrogen bonds because it contains large molecules that are partly nonpolar. These nonpolar sections repel the water.
500
What day is the unit exam and what do you need to turn in on the day of the unit exam?
The unit exam is Tuesday Feb. 02. Turn in your notes packet and your study guide.
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