What is true about all What is true about all substances?substances?

Every substance is either an element or a Every substance is either an element or a compound.compound.

All substances are “pure”, by definition.All substances are “pure”, by definition.

A compound consists of more than one A compound consists of more than one kind of atom.kind of atom.

The elements in a compound exist in a The elements in a compound exist in a definite proportion by mass.definite proportion by mass.

What is true about What is true about compounds?compounds?

Where would the elements Where would the elements in a molecular compound be in a molecular compound be found on the periodic table?found on the periodic table?

Molecular compounds consist of elements Molecular compounds consist of elements from the nonmetal portion of the periodic from the nonmetal portion of the periodic

table.table.

Where would the elements Where would the elements in an ionic compound be in an ionic compound be

found on the periodic table?found on the periodic table?Ionic compounds consist of elements from Ionic compounds consist of elements from both the metal and nonmetal portions of the both the metal and nonmetal portions of the

periodic table.periodic table.

What are the two types of What are the two types of compounds?compounds?

A compound is either molecular or ionic A compound is either molecular or ionic in nature.in nature.

What information is given by What information is given by a molecular formula?a molecular formula?

A molecular formula shows the number A molecular formula shows the number and kinds of atoms present in a molecule and kinds of atoms present in a molecule

of a compound.of a compound.

What information is given by What information is given by the molecular formulas listed the molecular formulas listed

below:below:CO and COCO and CO22??

CO means one carbon and one oxygen;CO means one carbon and one oxygen;

COCO22 means one carbon and two oxygen. means one carbon and two oxygen.

Why do ionic compounds Why do ionic compounds conduct current when part of conduct current when part of

an aqueous solution?an aqueous solution?

Ionic compounds are composed of Ionic compounds are composed of oppositely charged ions combined in oppositely charged ions combined in

electrically neutral groupings. Because electrically neutral groupings. Because they are composed of ions, they easily they are composed of ions, they easily

dissolve in water and conduct electricity.dissolve in water and conduct electricity.

NaCl crystals are composed NaCl crystals are composed of alternating units of Na of alternating units of Na

and Cl. Why isn’t the and Cl. Why isn’t the formula something like formula something like

NaNa124124ClCl124124??A formula unit gives the lowest whole-A formula unit gives the lowest whole-number ratio of ions in the compound. number ratio of ions in the compound.

Since we don’t know how many units of Since we don’t know how many units of each atom, it makes sense to use the each atom, it makes sense to use the

least common multiple.least common multiple.

The charges of the ions of the The charges of the ions of the representative elements can be representative elements can be

determined by the position of these determined by the position of these elements in the periodic table.elements in the periodic table.

?

Most Most transition metals have transition metals have more than one common more than one common

ionic charge.ionic charge.

Why do we not predict the charges of transition metals

from their positions in the periodic table?

What is an ion such asWhat is an ion such asOHOH1-1- or SO or SO44

2-2-??

A A polyatomic ionpolyatomic ion is a group of atoms that is a group of atoms that behaves as a unit and has a charge.behaves as a unit and has a charge.

Why do both iron(II) and iron Why do both iron(II) and iron (III) appear on our list of (III) appear on our list of

cations?cations?

When a cation can have more than one When a cation can have more than one ionic charge, a Roman numeral is used in ionic charge, a Roman numeral is used in

the name.the name.

For both, we write the least electronegative (most positive) first, For both, we write the least electronegative (most positive) first, followed the less electronegative atom.followed the less electronegative atom.

There are simple rules for naming ionic and There are simple rules for naming ionic and molecular compounds. The first rule is listed molecular compounds. The first rule is listed

below. What is different about naming an ionic below. What is different about naming an ionic compound than a molecular compound?compound than a molecular compound?

1.1. For ionic compounds, we just list the cation, then the For ionic compounds, we just list the cation, then the anion.anion.For molecular compounds, you use prefixes. For molecular compounds, you use prefixes. The less electronegative atom only gets a prefix if there The less electronegative atom only gets a prefix if there is more than one.is more than one.For the more electronegative ion, you always use a For the more electronegative ion, you always use a prefix, then you use the – ide ending.prefix, then you use the – ide ending.Ex: Carbon monoxide, carbon dioxide, dinitrogen Ex: Carbon monoxide, carbon dioxide, dinitrogen pentoxide.pentoxide.

Elements that have similar properties Elements that have similar properties also have similar electron configurations also have similar electron configurations

and are members of the same group.and are members of the same group.

What do you know about theelectron configuration and chemical reactivity of an atombased on this picture?

Sodium would lose electrons more easily Sodium would lose electrons more easily because there is more shielding.because there is more shielding.

Since Li has the electron configuration 1s22s1

and sodium has the electronconfiguration 1s22s22p63s1

Which would lose electrons moreeasily?

Lithium would lose electrons more easily than Lithium would lose electrons more easily than beryllium because there is less shielding.beryllium because there is less shielding.

Since Li has the electron configuration 1s22s1

and beryllium has the electronconfiguration 1s22s2

Which would lose electrons moreeasily?

As we go down a group, the density As we go down a group, the density increases.increases.

We found the densityof silicon, tin, and lead.As we went down a groupwe noticed a periodic trend.What trend did we notice?

As we go down a group, the chemical As we go down a group, the chemical reactivity increases.reactivity increases.

Magnesium metal canbe purchased in pure form.Calcium metal can be purchased, but usually oxidizes soon after.Strontium can only be purchased (by a high school teacher) in the oxidizedform. What periodic trend does thisillustrate?

Regular changes in the electron configuration of the elements cause gradual changes Regular changes in the electron configuration of the elements cause gradual changes in both the physical and chemical properties within a group and within a period. And, in both the physical and chemical properties within a group and within a period. And,

as a result, theas a result, the

atomic radii decrease as you move from left to right in a given atomic radii decrease as you move from left to right in a given period.period.

What does this graph show?

Regular changes in the electron configuration of the elements cause gradual changes Regular changes in the electron configuration of the elements cause gradual changes in both the physical and chemical properties within a group and within a period. And, in both the physical and chemical properties within a group and within a period. And,

as a result, theas a result, theatomic radii generally increase as you go down a group, and decrease as atomic radii generally increase as you go down a group, and decrease as

you go across a period.you go across a period.

What does this picture show?

The graph shows that electronegativity The graph shows that electronegativity increases across a period and decreases increases across a period and decreases

down a group.down a group.

What does this graphshow?

What do the red dots What do the red dots represent?represent?

The red dots represent valence The red dots represent valence electronselectrons

What do the red dots represent? What do the red dots represent? How do they vary with position on How do they vary with position on the periodic table?the periodic table?

The red dots represent valence The red dots represent valence electronselectrons

The number of dots is the same as The number of dots is the same as the group number (except for helium)the group number (except for helium)

Summary of goals for Summary of goals for Unit 5Unit 5

Every substance is either an element or a compound.Every substance is either an element or a compound.A compound consists of more than one kind of atom.A compound consists of more than one kind of atom.

A compound is either molecular or ionic in nature.A compound is either molecular or ionic in nature.Molecular compounds are composed of two or more nonmetals.Molecular compounds are composed of two or more nonmetals.

A molecular formula shows the number and kinds of atoms present in a molecule of a A molecular formula shows the number and kinds of atoms present in a molecule of a compound.compound.

Ionic compounds are composed of oppositely charged ions combined in electrically neutral Ionic compounds are composed of oppositely charged ions combined in electrically neutral groupings.groupings.

A formula unit gives the lowest whole-number ratio of ions in the compound.A formula unit gives the lowest whole-number ratio of ions in the compound.The charges of the ions of the representative elements can be determined by the position of The charges of the ions of the representative elements can be determined by the position of

these elements in the periodic table.these elements in the periodic table.Most transition metals have more than one common ionic charge.Most transition metals have more than one common ionic charge.

A polyatomic ion is a group of atoms that behaves as a unit and has a charge.A polyatomic ion is a group of atoms that behaves as a unit and has a charge.When a cation can have more than one ionic charge, a Roman numeral is used in the name.When a cation can have more than one ionic charge, a Roman numeral is used in the name.

There are simple rules for naming ionic and molecular compounds.There are simple rules for naming ionic and molecular compounds.Elements that have similar properties also have similar electron configurations and are Elements that have similar properties also have similar electron configurations and are

members of the same group.members of the same group.Regular changes in the electron configuration of the elements cause gradual changes in both Regular changes in the electron configuration of the elements cause gradual changes in both

the physical and chemical properties within a group and within a period.the physical and chemical properties within a group and within a period.Atomic radii decrease as you move from left to right in a given period.Atomic radii decrease as you move from left to right in a given period.

Ionization energy increases as you move from left to right in a given period.Ionization energy increases as you move from left to right in a given period.Atomic radii increase within a given group because the outer electrons are farther from the Atomic radii increase within a given group because the outer electrons are farther from the

nucleus as you go down the group.nucleus as you go down the group.Ionization energy decreases as you move down through a group.Ionization energy decreases as you move down through a group.