Chapter U2.17, Problem 4E

(a)

Interpretation Introduction

Interpretation : A partial positive or a partial negative charge is to be placed on the given pairs of atoms and the trend is to be described.

Concept Introduction :

The tendency of an atom to attract shared electrons is called electronegativity. Chemists have assigned each atom a number called electronegativity value. This number represents the tendency of the atom to attract shared electrons. The atom that has a higher electronegative value develops a partial negative charge and the atom with lower electronegative value has a partial positive charge.

Answer to Problem 4E

  ${\text{H}}^{\delta -}-{\text{B}}^{\delta +}$

Trend- Boron has a less electronegativity value than hydrogen. So here hydrogen has a partial negative charge and boron has a partial positive charge.

Explanation of Solution

The electronegativity scale is used to compare individual atoms. Atoms that are more electronegative attract bonded electrons more strongly than atoms with less electronegative value. This results in formation of a polar bond. As the difference in electronegativity increases, the bond polarity increases.

H-B- From the electronegativity scale, electronegativity value of hydrogen is 2.10 and boron is 2.04. Hence hydrogen will attract the bonded electrons more strongly than boron. So here hydrogen has a partial negative charge and boron has a partial positive charge.

  ${\text{H}}^{\delta -}-{\text{B}}^{\delta +}$

Trend- Boron is the only element amongst the given elements whose electronegativity value is less than hydrogen. So here hydrogen has a partial negative charge and boron has a partial positive charge.

(b)

Interpretation Introduction

Interpretation : The given pairs of atoms have to be arranged in order of increasing bond polarity and the trend is to be described.

Concept Introduction :

The tendency of an atom to attract shared electrons is called electronegativity. Chemists have assigned each atom a number called electronegativity value. This number represents the tendency of the atom to attract shared electrons. By comparing these numbers we can compare the polarity of bonds.The atom that has a higher electronegative value develops a partial negative charge and the atom with lower electronegative value has a partial positive charge.

Answer to Problem 4E

  ${\text{H}}^{\delta +}-{\text{C}}^{\delta -}$

Trend- Hydrogen has a less electronegativity value than carbon. So here hydrogen has a partial positive charge and carbon has a partial negative charge.

Explanation of Solution

The electronegativity scale is used to compare individual atoms. Atoms that are more electronegative attract bonded electrons more strongly than atoms with less electronegative value. This results in formation of a polar bond. As the difference in electronegativity increases, the bond polarity increases.

H-C- From the electronegativity scale, electronegativity value of hydrogen is 2.10 and carbon is 2.55. Hence, carbon will attract the bonded electrons more strongly than hydrogen. So here hydrogen has a partial positive charge and carbon has a partial negative charge.

  ${\text{H}}^{\delta +}-{\text{C}}^{\delta -}$

Trend- As we move across a period in the periodic table, the electronegativity value increases from left to right. Hydrogen has a less electronegativity value than carbon.

(c)

Interpretation Introduction

Interpretation : The given pairs of atoms have to be arranged in order of increasing bond polarity and the trend is to be described.

Concept Introduction :

The tendency of an atom to attract shared electrons is called electronegativity. Chemists have assigned each atom a number called electronegativity value. This number represents the tendency of the atom to attract shared electrons. By comparing these numbers we can compare the polarity of bonds.The atom that has a higher electronegative value develops a partial negative charge and the atom with lower electronegative value has a partial positive charge.

Answer to Problem 4E

  ${\text{H}}^{\delta +}-{\text{N}}^{\delta -}$

Trend- Hydrogen has a less electronegativity value than nitrogen. So here hydrogen has a partial positive charge and nitrogen has a partial negative charge.

Explanation of Solution

The electronegativity scale is used to compare individual atoms. Atoms that are more electronegative attract bonded electrons more strongly than atoms with less electronegative value. This results in formation of a polar bond. As the difference in electronegativity increases, the bond polarity increases.

H-N- From the electronegativity scale, electronegativity value of hydrogen is 2.10 and nitrogen is 3.04. Hence nitrogen will attract the bonded electrons more strongly than hydrogen. So here hydrogen has a partial positive charge and nitrogen has a partial negative charge.

  ${\text{H}}^{\delta +}-{\text{N}}^{\delta -}$

Trend- As we move across a period in the periodic table, the electronegativity value increases from left to right. Hydrogen has a less electronegativity value than nitrogen.

(d)

Interpretation Introduction

Interpretation : The given pairs of atoms have to be arranged in order of increasing bond polarity and the trend is to be described.

Concept Introduction :

The tendency of an atom to attract shared electrons is called electronegativity. Chemists have assigned each atom a number called electronegativity value. This number represents the tendency of the atom to attract shared electrons. By comparing these numbers we can compare the polarity of bonds.The atom that has a higher electronegative value develops a partial negative charge and the atom with lower electronegative value has a partial positive charge.

Answer to Problem 4E

  ${\text{H}}^{\delta +}-{\text{O}}^{\delta -}$

Trend- Hydrogen has a less electronegativity value than oxygen. So here hydrogen has a partial positive charge and oxygen has a partial negative charge.

Explanation of Solution

The electronegativity scale is used to compare individual atoms. Atoms that are more electronegative attract bonded electrons more strongly than atoms with less electronegative value. This results in formation of a polar bond. As the difference in electronegativity increases, the bond polarity increases.

H-O- From the electronegativity scale, electronegativity value of hydrogen is 2.10 and oxygen is 3.44. Hence oxygen will attract the bonded electrons more strongly than hydrogen. So here hydrogen has a partial positive charge and oxygen has a partial negative charge.

  ${\text{H}}^{\delta +}-{\text{O}}^{\delta -}$

Trend- As we move across a period in the periodic table, the electronegativity value increases from left to right. Hydrogen has a less electronegativity value than oxygen.

(e)

Interpretation Introduction

Interpretation : The given pairs of atoms have to be arranged in order of increasing bond polarity and the trend is to be described.

Concept Introduction :

The tendency of an atom to attract shared electrons is called electronegativity. Chemists have assigned each atom a number called electronegativity value. This number represents the tendency of the atom to attract shared electrons. By comparing these numbers we can compare the polarity of bonds.The atom that has a higher electronegative value develops a partial negative charge and the atom with lower electronegative value has a partial positive charge.

Answer to Problem 4E

  ${\text{H}}^{\delta +}-{\text{F}}^{\delta -}$

Trend- Hydrogen has a less electronegativity value than fluorine. So here hydrogen has a partial positive charge and fluorine has a partial negative charge.

Explanation of Solution

The electronegativity scale is used to compare individual atoms. Atoms that are more electronegative attract bonded electrons more strongly than atoms with less electronegative value. This results in formation of a polar bond. As the difference in electronegativity increases, the bond polarity increases.

H-F- From the electronegativity scale, electronegativity value of hydrogen is 2.10 and fluorine is 3.98. Hence fluorine will attract the bonded electrons more strongly than hydrogen. So here hydrogen has a partial positive charge and fluorine has a partial negative charge.

  ${\text{H}}^{\delta +}-{\text{F}}^{\delta -}$

Trend- As we move across a period in the periodic table, the electronegativity value increases from left to right. Hydrogen has a less electronegativity value than carbon, nitrogen oxygen and fluorine.As the difference in electronegativity values increases from carbon to fluorine, the bond polarity also increases from H-C to H-F.