Bond Polarity

Question 1

Why do electrons shared between atoms, tend to not be evenly spread?

Answer 1

Electrons shared may not be evenly spread if one atom is better at attracting electrons than the other

Question 2

The uneven spread of electrons shared between atoms is known as electronegativity. What is electronegativity?

Answer 2

The power of an atom to attract the electron density of a pair of electrons in a covalent bond towards itself

Question 3

What does the term electron density refer to?

Answer 3

The term “electron density” is often used to describe the way the negative charge is distributed in a molecule

Question 4

What is a scale used to measure electronegativity?

Answer 4

The Pauling scale

Question 5

Why do the noble gases have no number on the pauling scale?

Answer 5

The noble gases have no number on the pauling scale because they generally do not form covalent bonds

Question 6

What three things does electronegativity depend on?

Answer 6

1. The nuclear charge
2. The distance between the nucleus and the outer shell electrons
3. The shielding of the nuclear charge created by electrons in inner shells

Question 7

When an atom is smaller, what this result in?

Answer 7

The smaller an atom, the closer the nucleus is to the shared outer main level electrons and the greater electronegativity is

The nucleus is closer to the edge of the atom so it can reach for the elcetrons it is bonding with easier than a nucleus that is hidden behind may shells

Question 8

When an atom has a large nuclear charge, what does this result in?

Answer 8

When an atom has a larger nuclear charge, it can attract electrons more (greater positive attract weak negative) making a greater electronegativity

Question 9

As you go up a group on the periodic table, what happens to electronegativity?

Answer 9

As you go up the periodic table, electronegativity increases, because the atoms get smaller and there is less shielding from the electrons in inner shells

Question 10

As you go across a period in the periodic table, what happens to electronegativity?

Answer 10

Going across a periodic table, electronegativity increases. This is because the nuclear charge increases so the number of inner main levels remains the same but atoms become smaller

Question 11

What are the most electronegative atoms?

Answer 11

Fluorine, Oxygen, Nitrogen and Chlorine

Question 12

What is polarity?

Answer 12

Polarity is the unequal sharing of the electrons between atoms that are bonded together covalently. This is a property of the bonding

Question 13

If two of the same atoms become covalently bonded, what does this make their bond?

Answer 13

Two of the same atoms covalently bonded, makes the bond becomes equally shared, making the bond non - polar

Question 14

Using hydrogen and fluorine, explain what their covalent bond would result in?

Answer 14

Hydrogen has an electronegativity of 2.1 and fluorine has an electronegativity of 4.0

This means electrons in the covalent bond will be attracted to fluorine more than hydrogen

The fluorine end of the molecule is therefore relatively negative; the hydrogen molecule is therefore relatively positive

Question 14

If two different atoms of different electronegativity become covalently bonded, what does this make their bond?

Answer 14

If two different atoms of different electronegativity form a covalent bond, it results in an unequally shared bond between the atoms.

Question 15

How is the relative positivity of an atom shown? How is the relative negativity of an atom shown?

Answer 15

To show relative positivity a delta plus sign is shown, to show relative negativity a delta minus sign is shown