Bonding and Electronegativity

Question 1

What is bonding?

Answer 1

The way atoms are bound to each other to create molecules, as great effect on physical and chemical properties of matter

Question 2

What is electronegativity?

Answer 2

The desire of one atom for the valence electron of another atom. It is also a measure of bond covalency.

Question 3

Can electronegativity be measured directly?

Answer 3

No. Instead we use the approximation I.E + E.A / 2

Question 4

What does difference in electronegativity (delta X) determine?

Answer 4

Determines how valence electrons are distributed when two atoms come together. Can be used to predict the nature of bonding.

Question 5

Discuss electronegativity and its trends in the periodic table?

Answer 5

Electronegativity increases from left to right in a period, and decreases from top to bottom in a group (same trends as I.E and E.A)

Question 6

How are ions formed?

Answer 6

When atoms with an electronegativity difference greater than 1.8 come together, valence electrons are transferred and ions are formed

Question 7

What is ionic bonding?

Answer 7

• electrostatic forces between + and - ions are closely packed into an ionic solid compound
• occurs in 3 dimensions and is delocalized (not just between 2 atoms)
• ionic crystals are repeated arrangements of cations and anions in 3D, making a lattice structure
• In ionic crystals, attractive forces (+,-) are maximized and repulsive forces (+,+) or (-,-) are minimized; holding ions together

Question 8

Describe the formation of the sodium chloride crystal.

Answer 8

1. Sodium atom transfers a valence electron to the chlorine atom, forming Na+ and Cl- ions
2. ionic bonding between those ions occur, where they are closely packed together
   - There is no NaCl molecule in solid state or aqueous solution

Question 9

Why is a lattice formed?

Answer 9

It stabilizes the ions

Question 10

What does delocalized mean?

Answer 10

Electrons are not confined to a single atom or bond, but instead are spread out over multiple atoms or bonds

Question 11

Do ionic compounds conduct electricity?

Answer 11

When dissolved in water, hydrated ions can conduct electricity

Question 12

What is covalent bonding?

Answer 12

When two atoms with similar I.E and E.A and an electronegativity difference from 0 - 1.8 come together, valence electrons are shared and a bond is formed
- covalent bonds are localized and create individual molecules

Question 13

Do ionic compounds have high melting point?

Answer 13

Yes they have a high melting point due to electrostatic attractions between ions

Question 14

What are polar covalent bonds?

Answer 14

If the electronegativity difference is between 0.4 and 1.8, it is polar covalent. This means bonding electrons are shared unequally and so bond dipoles are used to show that (only assign dipoles if the difference is 0.5 or bigger, otherwise it is not significant). The bigger the electronegativity difference, the more polar the bond

Question 15

How are larger differences in electronegativity conveyed in polar covalent bonds?

Answer 15

A larger arrow (arrow points towards the more electronegative element)