Bonding and Structure

Question 1

Ionic bonding

Answer 1

The electrostatic attraction between oppositely-charged ions

Question 2

Formula for nitrate ion, carbonate ion, sulfate ion and ammonium ion

Answer 2

NO(3)^2- , CO(3)^2- , SO(4)^2- , NH(4)^+

Question 3

Covalent bond

Answer 3

A shared pair of electron

Question 4

What is the shape of a molecule determined by?

Answer 4

The repulsion between electron pairs surrounding the central atom

Question 5

What type of electron pairs repel most?

Answer 5

Lone pairs repel more than bonded pairs

Question 6

Trigonal planar molecules

Answer 6

3 bonded pairs, no lone pairs; bond angle of 120; e.g. BF(3)

Question 7

Tetrahedral molecules

Answer 7

4 bonded pairs, no lone pairs; bond angle of 109.5; e.g. CH(4) or NH(4)^+

Question 8

Octahedral molecules

Answer 8

6 bonded pairs, no lone pairs; bond angle of 90; e.g. SF(6)

Question 9

Pyramidal molecules

Answer 9

3 bonded pairs, 1 lone pair; bond angle of 107; e.g. ammonia, NH(3)

Question 10

Non-linear (V or bent shaped) molecules

Answer 10

2 bonded pairs, 2 lone pairs; bond angle of 104.5; e.g. water, H(2)O

Question 11

Linear molecules

Answer 11

2 bonded pairs/bonding regions; bond angle of 180; e.g. CO(2)

Question 12

Electronegativity

Answer 12

The ability of an atom to attract the bonding electrons towards itself in a covalent bond

Question 13

When may a permanent dipole arise?

Answer 13

When covalently bonded atoms have different electronegativities, resulting in a polar bond

Question 14

Permanent dipole-dipole interactions

Answer 14

The permanent dipole of one molecule attracts the permanent dipole in a different polar molecule towards itself, forming a weak permanent dipole-dipole force. delta + attracts delta -

Question 15

Van der Waals’ forces

Answer 15

Exist between all molecules. Intermolecular attractions between small, temporary dipoles in neighbouring molecules. An instantaneous dipole may form due uneven distribution of electrons, inducing a dipole in the molecule next to it, creating weak intermolecular forces due to the attraction. The more electrons, the stronger the forces. The more points of contact, the stronger the forces

Question 16

Hydrogen bonding

Answer 16

Strong dipole-dipole interaction between an electron-deficient hydrogen atom (delta +) on one molecule and a lone pair of electrons on a highly electronegative atom on a different molecule. In molecules with O-H and N-H groups. When drawing, draw Hd+, dashed line, lone pair on O/Nd- in line with another H.

Question 17

Anomalous properties of water

Answer 17

• ice is less dense than water: open lattice of hydrogen bonds hold water molecules apart. These collapse when ice melts, allowing water molecules to move closer together
• water has relatively high freezing and boiling point: hydrogen bonds are an extra intermolecular force to be overcome when melting/boiling water.
• high surface tension and viscosity

Question 18

Metallic bonding

Answer 18

The electrostatic attraction of positive ions to delocalised electrons

Question 19

Giant metallic structures

Answer 19

Strong metallic bonds between positive metal ions and delocalised electrons results in high melting point and a good conductor of electricity and heat

Question 20

Giant covalent structures

Answer 20

Strong covalent bonds between atoms results in a very high melting point. Don’t conduct as no mobile charges EXCEPT graphite, which has delocalised electrons between layers

Question 21

Giant ionic structures

Answer 21

Strong ionic bonds between oppositely charged ions results in high melting point. Ions fixed in solid lattice, but conduct electricity when molten/in solution as ions can then move

Question 22

Dative covalent bond

Answer 22

A shared pair of electrons (covalent bond) where both electrons are donated by one atom