1.3 Bonding Definitions

Question 1

Define Co-ordinate bond (dative covalent bond)

Answer 1

A co-ordinate (dative covalent) bond contains a shared pair of electrons supplied by one atom

Question 2

Define Covalent bond

Answer 2

A shared pair of electrons between two non-metals

Question 3

Define Dipole

Answer 3

Difference in charge between the two atoms of a covalent bond caused by a shift in electron density in the bond due to the electronegativity difference between elements participating in bonding

Question 4

Define Electron pair repulsion

Answer 4

Repulsion that exists between electron pairs due to the negatively charge electrons. This repulsion means electron pairs position themselves as far apart from each other as possible around the central metal atom

Question 5

Define Electronegativity

Answer 5

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

Question 6

Define Electrostatic forces

Answer 6

The strong forces of attraction between oppositely charged ions

Question 7

Define Hydrogen bonding

Answer 7

An interaction between a hydrogen atom and an electronegative atom, commonly nitrogen, fluorine or oxygen. The slightly positive hydrogen is attracted to the lone pair on the electronegative atom. Hydrogen bonds are stronger than Van der Waals and dipole-dipole forces but are weaker than ionic and covalent bonds

Question 8

Define Intermolecular forces

Answer 8

The forces that exist between molecules. The strength of the intermolecular forces impact physical properties like boiling/melting point.

Question 9

Define Ion

Answer 9

An atom or molecule with an electric charge due to the loss or gain of electrons

Question 10

Define Ionic bond

Answer 10

A metal atom loses electron(s) to form a positively charged ion and a non-metal atom gains these electron(s) to form a negatively charged ion. An ionic bond is formed between the oppositely charged ions.

Question 11

Define Ionic compound

Answer 11

Chemical compound formed of ions, held together by strong electrostatic forces.

Question 12

Define Lattice

Answer 12

A repeating regular arrangement of atoms/ions/molecules. This arrangement occurs in crystal structures

Question 13

Define Macromolecular crystal structure

Answer 13

Giant covalent structures. Macromolecules have very high melting points because many strong covalent bonds have to be broken. Examples include diamond and graphite

Question 14

Define Metallic bond

Answer 14

The bonds present in metals between positive metal ions and negatively charged electrons

Question 15

Define Permanent dipole-dipole forces

Answer 15

When molecules with polar covalent bonds interact with dipoles in other molecules dipole-dipole intermolecular forces are produced between the molecules. These intermolecular forces are generally stronger that van der Waals’ forces but weaker than hydrogen bonding

Question 16

Define Polar bond

Answer 16

A covalent bond between two atoms in which the electrons in the bond are unevenly distributed. This causes a slight charge difference, including a dipole in the molecule.

Question 17

Define Simple molecular crystal structure

Answer 17

Structures in which the atoms are joined by strong covalent bonds. Weak intermolecular forces mean simple molecules have a low melting and boiling points

Question 18

Define Van der Waals’

Answer 18

Also known a induced dipole-dipole, dispersion and London forces, van der Waals’ forces exists between all molecules. These arise due to fluctuations of electron density within a non-polar molecules. These fluctuations may temporarily cause an uneven electron distribution, producing an instantaneous dipole. This dipole can induce a dipole in a neighbouring molecule, and so on.

Question 19

Define VSEPR theory

Answer 19

Valence shell electron pair repulsion theory is used to deduce the geometry of molecules. Pairs of electrons in the outer shell of atoms arrange themselves as far apart as possible to minimise repulsion. Lone pair-lone pair repulsion is greater then lone pair-bond pair repulsion, which is greater than bond pair-bond pair repulsion.