Bonding

Question 1

Co-ordinate bond

Answer 1

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

Question 2

Covalent bond

Answer 2

A shared pair of electrons between two non-metals

Question 3

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

Electron pair repulsion

Answer 4

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

Question 5

Electronegativity

Answer 5

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

Question 6

Electrostatic forces

Answer 6

The strong forces of attraction between oppositely charged ions

Question 7

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 weaker than ionic and covalent bonds

Question 8

Intermolecular forces

Answer 8

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

Question 9

Ion

Answer 9

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

Question 10

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

Ionic compound

Answer 11

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

Question 12

Lattice

Answer 12

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

Question 13

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

Metallic bonding

Answer 14

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

Question 15

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 than van der Waals forces but weaker than hydrogen bonding

Question 16

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, inducing a dipole in the molecule

Question 17

Simple molecular crystal structure

Answer 17

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

Question 18

Van der Waals

Answer 18

Also known as induced dipole-dipole, dispersion and London forces, van der Waals forces exist between all molecules. They arise due to fluctuations of electron density with a nonpolar molecule. These fluctuations may temporarily cause an uneven electron distribution, producing an instantaneous dipole. This dipole can induce a dipole in another molecule, and so on

Question 19

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 than lone pair-bond pair repulsion, which is greater than bond pair-bond pair repulsion