Covalent Bonding

Question 1

What is a covalent bond

Answer 1

Strong bond caused by the electrostatic attraction between the shared pair of negative electrons and the two positive nuclei. Occurs between atoms of similar and high electronegativities

Question 2

What is electronegativity and how does it change across periodic table

Answer 2

The ability of an atom to attract a shared pair of electrons in a covalent bond. Further up and right of periodic table(excluding noble gases) are more electronegative

Question 3

What would you see on an electron density map for a covalent bond

Answer 3

Continuous lines around the two nuclei due to shared electrons when atoms get closer

Question 4

Melting points of covalent compounds and why

Answer 4

Simple=relatively low due to weak IM forces between molecules
Giant covalent=high due to large number of strong covalent bonds

Question 5

Giant covalent molecules which can conduct electricity when solid

Answer 5

Graphene, graphite, nanotubes as they have delocalised electrons that can carry charge through the structure

Question 6

Solubility of covalent compounds in water and give example of exception

Answer 6

Insoluble in water unless they react to form ions eg hydrogen chloride(g) reacts to form H+ and Cl-

Question 7

Why do isotopes of the same element have similar chemical properties

Answer 7

They have the same electronic configuration and it is valence electrons that take part in reactions

Question 8

What represents a single covalent bond

Answer 8

A line between atoms

Question 9

What is a lone pair of electrons

Answer 9

A pair of electrons in the outer shell of one of the atoms in a molecule which is not involved in bonding

Question 10

What is a dative covalent bond

Answer 10

A bond in which two atoms share a pair of electrons which have both been donated by one atom

Question 11

Alternative name for a dative covalent bond

Answer 11

A co-ordinate bond

Question 12

Requirements for a dative covalent bond

Answer 12

-one atom has a lone pair of electrons
-the other atom has an empty orbital

Question 13

How is a dative bond represented in displayed formulae

Answer 13

Represented by an arrow which points from the atom donating the electron pair to the atom receiving them

Question 14

What is an orbital

Answer 14

Area surrounding nucleus where there is a high probability (95%) of finding an electron/pair of electrons with opposite spins

Question 15

What is a sigma bond and properties

Answer 15

Occurs if atomic orbitals can overlap easily and directly as it is a head-on overlap.
-bond is very strong as high level of attraction between nuclei and shared electrons due to them being close together

Question 16

What is a pi bond and properties

Answer 16

Sideways overlap of two p orbitals, electron density is above and below sigma bond(the axis)
-weaker than sigma bond as electrons are further from the nuclei meaning less attraction
-more reactive than sigma bonds, as electrons not attracted as strongly to nuclei