2.2.6 Covalent bonding

Question 1

what does covalent bonding occur between?

Answer 1

between two non-metals

Question 2

how is a covalent bond formed?

Answer 2

the negatively charged pair of e- is attracted to the positive charges of BOTH nuclei, this attraction overcomes the repulsion between the two positively charged nuclei (attraction is the bond)

Question 3

in covalent bonding, are electrons transferred or shared?

Answer 3

covalent bonding is sharing electrons

Question 4

what does the number of electrons needed to obtain a noble gas configuration correspond with exactly?

Answer 4

the number of covalent bonds an element forms

Question 5

how many electrons are shared in a single bond? C-C

Answer 5

2

Question 6

how many electrons are shared in a double bond?

Answer 6

4

Question 7

how many electrons are shared in a triple bond?

Answer 7

6

Question 8

what is bond energy?

Answer 8

the energy required to break one mole of a particular covalent bond in the gaseous states

Question 9

what is the unit for bond energy?

Answer 9

kJ mol-1

Question 10

what effect does bond energy have, on the strength of covalent bonds?

Answer 10

the larger the bond energy, the stronger the covalent bonds

Question 11

apart from bond energy, what else can measure the strength of a covalent bond?

Answer 11

average bond enthalpy

Question 12

what is average bond enthalpy?

Answer 12

the average amount of energy needed to break a specific type of bond, measured over a wide variety of different molecules

Question 13

what is bond length?

Answer 13

internuclear distance of two covalently bonded atoms (it is the distance from the nucleus of one atom to another atom which forms the covalent bond)

Question 14

the greater the forces of attraction between electrons and nuclei…

Answer 14

…the more the atoms are pulled closer to each other

Question 15

what is the effect of greater forces of attraction between electrons and nuclei?

Answer 15

this decreases the bond length of a molecule and increases the strength of the covalent bond

Question 16

the shorter the bond length…

Answer 16

the stronger the covalent bond

Question 17

which bond is the shortest and the strongest? single, double or triple

Answer 17

triple

Question 18

why are triple bonds the shortest and tf the strongest?

Answer 18

due to the large electron density between the nuclei of the two atoms

Question 19

explain how electron density between the nuclei of the two atoms causes the covalent bond to be stronger

Answer 19

if there is a large electron density between the nuclei of the two atoms, this increases the forces of attraction between the electrons and nuclei of the atoms
as a result of this, the atoms are pulled closer together causing a shorter bond length, the increased forces of attraction also means that the covalent bond is stronger

Question 20

what is a lone pair?

Answer 20

when an atom in a molecule has a pair of non-bonding electrons

Question 21

what is expanding the octet rule?

Answer 21

being able to accommodate more than 8 electrons in the outer shell

Question 22

what does it mean if the central atom is ‘electron deficient’?

Answer 22

it accommodates less than 8 electrons in the outer shell means than the central atom

Question 23

what is a dative covalent bond also known as?

Answer 23

a coordinate covalent bond

Question 24

what is an electron deficient atom?

Answer 24

an atom that has an unfilled outer orbital

Question 25

what is dative covalent bonding?

Answer 25

a lone pair of electrons can be donated to form a bond with an electron-deficient atom

Question 26

what does dative covalent bonding mean, in terms of electron origin?

Answer 26

both electrons are from one atom, in the covalent bond

Question 27

how is a dative bond represented?

Answer 27

using an arrow from the donated pair of electrons to the electron-deficient atom.