5) Electrons and bonding

Question 1

Energy increases as shell number _?

Answer 1

increases

Question 2

Define principal quantum number n

Answer 2

a number representing the relative overall energy of each orbital, which increases with distance from the nucleus

Question 3

What are the sets of orbitals with the same n-value referred to as?

Answer 3

electron shells or energy levels

Question 4

Define atomic orbital

Answer 4

a region around the nucleus that can hold up to 2 e-, with opposite spins

Question 5

Describe a s-orbital

Answer 5

spherical shape

as n increases, radius increases

Question 6

Describe a p-orbital

Answer 6

dumb-bell shape

as n increases, reaches further away from the nucleus

Question 7

Define sub-shell

Answer 7

a group of orbitals of the same type within a shell

Question 8

Describe the filling of orbitals

Answer 8

orbitals fill in order of increasing energy
electrons pair with opposite spins
orbitals with the same energy are occupied singly first (bus-seating rule)

Question 9

What is special about the 3d sub-shell?

Answer 9

it is at a higher energy level than the 4s sub-shell so it is filled after and emptied after the 4s sub-shell

Question 10

What does electron pairing with opposite spins help to do?

Answer 10

counteract the repulsion between the negative charges of the 2 electrons

Question 11

When orbitals with the same energy are occupied singly first (bus-seating rule), what does it prevent?

Answer 11

any repulsion between paired electrons until there is no further orbital available at the same energy level

Question 12

Define electron configuration

Answer 12

a shorthand representation that shows how electrons occupy sub-shells in an atom

Question 13

In an electron configuration, how are shells listed?

Answer 13

in shell order rather than in order of filing

Question 14

How can electron configurations be expressed more simply?

Answer 14

in terms of previous noble gas plus outer electron sub shells

Question 15

When are positive ions / cations formed?

Answer 15

when atoms lose electrons

Question 16

When are negative ions / anions formed?

Answer 16

when atoms gain electrons

Question 17

Define ionic bonding

Answer 17

the electrostatic attraction between positive and negative ions

Question 18

In ionic bonding electrons are _ whereas, in covalent bonding electrons are _?

Answer 18

transferred

shared

Question 19

Define giant ionic lattice

Answer 19

3D structure of oppositely charged ions, bonded together by strong ionic bonds

Question 20

Give 3 features of giant ionic lattices

Answer 20

high melting and boiling points
many dissolve in polar solvents e.g. water
conducts electricity as a liquid or aqueous solution

Question 21

Why do ionic lattices containing ions with greater ionic charges have higher melting points?

Answer 21

there is stronger attraction between ions

Question 22

What two conditions must be met for a giant ionic lattice to dissolve in a polar solvent?

Answer 22

the ionic lattice is broken down

solvent molecules e.g. water attract and surround the ions in solution

Question 23

How are giant ionic lattices able to conduct electricity as a liquid or aqueous solution?

Answer 23

the ions are free to move as mobile charge carriers

Question 24

Define covalent bonding

Answer 24

the strong electrostatic attraction between a shared pair of electrons and the nuclei of the bonded atoms

Question 25

Where can covalent bonding occur?

Answer 25

between atoms in non-metallic elements compounds of non-metallic elements polyatomic ions

Question 26

Define covalent bond

Answer 26

the overlap of atomic orbitals, each containing 1 electron to give a shared pair of electrons

Question 27

Give 3 common features of a covalent bond

Answer 27

* the shared pair of electrons is attracted to the nuclei of both of the bonding atoms * the bonded atoms often have outer shells with the same electron structure as the nearest noble gas * the attraction is localised, acting solely between the shared pair of electrons and the nuclei of the two bonded atoms (forming a molecule)

Question 28

Define molecule

Answer 28

the smallest part of a covalent compound that can exist while retaining its chemical identity, consisted of two or more atoms covalently bonded together

Question 29

Define displayed formula

Answer 29

a formula showing the relative positioning of all the atoms in a molecule and the bonds between them

Question 30

Define lone pair

Answer 30

an outer shell pair of electrons that is not involved in chemical bonding

Question 31

How many covalent bonds can carbon form?

Answer 31

4

Question 32

How many covalent bonds can nitrogen form?

Answer 32

3

Question 33

How many covalent bonds can oxygen form?

Answer 33

2

Question 34

How many covalent bonds can hydrogen form?

Answer 34

1

Question 35

What is special about Boron?

Answer 35

has only 3 outer shell electrons which can be paired - showing predictions for bonding cannot be based solely on noble gas electron structure

Question 36

For elements in period 2, the n=2 outer shell can hold just 8 electrons. But what is special about phosphorous, sulfur and chlorine?

Answer 36

the n=3 outer shell can hold 18 electrons, so more electrons are available for bonding

Question 37

Give the formula for different fluorides containing phosphorous

Answer 37

PF3 | PF5

Question 38

Give the formula for different fluorides containing sulfur

Answer 38

SF2 SF4 SF6

Question 39

Give the formula for different fluorides containing chlorine

Answer 39

ClF ClF3 ClF5 ClF7

Question 40

What is significant about SF6

Answer 40

expansion of the octet where sulfur's outer shell contains more electrons than the nearest noble gas only possible from the n=3 shell when a d-sub-shell becomes available for expansion

Question 41

In a double covalent bond, the electrostatic attraction is between _ and the nuclei of the bonding atoms

Answer 41

two shared pairs of electrons

Question 42

In a triple covalent bond, the electrostatic attraction is between _ and the nuclei of the bonding atoms

Answer 42

three shared pairs of electrons

Question 43

Define dative covalent / coordinate bond

Answer 43

a shared pair of electrons in which the bonded pair has been provided by one of the bonding atoms only

Question 44

In a dative covalent bond, what would the shared electron pair have been originally?

Answer 44

a lone pair of electrons on one of the bonded atoms

Question 45

What does average bond enthalpy serve as a measurement of?

Answer 45

covalent bond strength

Question 46

The larger the value of average bond enthalpy, the _ the covalent bond.

Answer 46

stronger