Chapter 5 - Electrons and Bonding

Question 1

how many electrons fill shell number 1?

Answer 1

2

Question 2

how many electrons fill shell number 2?

Answer 2

8

Question 3

how many electrons fill shell number 3?

Answer 3

18

Question 4

how many electrons fill shell number 4?

Answer 4

32

Question 5

what are shells?

Answer 5

• shells are regarded as energy levels
• the energy increases as the shell number increses
• the shell number/energy level number is called the principal quantum number

Question 6

what is an atomic orbital?

Answer 6

a reigon around the nucleus where there is a high probability of finding an electron

Question 7

what are the properties of orbitals?

Answer 7

• an orbital can hold one or two electrons but no more
• there are different types of orbitals
• each type of orbital has a different shape

Question 8

what are the different types of orbitals?

Answer 8

s-, p-, d- and f- orbitals

Question 9

what are the properties of s- orbitals?

Answer 9

• sphere shaped
• each shell from n=1 contains 1 s-orbital
• radius increases with shell number

Question 10

what are the properties of p- orbitals?

Answer 10

• dumb-bell shaped
• there are 3 at right angles to eachother
• each shell from n=2 contains 3 p- orbitals
• distance from nucleus increases with shell number

Question 11

what are the properties of d- and f- orbitals?

Answer 11

• each shell from n=3 contains 5 d- orbitals
• each shell from n=4 contains 7 f- orbitals

Question 12

what sub-shells are present in shell 1?

Answer 12

1s

Question 13

what sub-shells are present in shell 2?

Answer 13

2s and 2p

Question 14

what sub-shells are present in shell 3?

Answer 14

3s, 3p and 3d

Question 15

what sub-shells are present in shell 4?

Answer 15

4s, 4p, 4d and 4f

Question 16

in which order do orbitals fill?

Answer 16

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d, 4f

Question 17

how are electrons drawn in the electrons-in-box model?

Answer 17

as two arrows, one up and one down as they have opposite spins

Question 18

why do electrons have opposite spins?

Answer 18

the opposite spins help counteract the repulsion between the negative charges of the electrons

Question 19

how would 4 electrons occupy the p-orbitals?

Answer 19

2 in the first sub shell, 1 in the second sub shell and 1 in the last sub shell as electrons repel each other

Question 20

how do you express electron configuration in short hand?

Answer 20

previous noble gas + outer electron sub shells

Question 21

when are cations formed?

Answer 21

when atoms lose electrons (positive ions)

Question 22

when are anions formed?

Answer 22

when atoms gain electrons (negative ions)

Question 23

which shell empties first when electrons are lost: 4s or 3d?

Answer 23

4s empties before 3d
(first in, first out)

Question 24

what is a dot-and-cross diagram in ionic bonding??

Answer 24

• electrons are shown as dots or crosses
• outer shell electrons from one atom are transferred to another
• positive and negative ions are formed with a full outer shell

Question 25

what is the stucture of an ionic compound and why?

Answer 25

ions attract oppositely charged ions in all directions, so a giant ionic lattice of positive and negative ions where each ion is surrounded by oppositely charged ions is formed

Question 26

what is the trend in melting and boiling points of ionic compounds?

Answer 26

- almost all are solid at room temp as there is insufficient energy to overcome the strong electrostatic forces of attraction between the oppositely charged ions - high temperatures are needed to overcome the attraction so melting and boiling points are high

Question 27

what is the trend in solubility of ionic compounds?

Answer 27

- ionic compounds dissolve in polar solvents (e.g water) - polar molecules break down the lattice and surround each ion in solution - in a compound with ions of large charges ionic attraction may be too strong for water to break down the lattice structure so the compound wont be very soluble

Question 28

what is the trend in electrical conductivity of ionic compounds?

Answer 28

- when solid ions are in a fixed position in the lattice and there are no mobile charge carriers so the compound will not conduct electricity - when liquid or dissolved the lattice breaks down so ions can move as mobile charge carriers so the compound will conduct electricity

Question 29

what is ionic bonding?

Answer 29

the electrostatic attraction between positive and negative ions in an ionic compound

Question 30

what is covalent bonding?

Answer 30

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

Question 31

what does covalent bonding occur between?

Answer 31

non-metallic elements, compounds of non-metallic elements and polyatomic ions

Question 32

what does ionic bonding occur between?

Answer 32

cations and anions

Question 33

what is a covalent bond?

Answer 33

the overlap of atomic orbitals where - the shared pair of electrons is attracted to both nuclei - the bonded atoms often have outer shells with the same electron structure as the nearest noble gas

Question 34

what is the stucture of a covalent compound and why?

Answer 34

the attraction is localised, acting solely between the shared pair of electrons and the nuclei of the two bonded atoms. this means a small unit called a molecule (the smallest part of a covalent compound) is formed

Question 35

what is the displayed formula of a covalent compound?

Answer 35

- a displayed formula shows the relative positioning of atoms and the bonds between them as lines - lone pairs are added as dots

Question 36

how many covalent bonds does carbon form?

Answer 36

4

Question 37

how many covalent bonds does nitrogen form?

Answer 37

3

Question 38

how many covalent bonds does oxygen form?

Answer 38

2

Question 39

how many covalent bonds does hydrogen form?

Answer 39

1

Question 40

how many covalent bonds does boron form?

Answer 40

boron forms covalent compounds in which its 3 outer shell electrons are paired, so sometimes only has six electrons around the boron atom

Question 41

what is expansion of the octet?

Answer 41

covalent compounds with more than 8 electrons in the outer shell

Question 42

when is expansion of the octet possible?

Answer 42

from the n=3 shell, when more than 8 electrons can be held in the outer shell

Question 43

what is a double bond?

Answer 43

when the electrostatic attraction is between two shared pairs of electrons and the nuclei of the bonded atoms (e.g O2 and CO2)

Question 44

what is a triple bond?

Answer 44

when the electrostatic attraction is between three shared pairs of electrons and the nuclei of the bonded atoms (e.g N2)

Question 45

what is a dative covalent bond?

Answer 45

a covalent bond in which the shared pair of electrons has been supplied by one of the bonding atoms only. the shared pair was originally a lone pair of electrons on one of the bonded atoms

Question 46

what is average bond enthalpy?

Answer 46

a measurement of covalent bond strength