electrons and bonding chp 5

Question 1

what are shells

Answer 1

-shells are regarded as energy levels
-the energy increases as the shell number increases
-the shell number or energy level number is called the principal quantum number (n)

Question 2

how many electrons are able to occupie the shell 1-4

Answer 2

Question 3

what is the formula for calculating the number of electrons in each shell

Answer 3

2n^2

Question 4

what is an atomic orbital

Answer 4

• a region around a nucleus that can hold up to 2 electrons

Question 5

what make up the shells

Answer 5

shells are made up of sub shells which themselves are made up of atomic orbitals

each new shell gains a new type of sub shell and therefore orbital

Question 6

what are the features of an s-orbital

Answer 6

-the shape of a sphere
-each shell from n=1 contains 1 s-orbital
-the greater the shell number (n), the greater the radius of its s-orbital

Question 7

what are the features of a p-orbital

Answer 7

-the electron cloud is within the shape of a dumb-bell
-one orbital can contain 1 or 2 electrons
-there are 3 separate p-orbitals at right angles to one another (these orbitals are referred to as px,py and pz
-each shell from n=2 contains 3 p-orbitals
-the greater the shell number n, the further the p-orbital is from the nucleus

Question 8

what are the features of the d and f orbtials

Answer 8

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

Question 9

what is a sub-shell

Answer 9

• orbitals of the same type are grouped together as sub-shells to produce shells

Question 10

table

how does the presence of sub-shells effect the number of electrons within a shell

Answer 10

Question 11

how do orbtials fill

Answer 11

orbitals fill in order of increasing energy

Question 12

why do electrons in the same orbitals spin oppositly to eachother

Answer 12

• helps to mitigate the repulsion between the like charges, within an orbital

Question 13

How are orbitals of the same energy filled

Answer 13

-within a sub-shell, one electron occupies each orbital before pairing up starts, this prevents any repulsion between paired electrons until there is no further orbital available at the same energy level

Question 14

what does the electron configuration show

Answer 14

shows how sub-shells are occupied by electrons

Question 15

how would you write a shorthand configuration

Answer 15

the short hand is shown in terms of the previous noble gas plus the outer electron sub-shells of the element your illustrating

Question 16

what do the blocks of the peridoic table tell us

Answer 16

s-block, highest energy electrons in the s-sub-shell
P-block, highest energy electrons found in the p-sub-shell
D-block, highest energy electrons in the d-sub-shell

Question 17

how does ionisation effect the electron configuration

Answer 17

the highest energy sub-shells lose or gain electrons

Question 18

whats unique about the 4s and 3d sub-shells

Answer 18

• 4s sub-shells fill and empty before filling and emptying of 3d sub-shelled
• as is at a lower energy level

Question 19

what is ionic bonding

Answer 19

• electrostatic attraction between positive and negative ions

Question 20

describe how to produce a dot and cross diagram for a ionic compound

Answer 20

• electrons from the oxidising atoms are shown as either cross or dots
• Show the outer shell of both ions with the electrons
• use square brackets to show charge is over whole ion
• show the charge of the ion just outside square brackets

Question 21

what is the structure of an ionic compound and what causes this

Answer 21

ionic compounds form giant ionic lattices due to the fact that an ion attracts oppositely charged ions in all directions

Question 22

what is the boiling and melting point of ionic lattices and how is it explained

Answer 22

-Almost all ionic compounds are solid and room temperature
-High temperatures are needed to provide the energy needed to overcome the electrostatic forces, therefore most ionic compounds have high melting and boiling points.

Question 23

how does the individual charge of an ion effect the ionic compounds melitng and boling point

Answer 23

the melting points are higher for lattices containing ions with greater ionic charges, as there is stronger attraction between ions

Question 24

Are ionic compounds soluble

Answer 24

many ionic compounds dissolve in polar solvents, such as water, by breaking down the lattice and surrounding each ion.

Question 25

how does the charge of individual ions in the ionic compound effect the solubility of the ionic compound

Answer 25

in a compound made of ions with larger charges, the ionic attraction may be too strong for water to be able to break down the lattice structure and therefore the compound will not be very soluble

Question 26

Are ionic compounds electrically conductive

Answer 26

in the solid state, an ionic compound does not conduct electricity, but once melted or dissolved in water the ionic compound does conduct electricity.

Question 27

what explains an ionic compounds properties of electrical conductivity

Answer 27

• when solid no mobile charge carries to carry the charge, so not conductive
• once molten/dissolved, ions within compound no longer fixed, become mobile charge carries and can conduct electricity

Question 28

what is a summary of the properties of ionic compounds

Answer 28

• high melting and boiling points
• dissolve in polar solvents
• conduct electricity when liquid or dissolved
• typically form ionic lattices

Question 29

what is covalent bonding

Answer 29

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

Question 30

when does covalent bonding occur

Answer 30

• atoms in non-metallic elements (h2 & O2),
• compounds of non metallic elements (H2O & CO2)
• polyatomic ions (NH4+).

Question 31

in which structures are covalent bonds found

Answer 31

a small covalent molecule (H2), a giant covalent structure (SiO2) or a charged polyatomic ion (NH4+)

Question 32

what actually is a covalent bond

Answer 32

-A covalent bond is the overlap of atomic orbitals, each containing one electron, to give a shared pair of electrons
-The shared pair of electrons is attracted to the nuclei of both the bonding atoms

Question 33

How is the charge distributed in a covalent bond

Answer 33

the attraction is localised, acting solely between the shared pair of electrons and the nuclei of the 2 bonded atoms.

Question 34

Describe what a dot and cross diagram looks like for a covalent bond

Answer 34

use dots and crosses to show electrons so that we can determine the origin of each electron.
electrons are shared not transferred

Question 35

what is a displayed formula

Answer 35

-a displayed formula shows the relative positing of atoms and the bond between them as lines
-paired electrons that are not shared are called lone pairs, these can also be added to a displayed formulae

Question 36

how many covalent bonds can carbon, nitrogen, oxygen and hydrogen make

Answer 36

-carbon forms 4 bonds
-nitrogen forms 3 bonds
-oxygen forms 2 bonds
-hydrogen forms 1 bond

Question 37

how do elements with access to a n=3 shell differ when bonding

Answer 37

the n=3 outer shell can hold 18 electrons, so more electrons are available for bonding, this can realist in different bonding arrangements for elements such as sulfur with 6 electrons in its outer shell

Question 38

What is a dative covalent bond

Answer 38

A dative covalent bond is a covalent bond in which a shared pair of electrons has been supplied by only 1 of the bonding atoms.

Question 39

what is an example of a molecule that contains a dative covalent bond

Answer 39

An ammonia ion contains a dative covalent bond

Question 40

Name a compound/molecule that contains a triple covalent bond

Answer 40

triple covalent bonds form between nitrogen molecules in diatomic nitrogen molecules and between the carbon and nitrogen atoms in a molecules of hydrogen cyanide

Question 41

Name a compound that contains a double covalent bond

Answer 41

double bonds exist between oxygen atoms within diatomic oxygen molecules and also between the carbon and oxygen in a carbon dioxide molecule

Question 42

define average bond enthalpy

Answer 42

• average amount of energy required to break a particular type of covalent bond in a molecule