3.1.1 Periodicity Flashcards
(40 cards)
1
Q
how was the periodic table arranged before
A
- elements arranged in order of atomic mass
- lines up elements in groups with similiar properties
2
Q
how is the periodic table arranged now
A
- elements arranged in order of increasing atomic number (proton)
- elements arranged in vertical columns called groups
- elements arranged in horizontal rows called periods
3
Q
what do elements in the same group have
A
- atoms with the same number of outer-shell electrons and similiar properties
4
Q
what do elements in the same period have
A
- the same number of electron shells (energy levels) or highest energy electron shells
5
Q
what are the 4 blocks in the periodic table
A
- s, p, d, f
6
Q
what is the periodic trend in electron configurations across period 2
A
- 2s sub-shell fills with 2 electrons
- 2p sub-shells fill with 6 electrons
7
Q
what is the periodic trend in electron configurations across Period 3
A
- 3s sub-shell fills with 3 electrons
- 3p sub-shells fill with 6 electrons
8
Q
what does ionisation energy measure
A
- measures how easily an atom loses electrons to form positive ions
9
Q
define first ionisation energy
A
- the energy required to remove one electron from each atom in one mole of gaseous atoms of an element to form one mole of gaseous 1+ ions
10
Q
define second ionisation energy
A
- energy required to remove one electron from each ion in one mole of gaseous 1+ ions of an element to form one mole of gaseous 2+ ions
11
Q
what are the 3 factors that affect ionisation energy
A
- atomic radius
- nuclear charge
- electron shielding
12
Q
why do successive ionisation energies increase
A
- nuclear attraction on remaining electrons increases
- the electrons are closer to nucleus + so harder to remove them
> therefore inc ionisation energy
13
Q
what is the trend in first ionisation energy down a group
A
- decreases:
> atomic radius inc
> more inner shells so shielding inc
> nuclear attraction to outer electrons dec
> first ionisation energy dec
> although nuclear charge inc, the effects are outweighed by inc atomic radius
14
Q
what is the trend in first ionisation energy across a period
A
- increases:
> nuclear charge inc (more protons in nucleus)
> same shell - similiar shielding
> nuclear attraction inc
> atomic radius dec
> first ionisation energy inc
15
Q
why is there a decrease in ionisation energy from Br to B in period 2
A
- this marks the start of filling the 2p sub-shell
- 2p sub-shell in B has higher energy than 2s sub-shell in Br
> therefore it’s easier to remove the the 2p electron in B than one of the 2s electrons in Br
16
Q
why is there a decrease in ionisation energy from N to O in period 2
A
- in N and O, the highest energy electrons are in 2p sub-shell
- in O, the paired electrons in one of the 2p orbitals repel one another
> making it easier to remove an electron from O, atom than N atom
> so first ionisation energy of O is less than that of N
17
Q
where are the two changes in first ionisation energy found going across the periods
A
- from G2-G13
- from G15-G16
18
Q
what is periodicity
A
- repeating trend in properties of elements across each period
19
Q
what do simple molecular structures consist of
A
- few atoms covalently bonded + held by weak IMF (London forces)
20
Q
what do giant covalent structures consist of
A
- billions of atoms held by strong covalent bonds to form a regular lattice
21
Q
what are some properties of simple molecules
A
- low mp/bp due to weak imf that require little energy to break
- don’t conduct electricity because no delocalised electrons or mobile charge carriers
22
Q
when melting/boiling simple molecules, what are you breaking
A
- the weak imf
23
Q
describe the solubility of giant covalent lattices
A
- insoluble in almost all solvents
- covalent bonds holding atoms together in lattice are too strong to be broken down by interaction with solvents
24
Q
when carbon forms 4 covalent bonds to other carbon atoms, what is the structure known as
A
- diamond
25
what is the shape + bond angle of carbon + silicon when all their outer shell electrons have been covalently bonded to other carbon + silicon atoms
- tetrahedral
- 109.5
26
why doesn't diamond conduct electricity
- all 4 outer shell electrons are involved in covalent bonding, none available for conducting electricity
27
what is the mp/bp like in giant covalent lattices
- high
- strong covalent bonds require lots of energy to break
28
why do graphite + graphene conduct electricity
- only 3 out of 4 outer shell electrons on each carbon atoms are involved in covalent bonding
> remaining electrons become delocalised allowing them to conduct electricity
29
what is graphene
- single layer of graphite, composed of hexagonally arranged carbon atoms linked by strong covalent bonds
30
where are metals + non-metals found in the periodic table
- metals founds on left + non-metals on right
31
what are elements that are close to the metal/non-metal divide called
- semi metals or metalloids
32
what is metallic bonding
- strong electrostatic force of attraction between cations and delocalised electrons
33
why can all metals conduct electricity
- metals lose their outer shell electrons to become cations
> the se of delocalised electrons can carry charge + therefore conduct electricity
34
describe the structure of a metal
- cations fixed in place, in a regular layer forming giant metallic lattice + surrounded by sea of delocalised electrons that are mobile
35
what are some properties of metals
- strong metallic bonds
- high electrical conductivity + heat
- high mp + bp
- malleable
- ductile
36
why do metals have high mp / bp
- high temp needed for large amount of energy needed to overcome strong electrostatic attraction between cations + electrons
37
describe the solubility of metals
- metals are not soluble due to strong electrostatic forces of attraction between cations and delocalised electrons
38
why are metals ductile and malleable
- due to the uniform structure of the layers of atoms that are the same size
> they can easily slide over each other
39
why do monatomic substances have low mp/bp
- because there are no bonds to overcome
40
describe the periodic trends in melpting points across period 2 + 3
- mp inc from G1-G14 (giant metallic structures + giant covalent structures)
> giant covalent = higher mp
- mp sharp decrease between G14-G15 (simple molecules)
- mp low from G15-G18
