3.1.1 periodicity Flashcards
1
Q
How was the old period table arranged?
A
- Mendeleev ordered the first 60 elements in increasing atomic number
- left gaps for unknown elements and swapped elements that didnt have fitting properties
- he also organised the elements in groups of similar properties
2
Q
How is the period table arranged now?
A
- It is now organised in seven periods and 18 vertical groups
- ordered in increasing atomic number
3
Q
What do elements in the same group contain?
A
- the same number of electrons in their highest energy electron shell
- all have similar properties
4
Q
What do elements in the same period have in common?
A
- The number of the highest energy electron shell in an elements atoms
5
Q
to do with electronic configuration
What is the trend across a period?
A
- each period starts with a new higher energy level
- for example, period 2 starts with 2s then p and period 3 starts with 3s and fills into the p shell
6
Q
How are elements divided into blocks?
A
- elements can be divided into s,p,d and f blocks
- the blocks represent the shell their outer electrons are located in
7
Q
What is ionisation energy?
A
Ionisation energy is the measure of how easily an atom loses an electron to form ions
8
Q
What is the definition of 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 plus ions
9
Q
Write an eqaution for 1st ionisation energy of Helium?
A
He (g) - He+ + e-
10
Q
What is the definition of 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
11
Q
What factors affect nuclear attraction and therefore ionisation energy?
A
- atomic radius
- nuclear charge
- sheilding
12
Q
How does atomic radius affect ionisation energy?
A
- The grester the distance between the nucleus and the outer electrons, the less the nuclear attraction
- this means that ionisation energy decreases
13
Q
How does nuclear charge affect ionisation energy?
A
- the greater the nuclear charge, the more protons in the nucleus of an atom
- this increases the attraction between the nucleus and outer electrons
- the greater the nuclear charge, the greater the ionisation energy
14
Q
How does sheilding affect ionisation energy?
A
-The shielding effect is the repulsion between the inner electrons and outer electrons, reducing the attraction between the nucleus and outer electron
- this reduces ionisation energy
15
Q
The second ionisation energy of helium is greater than the first ionisation energy.
Explain why.
A
- the second ionisation energy of helium is greater than the first as in a helium atom there are two protons attracting two electrons
- after the first ionisation energy, there are 2 protons attracting one electron
- ## This increases the nuclear charge therefore increasion the attraction between the outer electron and nucleus so more ionisation energy is needed to remove the second electrons
16
Q
What is the trend in ionisation energy across a period?
A
- first ionisation energy increases due to a decreasing atomic radius, increasing nuclear charge which increases nuclear attraction
17
Q
What is the trend in ionisation energy down a group?
A
- ionisation energy decreases down a group
- This is because atomic radius increases, shielding increases due to more inner shells
- this decreases the nuclear atrraction on the outer electrons
18
Q
What are the exceptions across period 2?
A
- there is a increase from lithium to beryllium, a fall from beryllium to boron
- A rise from boron to carbon to nitrogen
- there is then a fall to oxygen and a rise to flourine and neon
19
Q
Why is there a fall from beryllium to boron?
A
- beryillium has an electronic configuration of 1s2, 2s2 howeber boron has an electronic configuration of 1s2 2s2 2p1
- this means that the outer electron in the p sub shell is easier to remove as it is in a higher energy sub shell, reducing its nuclear attraction
20
Q
Why is there a fall in ionisation energy from nitrogen from oxygen?
A
- in nitrogen, each electron in the p sub shell is in a different orbital however in oxygen there is an orbital that contains two electrons
- these two electrons repel eachother which makes it easier to remove an electron from an oxygen atom
- this reduces ionisation energy
21
Q
What are the exceptions across period 3?
A
-There is a fall from magnesium to Aluminium
- There is a fall from phosphorus to sulfur
22
Q
Why is there a fall from magnesium to aluminium?
A
- Aluminiums electronic configuration is 1s2 2s2 2p6 3s2 however magnesiums electronic configurstion is 1s2 2s2 2p6 3s2 3p1
- this means in aluminium, the distance from the nucleus and outer electron increases, increasing shielding
- this means it is easier to remove an electron from aluminium
23
Q
Why is there a fall in ionisation energy from phosphorous to sulfur?
A
- sulphur contains two electrons in an orbital, repelling eachother
- this reduces the ionisation energy of sulfur
24
Q
What is metallic bonding?
A
- metallic bonding is the strong electrostatic attraction between cations and delocalised electrons
25
What are the properties of metals?
- solid at room temp exempting mecury
- good conducters of electricity and heat
-
26
Why do metals have these properties?
- the electrostatic attraction between the cations and delocalised electrons requires a lot of energy to overcome
- metals conduct electricity as it contains delocalised electrons that can carry charges
27
Why are metals insouble?
- although metals are polar, any interaction between metals and solvents would lead to a reaction and not dissolving
28
What are the two structures non metallic elements make?
- simple molecular compounds
- Giant covalent structures
29
How are simple molecular compounds held together and what are the properties?
- weak intermolecular forces
- this causes them to have low melting and boiling points
30
How are giant covalent structures held together and what are the properties?
- held by billions of atoms with a network of strong covalent bonds which form a giant covalent lattice
- have high melting and boiling points
- insouble in all solvents
- non - condutors of electricity with some exceptions
31
What giant covalent structures can conduct electricity?
-graphene and graphite which are forms of carbon
32
What is the structure of graphite?
- each carbon atom forms three covalent bonds with three other carbon atoms
- organised into sheets of hexagons, these sheets are arranged in layers and are joined by weak intermolecular forces called van der waals
33
What are properties of graphite?
- soft, slipperly due to its layers that easily slide
- high melting and boiling point
- insouble in both water and organic solvents
- good conductor of electricity
- low density
34
Why does graphite have these properties?
- delocalised electron which are free to move between the sheets in graphite (good conductor)
- high melting and boiling points due to its giant covalent structure and strength of covalent bonds
- insouble in water and organic solvents due the covalent bonds and the attraction between carbon atoms
- low density due to distance between layers as they are held apart by weak intermolecular forces (van der waals)
35
What is the structure of graphene?
- Graphene is a single layer of graphite which is composed of hexagonal arranged carbon atoms held by strong covalent bonds
36
What are the properties of graphene?
- high melting and boiling point
- conductor due to the delocalised electron
- flexible and strong
37
What is the trend in melting point across period 2?
- There is an increase from lithium to carbon, then there is a sharp decrease from carbon to nitrogen
- From nitrogen to neon, it remains constantly low
38
Why is there an increase in melting point from lithium to carbon?
- This is because lithium and beryllium are giant metallic structures and boron and carbon are giant covalent structures meaning a lot of energy is required to overcome the bonds
39
Why is there a decrease in melting point from carbon to nitrogen?
Nitrogen to neon are simple molecular structures held by weak London forces meaning they have low melting points
40
What is the trend in melting point across period 3?
- there is an increase from sodium to silicon
- there is a decrease in melting point for, silicon to argon
41
Why does the melting point across period three increase from sodium to silicon?
- There is an increase from sodium to aluminium as they are giant metallic structures
- There is a greater increase to silicon as silicon is a giant covalent structure
42
Why is there a decrease in melting point from silicon to argon?
- Phosphorus to argon are simple molecular structures held by weak London forces meaning they require little energy to overcome its bonds
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