2A The Atom And Redox Flashcards
What is an isotope
Atoms with the same element with different number of neutrons and different masses but the same number of protons and electrons
What are chemical reactions and physical properties like for isotopes of the same element?
Chemical reactions are based off of the amount of electrons that an atom has therefore an isotope will have no difference in chemical reactions
However physical properties may be slightly different: eg, higher mass isotopes have higher MP, BP, density
What is an ion
A charged atom with a different number of electrons to protons
Relative Isotopic mass
The mass of an atom of an isotope compared to 1/12th of the mass of a Carbon 12 atom
Relative Atomic Mass
The weighted mean mass of an atom of an element compared with 1/12th of the mass of an atom of carbon 12
Relative Atomic mass equation
(Abundance x mass) + (Abundance x mass) / 100 = Ar in gaol-1
How is the % abundance of the isotopes in an element found
A mass spectrometer
How does the mass spectrometer work
- Gaseous particles are fired into the spectrometer and ionised to form positive ions
-Hit with a high beam of electrons
X(g) + e- -> X+(g) + 2e- - The ions are accelerated, heavier ions move slower and lighter ions move faster forming a mass spectrum detected as a mass to charge ratio.
- m/z relative mass of an ion / relative charge of an ion
For an ion with 1 positive charge, what is the mass to charge ratio.
Ratio is equivalent to the relative isotopic mass
Relative molecular mass (Mr)
Weighted mean mass of a molecule compared with 1/12th the mass of a carbon 12 atom
Relative formula mass
- Used for giant ionic structures
- The sum of the Ar of the compound in the giant ionic lattice
What is ionisation energy
How easily an atom loses electrons to form positive ions
What is 1st ionisation energy
The amount of energy it requires to remove 1 electron from atom in one mole of gaseous atoms of an electron to make one mole of gaseous 1+ ions
X(g) -> X+ + e-
Factors affecting ionisation energy
-Nuclear Charge
-Atomic radius
-Shielding
How many ionisation energies does an element have
As many as the number of electrons there are
The Second ionisation energy
The amount of energy required to remove 1 electron from one mole of gaseous +1 ions to form one mole of gaseous +2 ions
Why is the second ionisation energy larger than the first ionisation energy
Because when the first electron is removed the atomic radius gets slightly smaller and therefore the nuclear attraction gets larger
Ionisation energy down a group
Despite the nuclear charge increasing down a group, the atomic radius and shielding also increases due to the extra full shell of electrons and therefore the nuclear attraction decreases and so the first ionisation energy decreases
Ionisation energy across a period
As you go across the nuclear charge gets larger, but the atomic radius decreases and the shielding remains roughly the same therefore the nuclear attraction increases and therefore as you go across the ionisation energy increases
What are shells made up of
Sub shells
What are sub shells made up of
Orbitals
What are the orbitals, their shapes and how many types of each?
S- spherical, one type of S orbital
P - Dumb bell, three types of P orbitals, Px, Py and Pz
D - 5 types of D orbitals
How many electrons max in each orbital
S - 2 electrons
P - 6 electrons
D - 10 electrons
What does degenerate mean in terms of orbitals and why is this important
‘Of identical identity’ - When a sub-shell contains many degenerate orbitals - there is always one electron in each orbital before filling with the second electron (Hund’s rule)
In Which order do the sub shells fill up
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 4d
What are the exceptions to Huns rule
Cu: 1s2, 2s2, 2p6, 3s2, 3p6, 3d10, 4s1 -> 4s half full, 3d complete
Cr: 1s2, 2s2, 2p4, 3s2, 3p6, 3d5, 4s1 -> both 4s and 3d half full
Why does 1st ionisation energy dip in Group 3
Eg the outer election in Al is in a higher sub-shell than Mg and it requires less energy to remove an electron from a higher energy sub-shell
Why is their a dip in 1st ionisation energy at group 6
Eg: P has a half full outer subshells whereas S has one paired electron with negative spins they repel each other and therefore requires less energy to remove
What is oxidation
The loss of electrons
What is reduction
The gain of electrons
What is an oxidising agent
The species responsible for oxidising another species, it contains the element being reduced
What is a reducing agent
A species responsible for reducing another element - containing the element being oxidised
Oxidation number rules :
Atoms of an uncombined element have an oxidation number of…
0
Oxidation number rules:
Atoms of group one elements have an oxidation number of…
+1
Oxidation number rules:
Oxidation number of atoms of group 2 elements is…
+2
Oxidation number rules:
Atoms of the element Fluorine have the oxidation number…
-1
Oxidation number rules:
Atoms of Oxygen element have an oxidation number of…
(And exceptions?)
-2
Except when in peroxide then it is -1
Oxidation number rules:
Hydrogen atoms have an oxidation number of…
(Exceptions)
+1
Except in a hydride then it is -1
Oxidation number rules:
Simple ion oxidation number =
Charge of ion
Oxidation number rules:
Compound ion oxidation numbers =
Charge of ion
Oxidation number rules:
Neutral compound oxidation number =
0
If the oxidation number increases
Then the substance has been oxidised
If oxidation number decreases
Substance has been reduced
