Unit 1-2 Flashcards
(48 cards)
What is an orbital?
Region of space where there is a 95% chance of finding an electron
S,P,D and F
What is an orbit/shell/energy level?
The path of an electron around the nucleus
What shape are s and d orbitals respectively?
Spherical and dumbbell shaped
What is a charge cloud?
The orbital can be regarded as a spread of charge since the electron is likely to be anywhere in the orbital
Note: Greatest electron density is at the center
Orbitals can hold 2 electrons each. How many orbitals do each sub-shell have?
s sub-shell has 1 s-orbital
p sub-shell has 3 p-orbitals
d sub-shell has 5 d-orbitals
f sub-shell has 7 f-orbitals
What is exceptional about the 4s sub-shell?
It has a lower energy level than the 3d sub-shell and is filled first
What is an excited state?
Atoms with one or more excited electrons are in this state
What is the Aufbau principle?
Electrons in ground state occupy orbitals in order of orbital levels with the lowest being filled first
Note: 4s has a lower energy level than 3d and is filled first
What is the The Pauli exclusion principle?
Each orbital can hold 2 electrons which must have opposite spins
2 parallel spins is not allowed
What is Hund’s rule?
Each orbital of the same energy level must be occupied singly with parallel spin before pairing can take place
Why are chromium and copper exceptional in terms of electronic configuration
Its more stable to have a ½ full or full 3d sub-shell than to have a full 4s sub-shell and a 3d sub-shell with an empty orbital
As a result only 1 electron is given to the 4s sub-shell
Cr (Z = 24): [Ar]18 4s^1 3d^5
Cu (Z = 29) [Ar]18 4s^1 3d^10
Why are noble gases used for noble gas cores?
Only works using noble gases due to their full outer shells
What is the molar first ionisation energy (1st I.E)?
Energy required to remove one mole of electrons from 1 mole of gaseous atoms to form one mole of gaseous positively charged ions
What factors effect the ionisation energy of an atom?
How close the electron is to the nucleus
Weaker attraction force therefore less effective nuclear charge
Shielding
Filled inner shells weaken the attraction force, more shielding results in less effective nuclear charge
Spin pair repulsion
Paired e- are slightly easier to remove because they are repelled by their pair
What is nuclear charge?
Total positive charge of all the protons in a nucleus of an atom
What is effective nuclear charge?
The nuclear charge an outer shell electron experiences
What happens to the 1st I.E across the periodic table?
Generally increases across a row due to more protons for the same shielding, therefore increase in nuclear charge
Slight decreases occur to due shielding and spin pair repulsion
Note: Noble gases have the highest 1st I.E for their period
What happens to the 1st I.E down the periodic table?
Generally decreases down a group due to less effective nuclear charge from an increase in shielding
Note: Alkali metals have the lowest 1st I.E for their period
What is the trend for successive ionisation energies?
Increases by the 1st I.E for every successive ionisation until a new sub-shell or shell is reached, where I.E will increase slightly or significantly respectively
Note: Large increases in I.E are used to find the group of an unknown element; silicon’s 5th I.E requires far more energy than the first 4 as there’s less shielding in a new shell. Silicon is therefore in group 4
What is radioactive decay?
Protons, neutrons and electrons flying out when the original unstable nucleus divides
What happens to DNA if it is ionised by radioactive decay?
the instructions on how to live become confused, cells may turn cancerous and multiply uncontrollably
What are the qualities of alpha (α) radiation? (7)
- Slow
- Positively charged particles (2+)
- Mass of 4 and 2 units of positive charge (Helium nucleus)
- Powerful ionising effect
- Absorbed by thin paper
- Can’t enter or escape the body
- Slightly attracted towards the negative side of an electrical field
What are the qualities of beta (β) radiation? (8)
- Fast (velocities near the speed of light)
- Negatively charged electron
- Negligible mass
- Stopped by aluminium
- Can enter to skin to ionise cells
- 1/20 as ionising as alpha because of small mass and great kinetic energy
- Formed when a neutron changes to be a proton
- Highly attracted towards the positive side of an electrical field
What are the qualities of gamma (γ) radiation? (10)
- Speed of light
- Electromagnetic radiations
- Negligible mass
- Very penetrating
- Only stopped by thick lead
- Not very ionising
- Atoms gain a lot of energy upon absorbing, causing emission of other particles, which can be dangerous if it happens in a bodily cell
- Emitted in conjunction with alpha or beta
- Used as a means of removing excess energy from an excited nucleus
- Unaffected by electrical field
