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Atom that has an unstable nucleus and emits radiation(α, β, γ rays) during its decay to a more stable form.

Carbon-14: Determine age of artifacts

Cobalt-60: Kill cancer cells

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IF for %, z= 100.

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Line Spectrum (V)I(B)GYO(R) after B is light blue.

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1st ionisation energy → low

2nd ionisation energy → abit high

3rd ionisation energy → high

4th ionisation energy → extremely high!

Group of element? 3rd.

Why? 4e- is not from valence shell.

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Be-B , Mg-Al

B and Al lower in graph because :

valence e- is in 2p (has higher energy level, thus further from nucleus)

↑ dist. , ↓attraction and ionisation energy

screened by 1s^2 and 2s^2 electrons

N-O , P-S
O and S lower in graph because:

4th e- of O & S has to pair up with an e- in a box(orbital diagram), →repulsion→easier to remove

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Energy required to remove the most loosely held electrons from 1mol of gaseous atoms ---> ions with a charge of 1+.

Symbol (g) is IMPORTANT! ...when writing eq.

Factors affecting the size of ionisation energy

Charge of nucleus

Distance of electron from the nucleus

No. of electrons between outer electrons and nucleus (screening/shielding)

Electron alone/paired (paired are removed more easily due to repulsion from each other)

Patterns in P2 & P3
Across P2&P3, no. of p+ ↑, outer electrons move closer to nucleus, thus ionisation energy ↑

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Electrons gain energy→jump to another shell

When excited, e- are unstable.

When e- loses energy, it returns to ground state(more stable).

Number of electrons in a shell - 2n^2

Given choice, electrons would not share the same space, takes less energy to occupy next space.

At n=8,9,10, the amount of energy released to come back to n=2, is the same, there is no increase, there it is the same amount of energy required to overcome the attraction force of the nucleus (first ionization energy).

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Aufbau - Place e- starting at lowest energy

Hund's - In the 2p orbitals, 2px 2py 2pz (each of the boxes) must each contain a single e- before 2px 2py 2pz will have a second e-.

Pauli Exclusion Principle - electrons must have opposite spin.

Cu & Cr are EXCEPTIONS (arrow from 4s^2 goes to 3d

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Emission spectra is released when photons(blast of energy released) are emitted from excited electrons as it jumps to a lower energy level.

Continuous spectrum - A spectrum with all colours/frequencies of EM radiation.

VS

Line spectrum - A spectrum with certain colours pertaining to a few frequencies.

Evidence that electron shells exist in discrete energy level and converge at higher energies - line spectra

R'ship between f, λ, colour and energy - refer to drawn notes.

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RAM - Weighted average of the masses of the isotopes when comparing it to C-12.

Calculate RAM - m/z (photo below)

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Orbitals - Regions of space where there is a high probability of finding an electron.

Main energy levels - n=1,2,3,4,5,6,

Sub levels - s(1), p(3), d(5), f(7)

EC - 1s^2 2s^2 2p^6 3s^2 3p^6 4s^2 3d^1

Lewis dot diagram :

+[Al]++

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Neutrons, Protons, Electrons

N & P+ in nucleus, E- in shell

Atomic number (proton number) - No of p+ in the nucleus of an atom

Mass number (nucleon number) - No of p+ and n in the nucleus of an atom
Isotope - Diff atoms of the same element that have the same no. of p+ but diff no of n in the nucleus of the atom.