Topic 2 Atomic Theory SL+HL

Topic 2.1 The atom Position ChargeRelative Mass Proton; p + Nucleus 1+ 1 Neutron; n Nucleus 0 1 Electron; e - Cloud/orbitals 1- 5*10 -4 around the ~ 0 nucleus Subatomic particles

An atom has no net charge. Atomic ions have lost or gained electrons and have a charge The number of Protons in an atom  The Element  Atomic number  Z  Number of Electrons

Isotopes Atoms with same number of Protons but different number of Neutrons are isotopes They are the same element = same Atomic number = Z Isotopes have different mass numbers Mass number = A = no. of protons + no. of neutrons The chemical properties is the same The physical properties can differ a little

The Symbol for Isotopes/Atoms

+ - Nucleus Electron H 1 Atomic number 1 Mass number Isotopes of hydrogen Natural abundance 99,99 %

+ - Electron H 1 2 Isotopes of hydrogen- Deuterium Nucleus Mass number Atomic number Heavy water- D 2 O natural abundance 0,01 %

+ - Electron H 1 3 Isotopes of hydrogen- Tritium Nucleus Mass number Atomic number Radioactive

- Alpha radiation + + Beta radiation Gamma radiation He -- e-e-  Radioactivity

Halflife Radiation intensity t ½ = 1600 år Ra Rn  Radium-226 Radon-222 alfaparticlegammaradiation He 2 4

Radioisotopes Not stable isotopes 14 Carbon C less than 0.001% of carbon, half life 5730 years. 14 C  14 N + e - 14 N + cosmic radiation  14 C. Since the cosmic radiation is the same over time, the concentration of 14 C as Carbon dioxide will be the same in the air over time. There will be a fixed ratio between 12 C and 14 C. The plants take up CO 2 with the ratio. But when the plant die the ratio will be changed when the amount of 14 C decreases due to radioactive decay. By looking at the ratio and knowing the half-life is it possible to determine the age of an object. It accurate to about year old material.

60 Co Penetrating power to treat cancerous cells Gamma (  ) radiation emitter Been used more than 50 years for different cancer forms. Also to stop the immune system to attack transplanted organs.

131 I Half-life of 8 days Beta (  ) and Gamma (  ) emitter Thyroid cancer Diagnose if thyroid gland functions normally

125 I Half-life of 60 days Prostate cancer and brain tumour

Topic 2.2 The mass spectrometer How to measure atomic masses.

1.The sample is Vaporised in vacuum. 2. The sample is Ionised in an electron beam. A + e -  A + + 2e The ions are Accelerated in an electric field into a long tube.

4. The ions are Deflected (= change of flight way) in a magnetic field. 5. Depending of the ions mass and the magnetic field some ion will deflect into a Detector. The number of ion that hit the detector is proportional to the signal from the detector. By changing the power of the magnetic field different ions can be detected.

A mass spectrometer can be used to determine the natural abundance of isotopes. The mass spectrum of Magnesium

The most abundant isotope is set to be 100. The other ones as in proportion to this. Calculating the natural abundance: = Mg =100/127.2 = 78.6% 25 Mg = 12.8/127.2 = 10.0% 26 Mg = 14.4/127.2 = 11.3% 24* * *0.113 = 24.3 (g/mol)

Topic 2.3 Electron arrangement Electromagnetic spectrum Electromagnetic radiation has been very important in the studies of the atom There are different types of electromagnetic radiation: Gamma rays, X-rays, UV, Visible light, IR, Microwaves, Radio waves. They differ in Wavelength. From m to 10 4 m The relation between Wavelength, L(m)and Frequency, n (s -1,Hertz) Ln = cc =speed of light, 3*10 8 m/s Shorter wavelength => Higher frequency =>more energy.

Continuous spectrum

Line spectrum.

+ + Atomíc nucleus K L M Electron shells

Absorptions spectra: energy needed to move an electron to a higher shell. Emission spectra: energy released when the electron falls back to the lower shell. The color of the light show the energy difference between the two shells

The line spectrum of the hydrogen atom- Balmer series Named after Johann Balmer, who discovered theJohann Balmer Balmer formula, an empirical equation to predictempirical the Balmer series, in Balmer lines are historically referred to as "H-alpha", "H-beta",H-alpha "H-gamma" and so on, where H is the element hydrogen. Four of the Balmer lines are in the technically "visible" part of the spectrum, with wavelengths longer than 400 nm. Parts of the Balmer series can be seen in the solar spectrum.solar spectrum H-alpha is an important line used in astronomy to detect the presence of hydrogen. The longest jump between two neighboring shells is K  L (n=1  n=2) Line converge in the higher frequency end due to many similar energy transitions, and ionisation of the electron

Electron arrangement of atoms in terms of main energy levels (Shells) Main Energy levelMax Number of e - If valence e - K12 2 L28 8 M318 8 Valence electrons: The electron in the highest main energy level

+ - Electron Hydrogen atom, H 1 p+ K-shell + - Helium atom, He 2 p e Litiumatom, L i 3 p e - K-shell L-shell Berylliumatom, Be 4 p e

+ - B 5 p e - K-shell L-shell Carbon, C 6 p e Nitrogen, N 7 p e Oxygen, O 8 p e Fluor, F 9 p e Neon, Ne 10 p e

ElementAtomic numberKLMN H11 He22 Li321 Be422 B523 C624 N725 O826 Electron arrangement for elements 1-8

Electron arrangement for elements 9-20 ElementAtomic numberKLMN F927 Ne1028 Na11281 Mg12282 Al13283 Si14284 P15285 S16286 Cl17287 Ar18288 K Ca202882