Structure of atomic
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All matter is composed of atoms. Atoms are composed of protons, neutrons, and electrons. Rutherford's gold foil experiment disproved the plum pudding model of the atom and led to the discovery of the nuclear atom, with a small, dense nucleus surrounded by electrons. Niels Bohr refined this model by suggesting that electrons orbit the nucleus in discrete energy levels. When electrons change orbits, electromagnetic radiation is emitted or absorbed at wavelengths specific to each element.
Structure of atomic
- 2. AllAll mattermatter is composed ofis composed of atomsatoms.. Understanding the structure of atoms isUnderstanding the structure of atoms is critical to understanding the properties ofcritical to understanding the properties of matter.matter.
- 3. Atomic StructureAtomic Structure Neutral atomsNeutral atoms have the same number ofhave the same number of protons and electrons.protons and electrons. IonsIons are charged atoms.are charged atoms. --cationscations – have more protons than– have more protons than electrons and are positively charged.electrons and are positively charged. --anionsanions – have more electrons than– have more electrons than protons and are negatively charged.protons and are negatively charged.
- 4. HISTORY OF THE ATOMHISTORY OF THE ATOM John Dalton suggested that all matter was made up of tiny spheres that were able to bounce around with perfect elasticity and called them ATOMSATOMS
- 5. 8 X2Y16 X 8 Y+ DALTONS ATOMIC THEORY
- 6. Subatomic ParticlesSubatomic Particles Particle Mass (g) Charge (Coulombs) Charge (units) Electron (e- ) 9.1 x 10-28 -1.6 x 10-19 -1 Proton (p) 1.67 x 10-24 +1.6 x 10-19 +1 Neutron (n) 1.67 x 10-24 0 0 mass p = mass n = 1840 x mass e-
- 7. HISTORY OF THE ATOMHISTORY OF THE ATOM Joseph John Thompson found that atoms could sometimes eject a far smaller negative particle which he called an ELECTRONELECTRON
- 8. J.J. Thomson, measured mass/charge of e- (1906 Nobel Prize in Physics) A = alpha B = gamma C = beta
- 9. gold foil helium nuclei CHARGE OF AN ELECTRON Millikan oil drop experiment
- 10. HISTORY OF THE ATOMHISTORY OF THE ATOM Ernest Rutherford oversaw Geiger and Marsden carrying out his famous experiment. they fired Helium nuclei at a piece of gold foil which was only a few atoms thick. they found that although most of them passed through. About 1 in 10,000 hit
- 13. Plum Pudding model of an atom.Plum Pudding model of an atom.
- 14. Results of foil experiment if PlumResults of foil experiment if Plum Pudding model had been correct.Pudding model had been correct.
- 15. A nuclear atom viewed in crossA nuclear atom viewed in cross section.section.
- 16. atomic radius ~ 100 pm = 1 x 10-10 m nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m Rutherford’s Model of the Atom
- 17. Atomic StructureAtomic Structure AtomsAtoms are composed ofare composed of --protonsprotons – positively charged particles– positively charged particles --neutronsneutrons – neutral particles– neutral particles --electronselectrons – negatively charged particles– negatively charged particles Protons and neutrons are located in theProtons and neutrons are located in the nucleusnucleus.. Electrons are found in orbitals surrounding theElectrons are found in orbitals surrounding the nucleus.nucleus.
- 19. Atomic Structure Every different atom has a characteristic number of protons in the nucleus. atomic number = number of protons Atoms with the same atomic number have the same chemical properties and belong to the same element.
- 20. Atomic StructureAtomic Structure Each proton and neutron has a mass ofEach proton and neutron has a mass of approximately 1 dalton.approximately 1 dalton. The sum of protons and neutrons is the atom’sThe sum of protons and neutrons is the atom’s atomic massatomic mass.. IsotopesIsotopes – atoms of the same element that have– atoms of the same element that have different atomic mass numbers due todifferent atomic mass numbers due to different numbers of neutrons.different numbers of neutrons.
- 21. ATOMIC STRUCTUREATOMIC STRUCTURE the number of protons in an atom the number of protons and neutrons in an atom HeHe 22 44Atomic mass Atomic number number of electrons = number of protons
- 22. ATOMIC NUMBER (Z) = number of protons in nucleus MASS NUMBER (A) = number of protons + number of neutrons = atomic number (Z) + number of neutrons ISOTOPS are atoms of the same element (X) with different numbers of neutrons in the nucleus XA Z H 1 1 H (D) 2 1 H (T) 3 1 U235 92 U238 92 Mass Number Atomic Number Element Symbol
- 25. Two isotopes of sodium.
- 26. HISTORY OF THE ATOMHISTORY OF THE ATOM Niels Bohr studied under Rutherford at the Victoria University in Manchester. Bohr refined Rutherford's idea by adding that the electrons were in orbits. Rather like planets orbiting the sun. With each orbit only able to contain a set number of electrons.
- 29. ELECTRONS IN ORBIT ABOUTELECTRONS IN ORBIT ABOUT THE NUCLEUSTHE NUCLEUS
- 30. The Bohr Model of the AtomThe Bohr Model of the Atom
- 32. The Bohr Model of the Atom:The Bohr Model of the Atom: Ground and Excited StatesGround and Excited States • In the Bohr model of hydrogen, the lowest amountIn the Bohr model of hydrogen, the lowest amount of energy hydrogen’s one electron can haveof energy hydrogen’s one electron can have corresponds to being in thecorresponds to being in the nn = 1 orbit. We call this= 1 orbit. We call this itsits ground state.ground state. • When the atom gains energy, the electron leaps to aWhen the atom gains energy, the electron leaps to a higher energy orbit. We call this anhigher energy orbit. We call this an excited stateexcited state.. • The atom is less stable in an excited state and so itThe atom is less stable in an excited state and so it will release the extra energy to return to the groundwill release the extra energy to return to the ground state.state. • Either all at once or in several steps.Either all at once or in several steps.
- 35. Line Emission Spectrum of Hydrogen Atoms Every element has a unique emission spectrum
- 36. The Bohr Model of the Atom:The Bohr Model of the Atom: Hydrogen SpectrumHydrogen Spectrum • Every hydrogen atom has identical orbits, so everyEvery hydrogen atom has identical orbits, so every hydrogen atom can undergo the same energyhydrogen atom can undergo the same energy transitions.transitions. • However, since the distances between the orbits inHowever, since the distances between the orbits in an atom are not all the same, no two leaps in anan atom are not all the same, no two leaps in an atom will have the same energy.atom will have the same energy. – The closer the orbits are in energy, the lowerThe closer the orbits are in energy, the lower the energy of the photon emitted.the energy of the photon emitted. – Lower energy photon = longer wavelength.Lower energy photon = longer wavelength. • Therefore, we get an emission spectrum that has aTherefore, we get an emission spectrum that has a lot of lines that are unique to hydrogen.lot of lines that are unique to hydrogen.
- 37. The Bohr Model of the Atom:The Bohr Model of the Atom: Hydrogen SpectrumHydrogen Spectrum
- 38. Line spectrum of some elements
- 39. LIGHT EMISSION OF SODIUM ATOM Line spectrum