Atomic Structure. From Molecules to Quarks

Transcription

1 Atomic Structure From Molecules to Quarks

2

3 ELECTRONS Negatively charged particles that circle the nucleus.

4 Bohr s Atom electrons in orbits nucleus

5 Inside the Atom The Nucleus Contains Protons & Neutrons Protons Positively charged particles Neutrons No Charge

6 ATOMIC STRUCTURE Particle Charge Mass proton + 1 charge 1amu neutron 0 1amu electron -1 charge 1/1836 Amu = atomic mass unit 1 amu = 1.66 x 10-24g

7 Relative Sizes Thus 99.99% of the mass of an atom comes from the nucleus (protons and neutrons) and essentially nothing from electrons The major volume of atoms coming from the electron cloud. Remember that most of the atom is empty space.

8 Periodic Table & Atomic Number Atomic Number The number of PROTONS in the nucleus of the atom The atomic number identifies the element Atoms are electrically neutral # of PROTONS = # of ELECTRONS Mass Number The total number of PROTONS and NEUTRONS in the nucleus of an atom.

9 Isotopes Isotopes atoms of the same element that differ in the number of neutrons in the nucleus Because isotopes of an element have different numbers of neutrons, they have different mass numbers.

10 Hydrogen - Lithium

11 Carbon

12 Periodic Table

13 Quarks Quarks are the fundamental building blocks of nature. They combine to form larger particles, such as protons and neutrons.

14 Quarks The first family consists of Up and Down quarks, the quarks that join together to form protons and neutrons. The second family consists of Strange and Charm quarks and only exist at high energies. The third family consists of Top and Bottom quarks and only exist at very high energies. Generations Charge = -1/3 Charge = +2/3 I II III d s b (down) (strange) (bottom) u c t (charm) (top) (up)

15 Quarks Add the Charges = (+2/3) + (+2/3) + (-1/3) = 1 net charge 1 up 1 up 1 Down = (+2/3) + (-1/3) + (-1/3) = 0 net charge 1 up 1 Down 1 Down

16 Just FOUR particles make up all of the visible matter in the Universe* electron neutrino up quark down quark

17 But, the Universe does have other particles up its sleeve. For one thing, each of the matter particles has a twin. No, not an evil twin electron neutrino up quark down quark

18 an ANTIMATTER twin. electron neutrino up quark down quark positron anti-neutrino anti-up quark anti-down quark

19 Antimatter is not the stuff of science fiction. It exists. It is the stuff (or rather, the anti-stuff) of science fact. electron neutrino up quark down quark positron anti-neutrino anti-up quark anti-down quark

20 Matter, Antimatter: What s the difference? There is one essential and obvious difference: A particle of matter that has an ELECTRIC CHARGE has an antiparticle twin with the exact opposite charge.

21 Matter, Antimatter: What s the difference? There is one essential and obvious difference: A particle of matter that has an ELECTRIC CHARGE has an antiparticle twin with the exact opposite charge. For example, if the electron has a charge of 1, then its antiparticle, the positron, has a charge of +1. Electron Charge: 1 1 Positron Charge: +1 +1

22 PROTON (p) +⅔ Composed of: 2 up quarks and 1 down quark ⅓ +⅔ ANTIPROTON (p): ⅔ ⅔ +⅓ Total charge: ⅔ + ⅔ ⅓ = +1 Composed of: 2 anti-up quarks and 1 anti-down quark Total charge: -⅔ ⅔ + ⅓ = 1

23 NEUTRON (n) ⅓ Composed of: 1 up quark and 2 down quarks ⅓ +⅔ ANTINEUTRON (n): +⅓ ⅔ +⅓ Total charge: ⅔ ⅓ ⅓ = 0 Composed of: 1 anti-up quark and 2 anti-down quarks Total charge: -⅔ + ⅓ + ⅓ = 0 Notice that the antineutron also has zero charge. If a particle has no charge, then its antiparticle has no charge.

24 Let us picture a hydrogen atom as an electron orbiting its nucleus, a proton. BUT REMEMBER this is NOT an accurate depiction! (For one thing, in the proper scale, our electron would have to be drawn about 1 kilometer away from the proton). Hydrogen (H) Let us now picture an antihydrogen atom as a positron orbiting its nucleus, an antiproton. (The same warnings apply!) AntiHydrogen (H) -

25 THEORETICALLY SPEAKING, COMBINATIONS OF POSITRONS, ANTIPROTONS AND ANTINEUTRONS COULD GENERATE ANTI-VERSIONS OF ALL OF THE ELEMENTS IN THE PERIODIC TABLE.

26 The Muon A muon is a negatively charged particle, similar to an electron, but about 200 times heavier. Muons fall into the class of particles known as leptons. A heavy Electron

27 The Neutrino The neutrino and its friends are similar to the more familiar electron, with one crucial difference: neutrinos do not carry electric charge. Because neutrinos are electrically neutral, they are not affected by the electromagnetic forces which act on electrons. Neutrinos are affected only by a "weak" subatomic force of much shorter range than electromagnetism, and are therefore able to pass through great distances in matter without being affected by it. If neutrinos have mass, they also interact gravitationally with other massive particles, but gravity is by far the weakest of the four known forces.

28 It is known that the 100s of particles are all made from how many fundamental particles? 6 quarks, 6 leptons, 6 antiquarks, 6 antileptons, and the force carriers.