Week 1

• What is the charge of a proton?


  +1
• What is the charge of a neutron?


  0
• What is the charge of an electron?


  -1
• The mass of an atom is roughly the mass of what?

  The mass of the nucleus
• What is charge measured in?

  Coulombs
• What is the precise mass of an atom?


  Almost all nuclei weigh a little less than combined mass of protons & neutrons.

  (Small adjustments made to account for the binding energy that holds nucleus together)
• What are isotopes?


  Atoms of same element with same number of protons but different number of neutrons ( so different weights).
• What is a mass spectrometer?


  Instrument used to observe distribution of isotopes in atoms & molecules
• Why do some isotopes undergo nuclear decay?


  They have an unstable nucleus, so want to become more stable.
• What is alpha decay?


  Nucleus of some heavy atoms eject a particle containing 2 protons & 2 neutrons ( helium).
• What is beta decay?


  A neutron in an atom can split into a proton & an electron.

  Proton stays in nucleus but electron leaves. Emitted electron is a beta particle.
• What is neutron capture?


  Nucleus absorbs & emits particles simultaneously.
• What is nuclear fission?


  Nuclei can react by absorbing neutrons & splitting into 2 smaller nuclei.
• What is nuclear fusion?


  In extreme conditions, nuclei of small atoms can combine to produce a larger nucleus.
• Relative atomic mass:


  Average mass of an atom of an element on a scale where an atom of carbon-12 is exactly 12.
• What happened 1 second after the big bang?


  protons, neutrons & electrons created
• What happened a few minutes after the Big Bang?


  Protons & neutrons combine to form helium & lithium nuclei
• 300,000 years after Big Bang:


  electrons & nuclei combine to form hydrogen (75%), helium (25%) & some lithium atoms
• 1 billion years after Big Bang:


  Atoms aggregate to form stars

  In star, energy released by hydrogen atoms fusing together to form helium

  When H used up, He fuse together (in 3s) to create carbon
• How long do large stars last?


  Few million years (rapidly burn fuel)
• What are supernovae?


  Large stars finish burning hydrogen & collapse under force of gravity releasing huge amounts of energy in cosmic explosion.

  Forces involved are sufficient to fuse atoms to form medium-sized atoms e.g, iron.
• Where does a neutron star form?


  At crab nebula centre.

  When neutron stars collide, large atoms are ejected e.g, gold
• What are light elements?


  Few elements produced by high energy collisions that can take place anywhere & result in protons & neutrons being ejected from nucleus of heavier atom.
• 1 mole is...


  6.022 x 10(23) atoms/molecules
• 1 Da is...


  1g mol-1