Chemistry module 2

• Atom


  The smallest particle of an element. Atoms of different elements may also combine into systems called molecules, which are the smallest modules of chemical compounds.
• Atomic number


  The number of protons (also number of electrons) that the atom contains.
• Atomic mass or mass number


  The sum of an atom's protons and neutrons that are always expressed in whole numbers.
• Proton


  The positively charged particle in the nucleus of an atom.
• Neutron


  The particle with no charge in the nucleus of an atom.
• Electron


  The negatively charged particle that orbits the nucleus of an atom.

  
• The total number of protons in a given atom determines the atomic number of an element.
• The atomic mass or mass number is the sum of an atom's protons and neutrons that are always expressed in whole numbers.
• The number of protons equals the number of electrons in an electrically neutral atom.
• The difference between the mass number and atomic number equals the number of neutrons in the nucleus.
• Atomic notation


  • 12C - Carbon atom with 6 protons and 6 neutrons
  • 14N - Nitrogen atom with 7 protons and 7 neutrons

  
• The atomic number is always less than the atomic mass.
• Number of protons


  = Mass number
• The number of protons in an atom is equal to its mass number
• Sub-atomic particles


  • Proton
  • Electron
  • Neutron
• Electrons have almost no mass
• Nitrogen (N)


  • Number of protons: __
  • Number of electrons: __
  • Number of neutrons: __
• Potassium (K)


  • Number of protons: __
  • Number of electrons: __
  • Number of neutrons: __
• Neon (Ne)


  • Number of protons: __
  • Number of electrons: __
  • Number of neutrons: __
• Relative Atomic Mass (RAM)


  The mass of an atom compared to the mass of a hydrogen atom
• Hydrogen's atomic number is 1 and its mass number is also 1, meaning it has 1 proton, 1 electron, and no neutrons
• Isotopes


  Atoms of the same element with the same number of protons but different number of neutrons
• Carbon-14 is unstable because it has too many neutrons in its nucleus
• Relative Isotopic Mass


  The mass of an atom of the isotope relative to the mass of an atom of carbon-12
• Isotopes of Hydrogen


  • 1H
  • 2H
  • 3H

  
• Isotopes of Carbon


  • 12C
  • 13C
  • 14C
• Isotopes of Chlorine


  • 35Cl
  • 37Cl
• Mass Spectrometer


  An instrument that separates the individual isotopes in a sample of an element and determines the mass of each isotope and their relative abundance
• The relative atomic mass of chlorine is 35.5
• Electron Configuration


  The arrangement of electrons in an atom
• Electron Shells


  • 1st shell holds 2 electrons
  • 2nd shell holds 8 electrons
  • 3rd shell holds 18 electrons
  • 4th shell holds 32 electrons
• Electron Sublevels


  s, p, d, f
• The total number of electrons in an energy level can be found by the formula: number of electrons = 2n^2, where n is the number of the energy level
• Electron Configuration Examples


  • Hydrogen (H): 1s1
  • Lithium (Li): 1s2 2s1
  • Beryllium (Be): 1s2 2s2
  • Carbon (C): 1s2 2s2 2p2
  • Nitrogen (N): 1s2 2s2 2p3
  • Aluminum (Al): 1s2 2s2 2p6 3s2 3p1
  • Sulfur (S): 1s2 2s2 2p6 3s2 3p4
  • Potassium (K): 1s2 2s2 2p6 3s2 3p6 4s1
  • Bromine (Br): 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p5
• The periodic table organizes elements based on their atomic number and electron configuration
• Periodic Table Blocks


  • s-block
  • p-block
  • d-block
  • f-block
• The rows of the periodic table are called periods, and the columns are called groups
• Elements in the same group have the same number of electrons in their outer shell
• Elements in the same period have the same number of electron shells
• The elements in the same row have something in common