chemistry definitions

• what is Daltons atomic theory?

  all matter is made up over very small particles called atoms and all atoms are indivisable
• cathode rays are?

  streams of negatively charged particles called electrons
• what is a energy level?


  fixed energy value that an electron in a atom may have
• ground state


  the electron occupies the lowest available energy level
• excited state


  electron occupies a higher energy level than ground state
• Heisenberg's uncertainty principal

  it is impossible to find velocity and position of an electron at the same time
• orbital?

  region in space where there is a high probability of finding an electron
• sublevel?

  subdivision of main energy levels and consists of one or more orbitals of same energy
• element?

  a substance that cannot be broken down in to simpler substances by chemical means
• triad?

  group of three elements with similar chemical properties atomic weight of middle element is equal to average of other two
• newlands octaves?

  arrangement of elements where first and eight element have similar properties
• Mendeleev's periodic table?

  elements arranged in increasing atomic weight properties recur periodically
• modern periodic table?

  increasing atomic number
• modern periodic law?

  when elements are arranged in order of increasing atomic number the properties of the elements recur periodically
• atomic number?

  number of protons in the nucleus of an atom
• mass number?

  number of protons and neutrons in the nucleus of and atom
• isotopes?

  atoms of the same elements with different mass numbers due to different numbers of neutrons in the nucleus
• relative atomic mass?

  average of the isotopes of an element as they occur naturally taking their abundance into account expressed on a scale in which the atoms of the carbon 12 isotope have a mass of 12 untis
• principal of mass spectrometry?

  charged particles moving in a magnetic field are deflected to different extents according to their masses and thus separated according to these masses
• electron configuration?

  arrangement of electrons in an atom of an element
• Aufbau principle?

  when building up the electron configuration of an atom in its ground state electron occupies the lowest available energy level
• hunds rule of maximum multiplicity?

  when two or more orbitals of equal energy are available the electron occupies then single before in pairs
• pauli exclusion principal?

  no more than two electrons may occupy an orbital and must have opposite spins
• compound?

  a substance made up of two or more different elements chemically combined
• octet rule?


  Atoms tend to gain, lose, or share electrons in order to achieve a full outer shell of eight electrons, known as the octet rule.
• ion?

  charged atom or group of atoms
• ionic bond?

  force of attraction between oppositely charged ions in a compound
• transition metal?


  forms at least one ion with a partially filled d sublevel
• molecule?

  A group of atoms bonded together.
• valency?

  number of atoms of hydrogen or any monovalent element in which each atom of an element combines
• sigma bond?

  head on overlap of two orbitals
• pi bond?

  sideway overlap of p orbital
• electronegativity?

  relative attraction than an atom has for the spared pair of electrons in a covalent bond
• polar covalent bonds?

  unequal sharing of the pairs of electrons one is slightly positive one is slightly negative
• intramolecular bonding?

  takes place within a molecule covalent bonding
• intramolecular forces?

  forces of attraction that exist between molecules van der waals forces
• van der waals forces?

  weak attractive forces between molecules resulting from the formation of temporary dipoles only forces between non polar molecules
• dipole dipole forces?

  forces of attraction between the negative pole of one polar molecule and the positive pole of another
• hydrogen bonds?

  types of dipole dipole attraction between molecules in which hydrogen atoms are bonded to nitrogen oxygen or fluorine. carries a partial positive charge
• law of conservation of mass?

  total mass of a product of a chemical reaction is the same as the total mass of the reactants