Atom

• Democritus was among the first to suggest the existence of atoms, believing they were indivisible and indestructible

  
• Democritus's ideas about atoms were not based on the scientific method but on philosophy
• John Dalton's atomic theory includes:

  • All elements are composed of tiny indivisible particles called atoms
  • Atoms of the same element are identical, and atoms of any one element are different from those of any other element
  • Atoms of different elements combine in simple whole-number ratios to form chemical compounds
  • In chemical reactions, atoms are combined, separated, or rearranged, but never changed into atoms of another element
• Elements can be subdivided into smaller particles called atoms, which still retain the properties of the element

  
• Individual atoms are observable with instruments like scanning tunneling microscopes
• Atoms are divisible into subatomic particles, including electrons, protons, and neutrons
• J.J. Thomson discovered the electron in 1897 using a cathode ray tube
• Robert Millikan determined the mass of the electron to be 1/1840 the mass of a hydrogen atom, with one unit of negative charge
• Eugen Goldstein observed the proton in 1886, a particle with a positive charge and a relative mass of 1
• James Chadwick confirmed the existence of the neutron in 1932, a particle with no charge but a mass nearly equal to a proton
• Subatomic particles include electrons (e-), protons (p+), and neutrons (no)
• Thomson's atomic model was the "plum pudding" model, where electrons were like plums embedded in a positively charged "pudding"
• Ernest Rutherford's Gold Foil Experiment in 1911 showed that the atom is mostly empty space, with a dense, positively charged nucleus
• Rutherford's experimental evidence led to the nuclear model of the atom, where the nucleus is composed of protons and neutrons, and electrons occupy most of the volume
• Attachment is a strong reciprocal emotional bond between an infant and a primary caregiver

  
• Schaffer and Emerson's 1964 study on attachment:

  • Aim: identify stages of attachment / find a pattern in the development of an attachment between infants and parents
  • Participants: 60 babies from Glasgow
  • Procedure: analysed interactions between infants and carers
  • Findings: babies of parents/carers with 'sensitive responsiveness' were more likely to have formed an attachment
• Freud's superego represents internalized societal values and standards
• Atoms are composed of identical protons, neutrons, and electrons

  
• Elements are different because they contain different numbers of protons
• The 'atomic number' of an element is the number of protons in the nucleus
• Mass number is the number of protons and neutrons in the nucleus of an isotope
• Complete symbols of elements contain the symbol of the element, the mass number, and the atomic number
• Isotopes are atoms of the same element having different masses due to varying numbers of neutrons
• Isotopes are named by putting the mass number after the name of the element
• Atomic mass is the average of all the naturally occurring isotopes of an element