Chemistry

• how did John Dalton think of the atom?

  As a solid sphere that could not be divided into smaller parts. His model did not include protons, neutrons, or electrons.
• The plum pudding model


  A cloud of positive charge, with negative electrons

  embedded in it. Protons and neutrons had not yet been

  discovered.

  
• what type of atom was discovered first?

  the electrons
• what led to the discovery of sub- atomic charged particles

  Scientists' experiments resulted in the discovery of sub‐atomic charged particles.
• sub-atomic charged particles are...


  the particles found inside an atom and are responsible for forming the structure of an atom.
• What is the alpha scattering experiment?


  Scientists fired small, positively charged alpha particles at a thin gold foil.
• What was the unexpected observation in the alpha scattering experiment?

  Some alpha particles bounced back and many were deflected, known as alpha scattering.
• What was the conclusion drawn from the alpha scattering experiment?

  Scientists proposed that the positive charge and mass of an atom are concentrated in a small space at its center, called the nucleus.
• nuclear model?


  When scientists replaced the plum pudding model with the nuclear model and suggested that the electrons orbit the nucleus.

  
• Do electrons in the nuclear model orbit at set distances?

  No, electrons in the nuclear model do not orbit at set distances.
• electron shell (bohr) model


  Niels Bohr calculated that electrons must orbit the nucleus at fixed distances. These orbits are called shells or energy levels.

  
• proton model


  Further experiments provided evidence that the nucleus contained smaller particles called protons.
• Who discovered the neutron?


  James Chadwick
• What is the charge of a neutron?

  No charge
• Where are protons and neutrons located?

  In the nucleus
• Where do electrons orbit in an atom?

  In shells around the nucleus
• What is the relative mass of protons and neutrons?

  they have the same mass so its 1
• How does the relative mass of electrons compare to protons and neutrons?

  It's so small we say it's almost 0
• How many electrons does it take to equal the mass of a single proton?

  Almost 2000 because their mass is so small
• size of atoms


  The atom has a radius of 1×10−10m. Nuclei are around 10,000 times smaller than atoms and have a radius of around 1×10−14m.
• What are elements?

  Substances made of one type of atom.
• What is unique about the atoms of an element?

  Each atom of an element will have the same number of protons.
• What are compounds made of?

  Different types of atoms chemically bonded together.
• Do atoms in a compound have the same number of protons?

  No, the atoms in a compound have different numbers of protons.
• What is a mixture?


  A mixture consists of two or more elements or compounds that are not chemically combined together.
• How can substances in a mixture be separated?


  The substances in a mixture can be separated using physical processes.
• Do processes for separating mixtures involve chemical reactions?

  No, these processes do not use chemical reactions.
• filtration separates:


  Insoluble solids from liquids

  
• crystallisation separates:


  soluble solid from a solution

  
• simple distillation separates:


  A solvent from a solution

  
• fractional distillation separates:


  2 liquids with similar boiling points

  
• paper chromatography:

  identifies substances from a mixture in a solution

  
• atomic number is


  the number of protons in the nucleus of an atom
• protons charge is


  +1, positive
• electrons charge is

  -1, negative charge
• neutrons charge is

  0, neutral
• equation for mass number

  protons + neutrons
• equation for atomic number


  number of protons
• relative mass of protons

  1
• relative mass of electrons

  0