Chemistry P1

• what is an atom?

  all substances are made of atoms. An atom is the smallest part of an element that can exist.
• how are atoms represented?

  atoms of each element are represented by a chemical symbol. e.g. O represents an atom of oxygen, NA represents an atom of sodium
• how many elements are there?

  there are about 100 elements. elements are shown in the periodic table
• how are compounds formed?

  compounds are formed from elements by chemical reactions.
• what do chemical reactions involve?

  the formation of one or more new substances, and often involve a detectable energy change. Compounds can only be separated into elements by chemical reactions
• what is a compound?

  two or more elements chemically bonded
• What is a mixture?

  two or more elements or compounds not chemically bonded. The chemical properties of each substance in the mixture are unchanged
• how can a mixture be seperated?

  Filtration, simple distillation, fractional distillation, chromatography, and crystallisation. these physical processes do not involve chemical reactions and no new substances are made.
• what were atoms originally described as?

  tiny spheres that couldnt be divided
• what did the discovery of the electron lead to?

  led to the plum pudding model. it suggested the atom is a ball of positive charge with negative electrons embedded in it
• what experiment lead to the nuclear model?

  alpha scattering experiment
• what conclusions did the alpha scattering experiment lead to?

  the mass is concentrated in the centre - particles reflected / deflected

  nucleus was charged - particles reflected / deflected

  a lot of empty space - particles went straight through
• how did Neil Bohr adapt the nuclear model?

  suggested electrons orbited nucleus at specific distances
• what did later experiments of the development of the atom lead to?

  led to the idea that the positive of any nucleus could be subdivided into a whole number of smaller particles, each particle having the same amount of positive charge. the name proton was given to these particles
• who provided evidence for the existence of the neutrons?

  James Chadwick
• what did James Chadwick provide?

  The discovery of the neutron within the nucleus. this was 20 years after the nucleus became an adapted scientific idea
• difference between plum pudding model and nuclear model?

  Plum pudding model: Atom is a positively charged sphere with negatively charged electrons embedded in it. Nuclear model: Atom has a small, dense, positively charged nucleus at the centre, with electrons orbiting around it. empty spaces between nucleus and electrons.
• what is the relative charge of particles in the atom?

  proton -> +1

  neutron -> 0

  electron -> -1
• how to calculate proton and electrons?

  number of electrons is equal to number of protons. this makes the overall charge of an atom neutral.

  its the atomic number
• what is the radius of an atom?

  1 x 10 ^ -10 m
• what is the radius of the nucleus?

  1 x 10 ^-14 m
• Where is the most of the mass of an atom?

  in the nucleus
• what is the relative mass of particles in an atom?

  proton - 1

  neutron - 1

  electron - very small
• what is the mass number?

  sum of protons and neutrons
• how to calculate neutrons?

  mass number - atomic number
• where can u find the mass number and atomic number?

  mass number is the top number

  atomic number is the bottom number
• what do the electrons in an atom occupy?

  the lowest available energy levels
• an example of an electronic structure?


  2, 8, 1
• What is the maximum number of electrons in the first shell ?

  2. It’s the lowest energy level
• what is the maximum number of electrons in the other shells?

  8
• How are the elements arranged in the periodic table?

  atomic number so elements with similar properties are in groups
• what do elements in the same group have?

  the same number of electrons in the outer shell and this gives them similar chemical properties
• what did they arrange the periodic table with before?

  they arranged them in order of atomic weight. the early periodic tables were incomplete and some elements were placed in inappropriate groups if the strict order of atomic weights were followed.
• what did Mendeleev overcome?

  mendeleev overcame some of the problems by leaving gaps for elements that he thought had not been discovered and in some places changed the order based on atomic weights. elements with properties predicted by Mendeleev were discovered and filled the gaps. knowledge of isotopes made it possible to explain why the order based on atomic weights was not always correct
• the three steps in developing the periodic table?

  Classification, organization, and prediction.
• how to find if an element is a metal or non metal?

  metals are on the left. non-metals on the right. elements that react to form positive ions are metals. elements that do not form positive ions are non-metals. majority of elements are metal
• what are the group 0 elements called and what are there properties?

  Group 0 elements are called noble gases. They have full outer electron shells and are therefore stable so dont easily form molecules. they all have 8 electrons on outer shell except helium which has 2. they are unreactive. The boiling point increase going down the group.
• What are the group 1 elements called and what are there properties?

  Alkali metals. They have one electron on the outer shell. The reactivity increases going down the group
• reaction of lithium with oxygen , water and chlorine?

  Oxygen: Lithium oxide (Li2O) Water: Lithium hydroxide (LiOH) and hydrogen gas (H2) Chlorine: Lithium chloride (LiCl)
• reaction on potassium with oxygen , chlorine and water?

  oxygen - potassium oxide

  chlorine - potassium chloride

  water - potassium hydroxide + hydrogen gas