Chemistry key concepts

• How did mendeleev arrange the elements into the periodic table ?

  •He arranged them in order of relative atomic mass

  • He checked the properties of the elements and their compounds

  •He swapped some so similar properties of that elements lined up

  •He left gaps where he thought other elements were and predicted their properties

  • His predictions fitted well when the elements were discovered
• What were daltons original ideas about atoms ?

  •Atoms can’t be broken down

  •During chemical reactions atoms rearrange to make different substances
• What was discovered about the atom after subatomic particles were discovered ?

  •Protons, neutrons and electrons can be broken down

  • Atoms of an element have the same electrons and protons but different neutrons

  • Different elements have different protons and electrons
• Why is it not true that the elements were arranged in order of increasing relative atomic mass ?

  As Mendeleev thought he arranged it in increasing relative atomic mass, but this wasn’t true due to the relative abundance of isotopes of some pairs
• How does the existence of isotopes results in relative atomic masses of some elements not being whole numbers ?


  •As an Element could contain two different isotopes

  • Mass numbers are a whole number as it’s not possible to have part of a neutron or proton
• What’s the mass number ?

  Number of protons and neutrons in an atom.
• What’s the atomic number?

  The number of protons in an atom's nucleus.
• How is the periodic table arranged?

  • The elements are arranged in order of increasing atomic number in rows called periods

  • Elements with similar properties are placed in the same vertical columns called groups
• How are ionic bonds formed ?

  Ions form when a metal reacts with a non- metal by transferring electrons

  • Positive ions = cations

  • Negative ions = anions
• What’s a dot and cross diagram?

  
• What are the properties of metals ?

  Metals are shiny Solids, with high melting points, high density and are good conductors of electricity
• Properties of non-metals ?

  Non-metals have low boiling points and are poor conductors of electricity.
• why do atoms contain equal numbers of protons and electrons ?

  Atoms contain equal numbers of protons and electrons, so they have equal numbers of positive and negative charges and so are neutral overall
• What are isotopes?

  Isotopes are atoms of the same element that have different numbers of neutrons but the same number of protons
• Where are metals found on The periodic table ?

  Metals are mainly found on the left hand side and the middle of the periodic table
• Where are non-metals mainly found on the periodic table ?

  Mainly found on the right hand side
• Why is the periodic table divided by metals and non-metals ?

  The division is caused bu the difference in properties,

  • metals lose electrons

  • non-metals gain electrons
• What’s the relative charges of the subatomic particles ?

  • proton = +1

  • neutron = 0

  • electron = -1
• What are the relative masses of the subatomic particles ?

  • proton = 1

  • neutron = 1

  • electron = 1/1836 or 0.0005
• Describe the structure of an atom ?

  Nucleus, protons, neutrons, electrons.

  
• Describe the nucleus compared to the atom?

  The nucleus is very small compared to the overall size of the atom
• where is most of the mass of an atom concentrated?

  Most of the mass is concentrated at the nucleus
• Explain the formation of ions

  • metal atoms lose electrons to form positively charged ions

  • non-metals atoms gain electrons to form negatively charged ions
• Describe how the dalton model has changed over time (due to the discovery of subatomic particles) ?

  • 1803- Daltons original ideas
  • 1897- Thomson discovered electrons
  • 1909-11- Rutherford discovers nucleus and electrons
  • 1913- Bohr discovers that electrons occupy shells
  • 1918- Rutherford discovers protons
  • 1932- Chadwick discovers neutrons
• How are the electronic configurations of an element related to its position in the periodic table ?

  • number of circles = proton number

  • number of electrons in outer shell = group number

  • total number of electrons in all shells = atomic number

  
• What happens to the formation of ions in group 1,2,6 and 7 ?

  Group 1: Form +1 ions Group 2: Form +2 ions Group 6: Form -2 ions Group 7: Form -1 ions
• What’s an element

  A substance made from atoms with the same number of protons in the nucleus
• What’s an atom

  the smallest particle of an element that still has its chemical properties
• What’s a molecule ?

  It consists of two or more atoms chemically joined together
• What’s a compound ?

  Two or more different elements chemically joined together
• What’s an ion ?

  A charged particle formed when an atom gains or loses electrons
• What ion does metal atoms form ?

  positive ions by losing electrons
• What ion does non metals form ?

  Negative ions by gaining electrons
• What’s the purpose of chemical equations ?

  They show what happens in chemical reactions
• What’s a reactant ?

  The substances that undergo a chemical change in a reaction
• What’s a product ?

  The new substances formed from the reaction
• What’s state symbol is a solid ?

  ( s )
• What state symbol is a gas ?

  ( g )
• What state symbol is a liquid ?

  ( l )
• What’s state symbol’ is aqueous solution ?

  ( aq )