chemistry

• is the nucleus postive or negatively charged?

  positive
• the top number of an element is what?

  the mass number
• what does the mass number represent?

  protons and neutrons
• the bottom number of an element is what?

  the atomic number
• the atomic number represents what?

  protons
• balance this equation:_N2 + _F2 --> _NF3?


  N2+ 3 F2 --> 2 NF2
• what are properties of group 1 metals?

  -very reactive

  -low density

  -soft
• group 1 metals reactivity increases as you go down the group
• group 7 properties?

  -poor conductors

  -low melting+ boiling points
• as you go down group 7, their reactivity decreases
• jhon dalton made what model of the atom?


  solid sphere model/ bowling ball model
• JJ Thomson created what odel of the atom?

  the plum pudding model
• Neihls bohr's model was then accepted
• the group number in the periodic table tells you what?

  how many electrons there are in the outer shell
• the periodic number tells you what?


  how may shells there are
• mendeleev ordered the periodic table in order of their atomic weight and left gaps for new elements. he predicted what those elements would be