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substance that cannot be split up into simpler substances by chemical means
what did davy discover?
sodium, potassium, calcium, barium, strontium, magnesium
what is dobereiner associated with?
group of three elements with similiar chemical properties in which the atomic weight of the middle element is approx. equal to the average of the other two
what is newlands associated with?
groups of elements arranged in order of increasing atomic weight, in which the first and the eight element of each group have similair chemical properities
what is mendeleev's periodic law?
when elements are arranged in order of increasing atomic weight (ram), the properties of the elements vary periodically
how was mendeleev different to newlands?
- >he left gaps to make the elements fit into the proper column
- >in a few cases he had to reverse the order of elements in order to make them fall into groups of elements with similiar properties
define atomic number
number of protons in the nucleus of that atom
how ia the modern periodic table arranged?
in order of increasing atomic number
differences between modern periodic table and mendeleevs
- >modern.. increasing atomic number
- mend... increasing atomic weight (ram)
- >more elements in modern
- >no gaps in modern
- >modern.. transition elements listed in seperate block
define mass number
sum of the number of protons and neutrons in the nucleus of an atom of that element
who built the mass spectrometer
francis william aston
atoms of the same element with the same number of protons but different number of neutrons in the nucleus