an element with the same atomic no. as another element but different mass no.
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what is the relative charge and relative mass of a electron?
relative charge = -1 relative mass = 0
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what is the relative charge and relative mass of a proton?
relative charge = +1 relative mass = 1
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what is the relative charge and relative mass of a neutron?
relative charge = 0 relative mass = 1
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how is the group no. indicated?
the group no. is indicated by the number of electrons in its last shell
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how is period number indicated?
the period no. is indicated by the number of shells surrounding the nucleus
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What was the significance of Mendeleev leaving gaps in his periodic table?
The elements had not yet been discovered
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Why did Mendeleev swap the order of some of the elements in his periodic table?
Atomic weights are less important than atomic number. Mendeleev recognised that the pattern in elements' properties was very important, so he swapped some elements round, ignoring their atomic weights.
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what did the English scientist called John Newlands do in the formation of the periodic table
in 1864 he arranged all the elements known at the time into a table in order of relative atomic mass.
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put the following scientist into order according to the development of the period table ; John Newlands ,Dmitri Mendeleev, Johann Döbereiner
Johann Döbereiner, John Newlands, Dmitri Mendeleev
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what did Döbereiner put forward into the development of the periodic table?
In 1817 Johann Döbereiner proposed his 'law of triads'. Each of Dobereiner's triads was a group of three elements. The appearance and reactions of the elements in a triad were similar to each other.
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what is ionic bonding between?
non metals and metals
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what is an ion?
a charged atom
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what is inter-molecular force
force between molecules
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how is a giant ionic lattice formed
Ionic bonds are the electrostatic forces of attraction between oppositely-charged ions ; they bond to create giant ionic lattice
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why is the melting point of sodium chloride is lower than that of magnesium oxide
because it has weaker ionic bonds as the Na+ and Cl– ions in sodium chloride have less charges than the Mg2+ and O2– ions in magnesium oxide and Na+ ions are larger than Mg2+ and can't get as close to the negatively charged ions
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construct the general word and numerical formula of alkali metals reacting with water
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