atomic structure

• element is a pure substance which cannot be broken down into anything simpler by chemical methods.
• graphite is a shiny non-metal.
• mercury, group I metals and non-metals have low melting and boiling point.
• Metals, graphite, diamond and semi-metals have high melting and boiling point.
• Mercury and bromine are liquid state at room temperature.
• Semi-metals only conduct electricity when they are heated or slightly impure.
• Boron and silicon are semi-metals.
• Isotopes are different atoms of an element which have the same number of protons but a different number of neutrons.
• Isotopes have same chemical properties because they have same number of electrons ( same electronic arrangements ).
• The relative atomic mass of an element is the weighted average relative isotopic mass of all the naturally occurring isotopes of that element on the 12C = 12.00 scale.