An element is a pure substance which cannot be made into any simpler substance by chemical means.
Columns are called periods and rows groups.
Protons have a .............. charge.
postive
negative
Electrons have a ............. charge.
positive
The atoms of an element contain a equal numbers of protons and electrons and so have no overall charge.
Every element has a unique atomic number. This is the number of electrons in the nucleus of each atom.
Mass number =
number of protons + number of neutrons
number of neutrons + number of electrons
number of electrons + number of protons
The number of neutrons can be calculated by subtracting
the mass number from atomic number
the atomic number from the mass number
Metals form ions. Non-Metals form ions.
In a chloride ion the atomic number gives us 17 protons. The negative charge means we have one more electron than protons so we have 18 electrons. The mass number minus the atomic number gives us 18 neutrons.
The seven diatomic
hydrogen
carbon
nitrogen
iodine
sodium
oxygen
chlorine
lithium
bromine
fluorine
The valency of sodium is 2.
The formula NaCl2 is correct for sodium chloride.
The formula Fe2(S04)2 is correct for iron(III)sulphate.
The formula for Sodium Sulphate is
NaSO3
NaSO4
Na2SO4
