Atoms, elements and compounds
each element is made from one type of atom
arranged in columns, called groups
atoms have a nucleus surrounded by electrons
when elements react, their atoms join with atoms of other elements. compounds are formed when two or more elements combine together
nucleus contains two types of particle, protons and neutrons
protons= positivie charge
neutrons= no charge
electrons = negative charge
electrons move around the nucleus
an atom has no overall charage because the number of protons is equal to the number of electrons and their charges are equal and opposite (proton +1 and electron -1)
all atoms of an element contain the same number of protons. this number is called the atomic number (or proton number) of the element.
elements are arranged in order of their atomic number in the periodic table.
the atomic number is also the number of electrons in an atom of the element
the mass number is the total number of particles in the nucleus of an atom, so it is the number of protons plus the number of neutrons
The arrangement of electrons…