Atoms and Isotopes

what is the basic structure of an atom

• positively charged nucleus - composed of protons and neutrons

• negatively charged shells surrounding nucleus - made up of electrons

what is the size of an atom?

radius = 1×10^-10 metres

what is the size of the nucleus compared to the atom

• radius = 1×10^-14 metres

• 1/10,000 of the radius of an atom

what is the relative charge and mass of subatomic particles?

particle	relative charge	relative mass
proton	+1	1
neutron	0	1
electron	-1	Negligible (1/1800)

what is the atomic number?

• the number of protons in an element.

• This is the same as the number of electrons in an element

• This is usually the bottom number on the periodic table

what is the mass number?

• the total number of protons and neutrons in an atom

• this is usually the top number on a periodic table

what is an isotope?

an element with the same number of protons, but a different number of neutrons