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C2.04 The structure of the atom - Coggle Diagram
C2.04 The structure of the atom
Atomic structure
Rutherford showed that
An atom is mostly space occupied by the negatively charged electrons, surrounding a very small, positively charged nucleus
The nucleus is at the centre of the atom and contains almost all the mass of the atom
Measuring the size of atoms
The mass of one atom can be compared to the mass of a carbon atom using a mass spectrometer
The element carbon is chosen as the standard
Sub-atomic particles
Protons and neutrons have almost the same mass. It is 1,67.10^-24g
Electrons have no mass at all. It is 9,11.10^-28g
Protons and electrons have equal and opposite charges
Neutrons are electrically neutral or have no charge
A single atom is electrically neutral or it has no overall electric charge
Proton (atomic) number and nucleon number
Proton number or atomic number shows the number of protons in the nucleus of an atom
Nucleon number fo mass number shows the total number of protons and neutrons present
Isotopes
Atoms of the same element which have the same proton number but a different nucleon number or neutron number
Isotopes of an element have the same chemical properties because they have the same electron structure
The number of electrons in an atom that decides the way in which it forms bonds and reacts with other atoms
Some physical properties of the isotopes are different because the masses of the atoms differ and therefore other properties, such as density and rate of diffusion, also vary
Some isotopes have unstable nuclei, they are radioisotopes and emit various forms of radiation
The atoms have the same number of protons and electrons but different nubers of neutrons in their nuclei
Radioisotopes
The imbalance of neutrons and protons in their nuclei causes them to be unstable so the nuclei break up spontaneousy, emitting certain types of radiation
Relative atomic masses
The average mass of naturally occurring atoms of an element on a scale where the carbon-12 atom has a mass of exactly 12 units
1 atomic mass unit (a.m.u) = 1/12 X mass of one atom of carbon-12