Atomic structure - AQA SynergyStructure of the atom
Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in shells. The numbers of subatomic particles in an atom can be calculated from its atomic number and mass number.
An atom has a central nucleusThe central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. The plural of nucleus is nuclei.. This is surrounded by electronSubatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. arranged in shells.
The nucleus is tiny compared to the atom as a whole:
the radius of an atom is about 0.1 nm (1 脳 10-10 m)
the radius of a nucleus (1 脳 10-14 m) is less than \(\frac{1}{10,000}\) of the radius of an atom
For comparison, the radius of a methane molecule is 0.5 nm (5 脳 10-10 m), the radius of a typical bacterium is 1 脳 10-6 m and the radius of a human hair is about 1 脳 10-4 m.
The nucleiNuclei is the plural of nucleus. The nucleus is the central part of an atom. It contains protons and neutrons, and has most of the mass of the atom. of all atoms contain subatomic particles called protonSubatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1.. The nuclei of most atoms also contain neutronUncharged subatomic particle, with a mass of 1 relative to a proton. The relative charge of a neutron is 0..
The masses of subatomic particles are very tiny. Instead of writing their actual masses in kilograms, we often use their relative massThe relative mass is the number of times heavier a particle is, compared to another.. The relative mass of a proton is 1, and a particle with a relative mass smaller than 1 has less mass.
Subatomic particle
Relative mass
Relative charge
Proton
1
+1
Neutron
1
0
Electron
Very small
-1
Subatomic particle
Proton
Relative mass
1
Relative charge
+1
Subatomic particle
Neutron
Relative mass
1
Relative charge
0
Subatomic particle
Electron
Relative mass
Very small
Relative charge
-1
The mass of an electron is very small compared to the mass of a proton or neutron. Since the nucleus contains protons and neutrons, most of the mass of an atom is concentrated in its nucleus.
Protons and electrons have equal and opposite electrical charges.