Ions
Normally, atoms are neutral. They have the same number of Subatomic particle with a positive charge and a relative mass of 1. The relative charge of a proton is +1. in the The 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. as they have Subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons. orbiting around the nucleus.
Atoms can lose or gain electrons due to collisions or other interactions. When they do, they form charged particles called Electrically charged particle, formed when an atom or molecule gains or loses electrons.:
- if the atom loses one or more electrons, it becomes a positively-charged ion
- if the atom gains one or more electrons, it becomes a negatively-charged ion
A helium atom has two electrons in an energy level outside the nucleus. The atom is neutral as it has two positive protons and two negative electrons.
A helium atom that has lost or gained an electron is an ion.
If the ion has two positive protons but one negative electron, it is a positive ion.
If the ion has two positive protons but three negative electrons, it is a negative ion.
The Bohr atom
Even though Rutherford had proven the existence of the The 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., scientists were unsure how electrons fitted into this new model.
In 1913, Niels Bohr revised Rutherford’s model by suggesting that the electrons orbited the nucleus in different energy levels or at specific distances from the nucleus.
By doing this, he was able to explain that since particular chemicals burn with certain-coloured flames; the pattern of energy released by electrons in the chemical reaction must be the same for every single atom of that element.
Therefore, electrons cannot be arranged at random, but they must have fixed levels of energy within each type of atom.
Bohr’s ‘solar system’ model of the atom is the way that most people think about atoms today.
When atoms absorb energy, perhaps by absorbing electromagnetic radiation, the electrons at a particular level are pushed up to higher levels (at bigger distances from the nucleus) - they become ‘excited’. In time, they jump back down to a lower level releasing light of definite frequencies.