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. The ion has two positive protons but one electron so it ...

For example, according to classical physics, the electrons orbiting the nucleus should lose energy until they spiral down into the center, collapsing the atom. Bohr proposed adding to the model ...

For example, according to classical physics, the electrons orbiting the nucleus should lose energy until they spiral down into the center, collapsing the atom. Bohr proposed adding to the model ...

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 ...

SCIENCE is steadily becoming severely specialised. The proportion of amateurs (in the restricted sense of the word) among original workers of all ranks decreases slowly but surely. The average ...