Rucete ✏ Chemistry In a Nutshell
The Atom Definition & Explanation
The smallest indivisible particle is considered an atom.
Atoms are neutral as they contain protons and electrons in equal numbers.
The majority of an atom is only empty space, as shown by Rutherford's Model.
Nearly all the mass of an atom is contained in the nucleus.
Proton
A particle in the nucleus of an atom with a positive charge. In an atom, the number of protons is equal to its atomic number.
Electron
A particle with negative charge and almost no mass. Electricity is a flow of electrons.
Neutron
A particle in the nucleus with approximately the same mass as a proton but it has no charge.
Atomic number (Z)
Both its position on the periodic table and the number of protons in the nucleus are given by the atomic number. In a neutral atom, the number of electrons outside the nucleus is also equal to the atomic number.
Mass number (A)
In the nucleus, the total number of protons and neutrons. The atom symbol of an element indicates the mass number at the top left and the atomic number at the top left.
The lower left corner of the component symbol.
(a) For an atom: Z = p = e
(b) For an ion: Z = p, and e = p – the charge on the ion
e.g. 23Na
p = e = 11
n = 23 – 11 = 12
Tags:
Chemistry in a nutshell