Atoms, isotopes and ions

• Atoms are made up of protons, neutrons and electrons.
• Change the number of neutrons in an atom and it becomes an isotope, change the number of electrons, it becomes an ion.
• The structure of the atom includes protons, neutrons and electrons.
• Atoms are very small, they have a radius of around 1 × 10 -10 metres.
• The modern view of the atom close atom The smallest part of an element that can exist is of a nucleus close nucleus The central part of an atom.
• The nucleus contains protons and neutrons, and has most of the mass of the atom.
• The plural of nucleus is nuclei.
• A proton is a subatomic particle with a positive charge and a relative mass of 1.
• The relative charge of a proton is +1.
• A neutron is an uncharged subatomic particle, with a mass of 1 relative to a proton.
• The relative charge of a neutron is 0.
• An electron is a subatomic particle, with a negative charge and a negligible mass relative to protons and neutrons, orbiting outside the nucleus.
• Each particle in the atom has its own charge and its own mass.
• Protons and neutrons are the heaviest particles in an atom and as a result they make up most of the mass close mass The amount of matter an object contains.
• Mass is measured in kilograms (kg) or grams (g) of the atom.
• The mass of electrons is often not considered to be significant.
• The number of protons is what defines the element.
• An atom with six protons in its nucleus will always be carbon, and uranium will always have 92 protons.
• The total number of protons and neutrons is called the mass number.
• The atomic number is also called the proton number and the number of protons is called the atomic number.
• In a neutral atom, the number of electrons is always the same as the number of protons.
• If the atom becomes ionised, the number of electrons will change.
• An ion is an atom that has lost or gained one or more electron.
• Mass number and atomic number are two important pieces of information about an atom.
• An atom can be represented using the symbol notation: \(_{Z}^{A}\textrm{X}\) Where: A is the mass number Z is the atomic number X is the symbol.
• Chlorine (Cl) can be shown as: This symbol shows that chlorine has 35 particles in the nucleus (protons and neutrons), 17 of which are protons.
• Chlorine also has 18 neutrons (35 - 17) and, as the number of electrons and protons are equal in a neutral atom, chlorine also has 17 electrons.