atomic structure

• All matter is composed of atoms, which are the smallest parts of an element that can take place in chemical reactions.
• Atoms are mostly made up of empty space around a very small, dense nucleus that contains protons and neutrons.
• The nucleus has an overall positive charge.
• The protons have a positive charge and the neutrons have a neutral charge.
• Negatively charged electrons are found in orbitals in the empty space around the nucleus.
• The basic structure of an atom is composed of a nucleus containing protons and neutrons, and electrons in orbitals in the empty space around the nucleus.
• The protons, neutrons and electrons that an atom is made up of are called subatomic particles.
• The mass and charge of subatomic particles are compared to each other, and so are called 'relative atomic masses' and 'relative atomic charges'.
• Protons and neutrons have a very similar mass, so each is assigned a relative mass of 1.
• Electrons are 1836 times smaller than a proton and neutron, and so their mass is often described as being negligible.
• The charge of a single electron is -1.602 x 10 coulombs, whereas the charge of a proton is +1.602 x 10 coulombs.
• The atomic number, or proton number, is the number of protons in the nucleus of an atom and has the symbol Z.
• The atomic number is also equal to the number of electrons present in a neutral atom of an element.
• The elements can be divided into four blocks according to their outer shell electron configuration.
• Chromium and copper have different electron configurations than expected, as the [Ar] 3d4s and [Ar] 3d4s configurations are energetically stable.
• The transition metals fill the 4s subshell before the 3d subshell but lose electrons from the 4s first and not from the 3d subshell, as the 4s subshell is lower in energy.
• Free radicals are formed when a molecule undergoes homolytic fusion where the two electrons of a covalent bond are split evenly between the two atoms.
• The full electron configuration describes the arrangement of all electrons from the 1s subshell up.
• Chlorine radical has the electron configuration 1s2s2p3s3p, with two of the three p orbitals having paired electrons and one having an unpaired electron.
• Ions are formed when atoms lose or gain electrons, with negative ions being formed by adding electrons to the outer subshell and positive ions being formed by removing electrons from the outer subshell.
• A free radical is a species with one or more unpaired electron, represented by a dot.
• Writing out the electronic configuration tells us how the electrons in an atom or ion are arranged in their shells, subshells and orbitals, which can be done using the full electron configuration or the shorthand version.
• The shorthand electron configuration includes using the symbol of the nearest preceding noble gas to account for however many electrons are in that noble gas.
• Electrons occupy the lowest energy levels first before filling those with higher energy.
• This proves that the proton is positively charged.
• A beam of protons is deflected away from the positive plate and towards the negative plate.
• When a beam of electrons is red past the electrically charged plates, the electrons are deflected very easily away from the negative plate towards the positive plate.
• The mass of the electron is negligible.
• The particle is neutral in character; it is not attracted to, or repelled by, the negative or positive plate.
• Protons are deferred less than electrons, this also shows that protons are heavier than electrons.
• A beam of neutrons is not deflected at all.
• The lighter electrons undergo much more deception than the protons.
• Protons, neutrons and electrons behave differently when they move at the same velocity in an electric field.
• The mass of an atom is concentrated in the nucleus, because the nucleus contains the heaviest subatomic particles (the neutrons and protons).
• The electrostatic attraction between the positive nucleus and negatively charged electrons orbiting around it is what holds an atom together.
• Electrons have a very small mass, as they are easily deflected.
• Electrons orbit the nucleus of the atom, contributing very little to its overall mass, but creating a 'cloud' of negative charge.
• The nucleus is also positively charged due to the protons.
• This proves that the electrons are negatively charged; like charges repel each other.
• The mass of the atom is concentrated in the positively charged nucleus which is attracted to the negatively charged electrons orbiting around it.