trends and the history of the atom Flashcards
what is the atomic radius trend
the measure of the size of atoms, usually from the nucleus to the other shell
what is the electronegativity trend
The ability for the atom to attract or hold onto its electrons in a chemical bond. the closer it is to fluorine the higher the electronegativity.
what is the ionisation energy trend
the energy required to remove one mole of the electron from 1 mole of atoms
what is the atomic radius trend down a group
due to the atom gaining a valence shell, the radius becomes larger due to the gain of shell
what is the atomic radius across a group
due to the electrostatic attraction between the electrons and the positive nucleus being stronger. the valence electron gets pulled in closer to the nucleus causing the atomic radius to decrease
what is the electronegativity down a group
decreases down a group since the valence electrons are further from the nucleus
what is the electronegativity across a period
due to the electrostatic attraction being stronger between the nucleus and valence electrons, the electrons become closer to the nucleus causing the electronegativity to increase due to the electrons being more tightly attracted to an atom
what is the ionisation down a group
due to the valence shells being further away, the electrostatic attraction isn’t as strong between the nucleus and the electrons. this causes the amount of energy to remove an electron decrease
what is the ionisation across a group
due to the valence shells being closer to the nucleus due to the strong electrostatic attraction. the amount of energy needed to lose an electron is increased
what are the two main categories of matter
pure substances and mixtures
what are homogeneous mixtures
a mixture which has a uniform composition and properties throughout
what are heterogeneous mixtures
a mixture that doesn’t have uniform composition and properties throughout
which five scientists were involved in developing the structure of the atom
John Dalton, JJ Thompson, Ernest Rutherford, Bohr, Chadwick
what involvement did john dalton have with the structure of the atom
used carbon as an example and stated that all atoms in carbon are the same but are different form that of sulphur
what involvement did JJ Thompson have with the structure of the atom
based on his experiments came up with the ‘plum pudding model’ where the atom was a sphere of positive charge and negative electrons were dispersed inside it.
what involvement did Ernest rutherford have with the structure of the atom
through his gold foil experiment, he designed a model with the small but dense positive centre with electrons surrounding and lots of empty space
what involvement did Bohr have with the structure of the atom
electrons have energy levels
what involvement did Chadwick have with the structure of the atom
he discovered the neutrons in the atom
how are al atoms held together
an electrostatic attraction between the nucleus and the electrons
what are isotopes
atoms of an element with the same number of protons but different numbers of neutrons and are represented in the form A X (IUPAC) or X-A. they have the same electron configuration and similar chemical properties but have different physical properties
what is the relative mass of an atom
the ratio of the average mass of the atom to 1/12 the mass of an atom of 12C; relative atomic masses of the elements are calculated from their isotopic composition
what are allotropes
a different form of the same element. for example, diamond and graphite are allotropes of carbon. these all have different chemical properties
what are fullerenes
a newly formed allotrope of carbon that was found by harold Kroto. the molecule known as buckminsterfullerene was the first C60 fullerene to be discovered in 1985. it consists of 60 carbon atoms covalently bonded into a cage structure consisting of 12 pentagons and 20 hexagons, resembling a soccer shape
what is electron affinity
when an electron is added to an atom to give a negative ion
