Trends in the periodic table Flashcards
what are the trends in the periodic table
valence electrons, number of electron shells, atomic radius, electronegativity, first ionisation energy and metallic properties
what is effective nuclear charge
aka core charge is a measure of the attractive force felt by the valence shell electrons to the nucleus
how to calculate effective nuclear charge
number of protons - number of total inner-shell electrons
effective nuclear charge down a group
remains constant but valence electrons are held less strongly as they are further away from the nucleus
effective nuclear charge across a period
increases, group is equal to effective nuclear charge
electronegativity
the ability of an atom to attract electrons towards itself when forming a chemical bond, a measure of how strongly an atom pulls on the electrons of nearby atoms
when does electronegativity not apply
for the noble gases group 18, because the elements have a stable outer shell and wont readily form bonds
trend in electronegativity down a group
decreases as shell number increases so electrons are less attracted to the nucleus
trend in electronegativity across a period
increases are no. of shells remain constant but effective nuclear charge increases
atomic radius
the measurement used for the size of atoms, it can be regarded as the distance from nucleus to the valence shell electrons
trend in radius down a group
increases as effective nuclear charge remains constant and shell number increases
trend in atomic radius across a period
decreases as shells remain constant and effective nuclear charge increases, pulling valence shell electrons in more tightly
first ionisation energy
the energy required to remove one electron from an atom of an element
how does one electron being removed occur
when an element is heated, its electrons can move to higher energy shells, if given enough energy an electron can be completely removed, becoming a positive ion
what does first ionisation energy indicate
how strongly the valence electrons are attracted to the nucleus, the stronger the attraction, the more energy required to remove one
trend in first ionisation energy down a group
decreases as effective nuclear charge remains constant, number of shells increases, they are further from the nucleus so less energy is required to remove an electron
trend in first ionisation energy across a period
increases as effective nuclear charge increases and shells remain constant, electrons are strongly attracted to nucleus so harder to remove
what can the knowledge of whether as element is a metal, nonmetal or metalloid help to predict
how the element will react and bond with other elements
reactivity of metals as you go down a group
increases as valence electrons are further away from the pull of the nucleus and can be lost more easily
reactivity of metals across a period
effective nuclear charge increases so metals become less reactive
what is the most reactive metal
francium, bottom left corner
reactivity of non-metals as you go down a group
decreases as effective nuclear charge remains constant but shells increase which causes electrons to be less electronegative so dont pull electrons in as much
reactivity of non-metals across a period
increases as effective nuclear charge increases and shells remain constant
most reactive non-metal
top right fluorine
