periodic table trends Flashcards
33. Explain how the arrangement of the periodic table is based on the atomic number of the elements. 34. Describe the relationship between position on the periodic table and electronic arrangement, including the relationship between group and number of valence electrons, and between period and number of occupied electron shells. 35. Use electron configuration to identify an atom or ion and its location in the periodic table, and infer its chemical properties. 36. Describe and explain the rel
how is the periodic table arranged
by increasing atomic no. of elements x
what do elements in the same group hv in common
Elements in the same group have the same number of valence electrons in their configuration
Elements in the same group generally exhibit similar chemical properties i.e reactivity as they have the same no. valence electrons - which are responsible for an element’s chemical reactions
what do elements in the same period hv in common
period(row) number corresponds to number of energy shells in the element’s electronic configuration
define atomic radius
the average distance between the outermost electron and the nucleus of the atom
what is the trend in atomic radius as you move right across a period
as you move right across a period
there is an increase in the number of protons (as number of outer shell electrons increase by 1)
however same number of inner shell electrons (as in a period there is the same number of shells) therefore same shielding effect remains constant
therefore increase ”effective nuclear charge”
stronger electrostatic attraction between outermost electrons and nucleus
outermost electron is held more closely to nucleus - decrease in avg distance between them
therefore decrease in atomic radius
what is the trend in atomic radius as you move down a group
as you move down a group…
there is an additional principle energy level further from the nucleus
the outermost electron is therefore further away from the nucleus
increase in avg distance between outermost electron and nucleus
therefore increase in atomic radius
define (first) ionization energy
the amount of energy required to remove 1 mol of the outermost electron from 1 mol of an element in its gaseous to form 1 mol of ions
what is the trend in first ionization energy as you move down a group
as you move down a group…
there is an additional principle energy level (shell) further from the nucleus
the outermost electron is therefore further away from the nucleus
weaker electrostatic attraction between outermost electron and nucleus
less energy (easier) required to remove outermost electron
therefore decrease in ionisation energy
what is the trend in first ionization energy as you move right across a period
as you move right across a period
there is an increase in the number of protons
however same number of inner shell electrons
therefore same shielding effect but increase number of protons
increase in ”effective nuclear charge”
stronger electrostatic attraction between outermost electrons and nucleus
increase in amount of energy required to remove outermost electron
increase in ionisation energy
define electronegativity
ability of an atom to attract a shared, bonding pair of electrons when forming a chemcial (covalent) bond
what is the most electronegative elements
N < O < F
what is the trend in electronegativity as you move down a group
as you move down a group…
there is an additional principle energy level (shell) further from the nucleus
the outermost electron is therefore further away from the nucleus
increase in avg distance between bonding pair and nucleus (increase in AR)
incoming electrons can therefore not approach nucleus as closely
weaker electrostatic attraction between incoming electrons and nucleus
therefore decrease in electronegativity
what is the trend in electronegativity as you move right across a period
as you move right across a period
there is an increase in the number of protons
however same number of inner shell electrons therefore same shielding effect
increase in ”effective nuclear charge”
stronger electrostatic attraction between outermost electrons and nucleus
outermost electron is held more closely to nucleus - decrease in avg distance between bonding pair and nucleus (decrease in AR)
incoming electrons can approach nucleus more closely
stronger electrostatic attraction between incoming electrons and nucleus
therefore increase in electronegativity (exception of noble gases which are unreactive so generally have 0 electronegativity)
group 1
alkali metals
group 2
alkali earth metals
