quiz #3 Flashcards
elements in groups exhibit…
similar chemical behaviour
why doe elements in groups exhibit similar chemical behavior?
members of a group have the same number and distribution of valence electrons
the physical and chemical behavior of elements is ultimately based on what?
the electron configuration of their atoms
definition of atomic radii
distance between electrons and nuclei
definition of metallic radii (used for metals)
1/2 the distance between 2 atoms in a crystal of the element
atomic size
1/2 the distance between nuclei of identical covalently bonded atoms
explain changes in the principle quantum number (n)
atoms become larger as “n” increases - the probability that the outer electrons will spend more time farther from the nucleus increases
explain changes in Zeff
atoms become smaller as Zeff increases - as effective nuclear charge increases, outer electrons are pulled closer to the nucleus
what is Zeff
effective nuclear charge, it is how much an electron feels the pull of protons in the nucleus (therefore, more protons = more pull)
explain how n increases on the periodic table
n increases down a group (more electrons = larger orbitals), so atoms become larger
explain how Zeff increases on the periodic table
Zeff dominates across a period as protons increase, and electrons feel a greater pull from the nucleus (atoms become smaller)
what causes changes in atomic size?
changes in principle quantum number, changes in Zeff
atomic size in transition elements
shielding by inner d-electrons counteracts the increase in Zeff, so size remains relatively constant across a period
ionic size vs atomic size - cations
cations are smaller tha their parent ions: electron repulsion decreases, Zeff increases
ionic size vs atomic size - anions
anions are larger than their parent atoms: electron repulsion increases so they take up more space
define ionization energy
the energy in kJ require for the complete removal of 1 mol of electrons from 1 mol of gaseous atoms/ions
simplify ionization energy
taking an electron away, making the atom POSITIVE
general trend for ionization energy:
as size decreases, it takes more energy to remove an electron = higher ionization energy
what are the exceptions/anomalies for ionization energy?
B has lower IE than Be; O has lower IE than N
why doesn’t IE decrease between Al and Ga?
due to the increased Zeff in Ga; 4p orbitals penetrate more than 3d so the electrons in Ga feel a much larger Zeff than in Al
define electron affinity
energy change in kJ accompanying the addition of 1 mol of electrons to 1 mol of gaseous atoms/ions
what is the EA trend for reactive metals?
group 1A and 2A have low IE and slightly positive EA - they form positive ions
what is the EA trend for reactive nonmetals?
group 6A and 7A form negative ions
explain EA on the periodic table
it decreases down a group (with many exceptions) and increases along a period
