Lesson 3 - Trends in the Periodic Table Flashcards
Atomic radius
is the distance from the nucleus to just beyond the outermost electrons (valence electrons)
Within a period … The # of energy levels stays the…
same
Within a group… The # of Valence e- stays the…
same
Atomic radius: Left-to-right in a period:
More protons in the nucleus for same number of energy levels = the ENC increases, stronger attraction between nucleus and electrons = smaller atomic radius
Atomic radius: Top-to-bottom in a group:
Number of energy levels increases = weaker attractive force due to increasing number of shielding electrons = larger atomic radius
How atomic radius works
effective nuclear charge, which is the net force experienced by an electron in an atom due to the positively charged nucleus
Arrange Xe,Rb,Sr in largest to smallest atomic radius
Rb, Sr, Xe
Ionic radius
Size of atom after ion formation depends on whether a cation (+) or anion (-) was formed
Cations are always_____ than their original neutral atoms
smaller
Cation has one less energy level than the neutral atom
The same ENC is now shared among less electrons, so force is slightly higher on each one; nucleus pulls the electrons more closely
Anions are always_____ than their original neutral atoms
bigger
The same ENC is now shared among more electrons, so force is slightly weaker on each one; nucleus cannot hold electrons quite so close
Ionization Energy
Ionization energy is the amount of energy required to remove an electron from an atom or ion in the gaseous state
What does the amount of energy used for ionization energy depends on what?
on which electron is being removed
Ionization Energy repped in a equation
X (g) + energy —> X+ (g) + e-
Ionization Energy left-to-right across a period
increase
ENC increases, so valence electrons are more strongly attracted to the nucleus, and thus more energy is required to remove an electron from the atom
Ionization Energy top-to-bottom in a group
decrease
Atomic radius increases, so the attraction between the valence electrons and nucleus becomes weaker, and thus less energy is required to remove the first valence electron
Explain which would have a higher ionization energy; sodium or rubidium?
Sodium as they are in the samw group and decreasing.
-Atomic radious is increasing so the attractive forces between the valence electrons and nucles become wekaing thus less energy is need to remove the valence e-
Electron affinity
Electron affinity is the energy change that occurs when an electron is accepted by an atom in the gaseous state
-When an electron is added to a neutral atom in the gaseous state, energy is usually released
Electron affinity repped as a equation
X(g) + e- –> X+(g) + Energy
Electron affinity can also be thougth as
as the amount of energy an atom (or ion) is willing to pay to buy another electron
Electron affinity top-to-bottom in a group
decreases
Atomic radius increases, so there is a weaker attractive force between the nucleus of atom and the new electron, and thus the atom is less willing to spend energy to add an electron
Electron affinity left-to-right across a period
increases
ENC increases, so the force of attraction between the nucleus and the valence electrons increases, and thus the atom is more willing to spend energy to add an electron
HOWEVER Noble gases are an exception!
Which element in each of the following pairs will have a lower electron affinity?
A) S or Se
Se
as when you go down a group electron affinity decreases because the atomic raidus increases so there is a weaker force of attarction between valence e- and nucles so the atom is less willing to spend enegery for new e-
Electronegativity
a way of quantitatively describing the ability of an atom to attract electrons when bonded, combining ionization energies, electron affinity, and some other measures of reactivity
-Linus Pauling came up with this
What element did he assign the value 4.0 to F and why?
assigned a value of 4.0 to fluorine, the element considered to have the greatest ability to attract electrons within a chemical bond
TRUE OR FALSE: , electronegativity IS a measurement
FALSE:
electronegativity is NOT a measurement
Electronegativity generally _____ top-to-bottom in a group
decreases
Atomic radius increases, so there is a weaker attractive force between the nucleus of atom and the new electron, and thus the atom is less willing to spend energy to add an electron
Electronegativity _______ left-to-right across a period
increases
ENC increases, so the force of attraction between the nucleus and the valence electrons increases, and thus the atom is more willing to spend energy to add an electron
Reactivity
Non-metal increasing as it moves form bottom left corner diagnoall across to top right corner
Metlaocs decreases as you go from top rigth corner to bottom left corner
Metallic Reactivity: Reactivity _____ top-to-bottom in a group
increases
ENC stays the same, more electrons are added to farther shells = less hold on electrons 🡪 allows metals to readily give up electrons
Metallic Reactivity: Reactivity _____ left-to-right in a period
decreases
ENC increases, electrons are added to same shell and held tightly = more difficult for metals to give away electron
Non-Metallic Reactivity: Reactivity ___ top-to-bottom in a group
decreases
ENC stays the same, more electrons are added to farther shells = less hold on electrons 🡪 harder for non-metals to gain an electron
Reactivity _____left-to-right in a period
increases
ENC increases, electrons are added to same shell and since electronegativity increases across a period, non-metals will react to gain electrons
The most reactive metals are the ______ since they are the best electron givers.
largest
The most reactive nonmetals are the _____ ones, the best electron takers.
smallest
