Chapter 2.3 Flashcards
What is the definition of the effective nuclear charge? How does it change across the same period? How does it change down a group?
- it is electrostatic attraction between valence shell electrons and the nucleus
- > it is a measure of positive charge experienced by outermost electrons
- for elements in the same period
- > Zeff increases across the period
- for elements in the same group
- > Zeff decreases as you go down a group
- > more seperation between nucleus and outermost valence energy level
- > as there are more filled principle energy levels or inner shells separating the nucleus from the valence energy level
- > go down a group and shielding of inner shells cancels out the pull of the positive charge from the nucleus
What is the atomic radius equal to? How does it change across a period? How does it change down a group?
-it is equal to one-half the distance between the centers of two atoms in contact with another
- across a period
- > it decreases
- > as Zeff increases and there is more pull on outermost valence electrons to come inward
- down a period
- > number of energy levels increases
- > so that means valence electrons are further out
- > atomic radius increases as you go down a group
What is ionization energy or ionization potential? Is it an endothermic process or an exothermic one? Describe the trend seen in IE across a period and down a group.
- it is the energy required to remove an electron from a gaseous species
- > removing an electron from an atom requires energy
- > so this is an endothermic process
Across a period
->ionization energy increases(Zeff increases)
Down a group
->ionization energy decreases(Zeff decreases)
How does ionization energy change for an atom as more electrons are removed? Show an example of an ionization energy equation for magnesium. Show the first two electrons being removed
-it increases
Mg(g) —> Mg+(g) + electron
Mg+(g)—-> Mg2+(g) + electron
What are active metals? What are their ionization energies like?
- elements in groups 1a and 2a are active metals
- > they have low ionization energies
- > do not exist naturally in their neutral forms
- > found in ionic compounds, minerals or ores
What is electron affinity? Is it an exothermic or endothermic process? What is the trend across a period or down a group? What about that of noble gases
- it is the energy released by a gaseous species when it gains an electron
- > it is an exothermic process
- across a period
- > electron affinity increases
- down a group
- > electron affinity decreases
noble gases
- > they have electron affinities on the order of zero
- > because they already possess a stable octet
What is electronegativity? How does it change across a period and down a group?
- measure of attractive force that an atom will place on an electron in a chemical bond
- related to ionization energies
- > lower the ionization energy, lower the electronegativity
Across a period
->electronegativity increases
Down a group
->electronegativity decreases
