Chp. 2 The Periodic Table Flashcards
Accounts for ~10% of questions in the Chemistry section for the MCAT.
What is the periodic law?
The chemical and physical properties of the elements are dependent upon their atomic numbers
What are A elements?
- Representative elements
- Include groups IA-VIIIA
- Their valence e- are in either s or p orbitals
What are B elements?
- Nonrepresentative elements
- Include transition elements and lanthanide and actinide series
- Their valence e- are in s and d (transition) and s and f orbitals
Characteristics of metals
- Found on the left and middle of periodic table
- Include active and transitional metals and lanthanide and actinide series
- High melting points and densities
- Very malleable; ductility
- Good conductors
Characteristics of nonmentals
- Found on the upper right side of the periodic table
- Brittle in solid state
- Poor conductors
- Don’t easily give up e-
Characteristics of metalloids
- Electronegativities and ionization energies lie b/w *metals and nonmetals
- Physical properties (boiling point, density, etc) vary
- Reactivities depend on what they’re reacting with
What is the effective nuclear charge (Zeff)?
- The electrostatic attraction between the valence e- and the nucleus. It measures a net positive charge.
- Increases L to R in a period
- Remains constant within a group
What happens when you move down the elements of a given group?
- The principal quantum number increases by 1
- Valence e- separate from the nucleus more and more
- Electrostatic attraction is reduced b/w valence e- and nucleus
- Valence e- aren’t held as tightly
What is the atomic radius?
- Half of the distance between the centers of two atoms of an element
- Decreases from L to R
- Increases top to bottom
- Largest atom is Cs in group 1A (1) and smallest is He
- Half of the distance b/w the nucleus and valence e- of an ion
- Nonmetals closer to the metalloid line have a larger radius
- Metals closer to the metalloid line have a smaller radius and have fewer e- to lose
What is the ionic radius?
What is ionization energy?
- The energy required to remove an electron from a gaseous species
- Endothermic process
- Increases L to R
- Decreases top to bottom
- Elements in the groups 1 and 2 are low in this and are called active metals
What are the first and second ionization energies?
- First: the energy needed to remove the first electron; will always be smaller than the second
- Second: the energy needed to remove the second electron from the univalent cation (X+) to form the divalent cation (X2+); larger for group IIA
- The energy given off by a gaseous species when it gains an electron
- Exothermic process
- Increases L to R
- Decreases top to bottom
- Groups 1 and 2 are low in this; group 17 is high in this *Noble gases’ value in this is 0
- Metals are low in this
What is electron affinity?
- A measure of the attractive force that an atom will put on an electron in a chemical bond
- When this increases, the more electrons will be attracted within a bond
- When ionization is low/high, this is low/high
- Increases L to R
- Decreases top to bottom
What is electronegativity?
What increases from left to right on the periodic table?
Ionization energy
E- affinity
Electronegativity
What decreases from left to right on the period table?
Atomic radius
What increases from top to bottom on the periodic table?
Atomic radius
What decreases from top to bottom on the periodic table?
Ionization energy
E- affinity
Electronegativity
Characteristics of alkali metals
- Group 1
- Possess physical properties of metals except density
- Have only 1 loose valence e-
- Easily lose 1 e- to form univalent cations
- Ready to react with nonmetals, esp. halogens
- Have a violent reaction to water
- Known as an active metal
Characteristics of alkaline earth metals
- Group 2
- Share most characteristics of alkali metals
- Slightly larger Zeff, so slightly smaller atomic radii
- 2 easily removable valence e- to form divalent cations
- Known as an active metal
Characteristics of chalcogens
- Group 16
- Nonmetals and metalloids
- 6 valence e-
- Small atomic radii, large ionic radii
- Oxygen is the most important in this group
- At high concentrations, elements in this group can be toxic
Characteristics of halogens
- Group 17
- Highly reactive nonmetals
- 7 valence e-; desperately need to gain an e-
- Variable physical properties
- High electronegativities and e- affinities
- Flourine has the highest electronegativity of all elements
- Typically found as ions (halides) because they’re so reactive
Characteristics of noble gases
- Group 18
- Minimal chemical reactivity
- High ionization energies
- Don’t really tend to lose/gain e-
- Low boiling points
Characteristics of transition metals
- Groups 3-12
- High melting and boiling points
- Malleable, good conductors
- Loosely held valence e- that fill the “d” orbital
- Can have several oxidation states (possible charged forms)
- Form many different compounds and complex ions
- Low effective nuclear charge
- Low electronegativity
- Low e- affinity
- Large atomic radius, small ionic radius
Periodic trends for metals
- Easily give up e-
* Valence e- are free to move
Electron activity for metals
- High ionization energies, e- affinities, and electronegativies
- Small atomic radius, large ionic radius
Periodic trends for nonmetals
What elements are metalloids?
Boron (B), Silicon (Si), Germanium (Ge), Arsenic (As), Antimony (Sb), Tellurium (Te), Polonium (Po), and Astatine (At)
- Low Zeff, ionization, e- affinities and electronegativities
- Largest atomic radii
Periodic trends for alkali metals
What group is especially reactive towards alkali and alkaline metals
Halogens
*Low e- affinities, ionization energies and electronegativities
Periodic trends of transition metals
