AP Chem - Periodic Table Unit

Unit #4

Where are metals located?

on the left side of the periodic table

What are the properties of metals?

• good conductors (heat and energy)

• malleable (hammered into thin sheets)

• ductile (shaped into wires)

• shiny

• they have a “sea of free moving electrons”

• usually lose electrons

Where are nonmetals located?

on the right side of the periodic table

What are the properties of nonmetals?

• good insulators

• opposite physical properties of metals (dull, brittle)

• usually gain electrons

• form ionic bonds with metals & covalent bonds with nonmetals

Where are metalloids located?

on the “staircase”

What are the properties of metalloids?

they have weak properties of both metals and nonmetals

What is a group?

the vertical columns of a periodic table

What do elements in a group have in common?

same # of valence electrons, physical, and chemical properties

What is a period?

the horizontal rows of a periodic table

What do elements in a period have in common?

same # of PELs

What are group 1 elements called?

alkali metals

What are group 2 elements called?

alkaline earth metals

What are group 17 elements called?

halogens

What are group 18 elements called?

noble gases

What are group 3-12 elements called?

transition metals

What is an allotrope?

different forms of an element in the same physical state

ex: graphite and diamond are allotropes of carbon

Do allotropes have the same physical and/or chemical properties?

no because they differ in molecular/crystal structure

What are the seven diatomic elements? What are their phases at room temp?

H (gas), O (gas), Br (liquid), F (gas), I (solid), N (gas), Cl (gas)

What is effective nuclear charge?

the net positive charge that a valence electrons feels

How is shielding and effective nuclear charge related?

as shielding increases, the effective nuclear charge decreases due to weaker nuclear attraction

Who arranged the first periodic table?

Mendeleev

Who discovered that elements are characterized by their atomic number and not their atomic mass?

Moseley

What is atomic radius?

half the distance between the nuclei of two identical atoms

What is the trend for atomic radius for a group?

the atomic radius increases due to the addition of another PEL as you go down a group

What is the trend for atomic radius for a period?

• the atomic radius decreases because electrons are more attracted to the nucleus

• since the amount of protons increase and electrons are added to the same PEL, electrons feel a stronger pull from the nucleus

Which elements have a pretty “constant” atomic radius?

transition metals → since they fill the d orbital, there will not be a significant change in the atomic radius

What is ionization energy?

the amount of energy required to remove an electron from a gaseous atom

What is second ionization energy?

the energy required to remove the second outermost electron

Why does it require more energy to remove each successive electron?

when an electron is removed, the (+) charge increases, resulting in the electrons having a stronger nuclear attraction (harder to remove)

What is the difference between the IE of valence electrons and the IE of core electrons?

there is a significant difference between the IE of valence electrons and core electrons (valence e- requires less energy)

What is the trend of ionization energy for a group?

IE decreases because there is increased shielding due to the addition of another PEL (easier to remove)

What is the trend for ionization energy for a period?

IE increases due to the increase in nuclear attraction

What is electronegativity?

the ability of an atom to attract shared electrons to itself

Is electronegativity a measure of energy?

no

What are the possible values for electronegativity?

values range from 0.7 - 4.0

Which group do not have electronegativity values?

group 18 (noble gases) because they usually do not form bonds due to their full valence electron shell

What is the trend for electronegativity for a group?

EN decreases because there is a weaker nuclear attraction

What is the trend for electronegativity for a period?

EN increases because there is stronger nuclear attraction

What does electronegativity tell us about bonding?

whether or not an element is likely to receive or accept an electron when bonding

What is electron affinity?

the energy change associated with the addition of an electron to a gaseous atom

Describe the electron affinity for metals

since metals tend lose electrons, adding an electron goes against the nature of the metal, which means it will require a lot of energy to do so (endothermic)

Describe the electron affinity for nonmetals

since nonmetals tend to gain electrons, it will not require energy to add an electron, which means its exothermic

What is the trend for electron affinity for a group?

decreases (less negative, more endothermic)

What is the trend for electron affinity for a period?

increases (more negative, more exothermic)

What is ionic radius?

determined from the measured distance between ion center in an ionic compound

What happens to the size of an atom when it becomes an cation?

it decreases

What happens to the size of an atom when it becomes an anion?

it increases