APChem Ch 7 ~ Periodic Properties of the Elements

effective nuclear charge

reduced positive charge from screening of core electrons that valence electrons feel

effective nuclear charge trend

- increase across a period

- increases SLIGHTLY down a group

nonbonding atomic radius

half of the shortest distance separating two nuclei during a collision of atoms

- atoms are not bonded (only collided)

bonding atomic radius

or covalent radius

- half the distance between nuclei in a bond

- atoms are bonded (radius overlaps)

trend of atomic radius

- decrease across a period

- increase down a group

Why does atomic radius decrease across a period?

effective nuclear charge/nuclear charge increases and the attractive forces are greater so electrons are closer to nucleus

Why does atomic radius increase down a group?

energy levels increase and so do the number of shells so the size increases

Size of ions

cations - smaller (remove an electron)

anions - bigger (add an electorn)

isoelectronics series

ions that have the same number of electrons

isoelectronic series atomic radius trend

increasing nuclear charge = decreasing ionic radius

ionization energy

minimum energy required to remove an electron from ground state of gaseos atom/ion

IE 1 < IE 2 < IE 3

ionization energy trend

- increases across a period

- decreases down a group

Why does IE increase across a period

since there is an increase in effective nuclear charge

Why does IE decrease down a group

electrons are farther from nucleus

irregularities in IE trend

5a -> 6a : IE in 5a > 6A because in 5A the orbitals are stable and don't want to lose electrons

2a -> 3a: IE in 2a > 3a beacuse orbital is completely filled already

electron affinity

energy change accompanying the addition of an electron

- exothermic so it is negative

electron affinity trend

-increases across a period

-decreases down a group

exceptions in electron affinity trend

- 2A: s sublvl is full (doesnt want another electron)

- 5A: p sublevel is half filled (wants to stay that way to be stable)

- 8A: p sublvl is full (noble gases)

- anions for these elements would be unstable

metallic character trend

decreases across a period

increases down a group

traits of metals

- shiny luster

- malleable/ductile

- solids at room temp

- high melting point

- good conductor

- tend to form cations

- low IE

traits of nonmentals

- tend to form anions bc of large negative electorn affinity

- solid, liquid, gas

-dull, birttle, poor conductor

more negative electron affinity means....

substance is more readily to gain an electron

neutralization reaction

base + acid -> salt + water

metal oxides form ____ in water

bases

(metal hydroxide)

nonmetal oxides form ____ in water

acids

the more metallic,

the more basic the oxide

the more nonmetallic

the more acidic the oxide

akali metal properties

- low densities and melting points

- low IE

- soft, metallic (typical metal properties)

- only found in compounds in nature (reactive to nonmetals and exothermic)

akali metal trends

down a group > melting point decreases, density increases, and IE dec + more exothermic, and radius inc

oxide

Lithium reacts with oxygen to make an oxide

Li + O₂ -> Li₂O

peroxide

sodium reacts with oxygen to form a peroxide

Na + O₂ -> Na₂O₂

superoxide

K, Rb, and Cs (+ Fr) form superoxides

M + O₂ -> MO₂

akaline earth metals properties

* Be doesn't react with water and Mg only reacts wth steam (gas)

akaline earth metal trends

down a group > IE dec, reactictity dec, melting point dec, density inc, and radius inc

akaline earth metals reactions

Ca, Sr, Ba, + Ra react with water to form H₂ gas, metal hydroxide, and energy/heat

Ca + H₂O -> H₂ + Ca(OH)₂ + en

trend from group 1A -> 2A

- melting point inc

- density inc

- hardness inc

- reactivity dec (akali metals more reactive)

group 6A (the oxygen group)

- O, S, and Se are nonmetals

- Te is a metalloid

- Po (radioactive) is a metal

group 6A trends

- down a group < density inc, IE dec, radius inc

- oxygen is likely to form -2 anion

- polonium (Po) is likely to have a positive charge

halogens (7A)

- typically nonmetals

- highly negative electron affinities > exsist as anions in nature

- directly react w/metals to form metal halides

halogens trends

down a group > density inc, melting pt inc, IE dec, radius inc

allotropes of oxygen

noble gases properties

- relatively unreactive

- monatomic gases

- electron affinities positive (can't form stable anions)

- very high IE

noble gas trends

down a group > density inc, boiling point inc, radius inc, IE dec

hydrogen

- as nonmetal > hydride > -1 anion (ex: NaH)

- as metal > +1 (ex: HCl)

electronegativity