Chapter 9: Periodic Properties of the Elements

s

# of electrons in the lower energy levels

What is the Zeff valence electrons of the following elements? - Na - Mg - Al - P - Cl

- Na > +1 - Mg > +2 - Al > +3 - P > +5 - Cl >+7

Pail Exclusion Principle (PEP)

- No two electrons in an atom may have the same set of 4 quantum numbers - Therefore, no orbital may have more than two electrons, & they must have opposite spins

Periodic Law

- When the elements are arranged in order of increasing atomic mass, certain sets of properties recur periodically - Put elements with similar properties in the same column

Electron spin quantum number, ms

-1/2 (down) or +1/2 (up)

L is also the orbital shape

0 = s 1 = p 2 = d 3 = f

Diamagentism

Electron configurations that result in all paired electrons mean that the atom or ion will have no magnetic field

Paramagnetism

Electron configurations that result in unpaired electrons mean that the atom or ion will have a net magnetic field

Core electrons

Electrons in lower energy shells

The Electron Configuration of Halogens (electrons)

Halogens have one fewer electrons than the next noble gas

Covalent radius

bonding

d

d sublevel has 5 orbitals; therefore, it can hold 10 electrons

Atomic radius ___ along period (left to right)

decreases - Effective nuclear charge increases - Valence shell held closer

Coulomb's law

electric force between charged objects depends on the distance between the objects and the magnitude of the charges.

For sublevels the energy also increases as the Quantum number increases

s (L = 0) < p (L = 1) < d (L = 2) < f (L = 3)

s

s sublevel has 1 orbital; therefore, it can hold 2 electrons

Cations are __ than neutral atoms; anions are ___ than neutral atoms

smaller larger

Larger positive charge =

smaller cation

The direction of the arrow represents

spin of the electron

The Quantum-mechanical model

the modern description, primarily mathematical, of the behavior of electrons in atoms

For primary shells the energy increases as the quantum number increases

1n < 2n < 3n < 4n...

1s ...

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d

Electrons are more strongly attracted to a nucleus with a ___ charge than a nucleus with a ___ charge

2+ 1+

Quantum mechanics

A theory that explains the why the periodic trends in the properties exist.

Which atom in each pair has the larger atomic radius? - Al or B - S or O - Br or Cl - Na or Al - O or F - Mg or Ca

Al S Br Na O Ca

Aufbau Principle

An electron occupies the lowest-energy orbital that can receive it then moves higher

Which of the following statements is FALSE? - Two electrons in the same orbital can't have the same spin - An orbital that penetrates into the region occupied by core electrons is more shielded from nuclear charge than an orbital that does not penetrate and therefore has a lower energy. - It is not possible for two electrons in the same atom to have identical values for all four quantum numbers - An orbital that penetrates into the region occupied by core electrons is less shielded from nuclear charge than an orbital that does not and therefore has a lower energy. - None of the above is false.

An orbital that penetrates into the region occupied by core electrons is more shielded from nuclear charge than an orbital that does not penetrate and therefore has a lower energy.

Electron configuration of anions

Anions are formed when nonmetal atoms gain enough electrons to have eight valence electrons - Filling the s & p subshells of the valence shell

The closer an electron is to the nucleus the more ... it experiences

Attraction

The orbitals orientation in space quantum number, m

B/e -L & +L

Which atom in each group (I and II) has the smallest atomic radius? (I) Ca, Ti, Br (II) O, S, Se

Br; O

Electron configuration of cations

Cations are formed when a metal atom loses all its valence electrons, resulting in a new lower energy level valence shell

The element that corresponds to the electron configuration 1s2 2s2 2p6 3s2 3p6 4s1 3d5 Iron Titanium Vanadium Manganese Chromium

Chromium

Choose the statement that is TRUE. - Outer electrons efficiently shield one another from nuclear charge. - Core electrons effectively shield outer from nuclear charge. - Core electrons are the easiest of all electrons to remove. - Valence electrons are most difficult of all electrons to remove. - All of the above are true.

Core electrons effectively shield outer from nuclear charge.

The Electron Configuration of Halogens (reactions with metals)

In their reactions with metals, the halogens tend to gain an electron & attain the electron configuration of the next noble gas, forming an anion with a charge of 1-

The Electron Configuration of Halogens (reactions with nonmetals)

In their reactions with nonmetals, they tend to share electrons with other nonmetals so that each attains the electron configuration of a noble gas

The Electron Configuration of Alkaline Earth Metals (reactions)

In their reactions, the alkali earth metals tend to lose two electrons, resulting in the same electron configuration as a noble gas - Forming a cation with 2+ charge

The Electron Configuration of Alkali Metals (reactions)

In their reactions, the alkali metals tend to lose one electron, resulting in the same electron configuration as a noble gas. - Forming a cation with a 1+ charge

Of the following, which atom has the smallest atomic radius? Co Ca Ti Kr

Kr

Angular Momentum Quantum Number or subshell, L

L = < (n-1) starting at 0

Why do elements have different or similar properties?

Mendeleev's periodic law allows us to predict what properties of an element will be based on its position on the table.

Orbital diagrams

Orbital diagrams use a square to represent each orbital & a half arrow to represent each electron in the orbital

___ don't effectively screen for each other

Outer electrons

___ are shielded from the nucleus by the ___

Outer electrons core electrons

Atom gain e-

Radius is bigger (-)

Atom lose e-

Radius is smaller

Place the following elements in order of decreasing atomic radius. Cd Rb Xe

Rb > Cd > Xe

The Electron Configuration of Alkali Metals (electrons)

The alkali metals have one more electron than the previous noble gas

The Electron Configuration of Alkaline Earth Metals (electrons)

The alkaline earth metals have two more electrons than the previous noble gas

Valence electrons

The electrons in all the sublevels with the highest principle energy shell

The Electron Configuration of noble gases (valence e-)

The noble gases have 8 valence electrons. Full sheets for each level. - Except He, only 2 e-

Why are noble gases so nonreactive?

The reason the noble gases are so nonreactive is that the electron configuration of noble gases is especially stable, because each shell is completely full there is no open orbitals for an electron to occupy.

The Electron Configuration of noble gases (reactive or nonreative)

They are especially nonreactive - He and Ne are practically inert

Electron configuration of transition metal cations

When transition metal cations, the first electrons are removed are the valence electrons (highest n#), even though other electrons were added after - The iron atom has two valence electrons: Fe atom = 1s2 2s2 2p6 3s2 3p6 4s2 3d6 - When iron forms a cation, it first loses its valence electrons: Fe2+ cation= 1s2 2s2 2p6 3s2 3p6 3d6

Z eff =

Z -s

Give the ground state electron configuration for As. [Ar] 4s2 3d10 4p6 [Ar] 4s2 3d10 4p3 [Ar] 4s2 3d10 [Ar] 3d10 4p4 [Ar] 4s2 4p10 4p3

[Ar] 4s2 3d10 4p3

Give the ground state electron configuration for Sr. [Kr] 5s2 4d10 [Kr] 5s2 4d10 5p2 [Kr] 5s2 5d10 5p2 [Kr] 5s2 4d10 [Kr] 5s2

[Kr] 5s2

f

f sublevel has 7 orbitals; therefore it can hold 14 electrons

The ___ corresponds to the # of valence electrons

group #

Atomic radius ___ down groups.

increases - Valence shell further from nucleus - Effective nuclear charge fairly close

Larger negative charge =

larger anion

A cation of +2 indicated that an element has - lost two protons - lost two electrons - gained two protons - lost two neutrons - gained two electrons

lost two electrons

4s is ___ in energy than 3d

lower

5s is ___ in energy than 4d

lower

6s is ___ in energy than 4f & 5d

lower

Principle Quantum Number, n

n is an integer starting at 1

Van der Waals radius

nonbonding

The shielding causes the outer electrons to not experience the full strength of the ___

nuclear charge

Z

nuclear charge

Degenerate

orbitals with the same energy

The better an ___ is at penetrating though the electron cloud of ___, the more attraction it will have for the nucleus

outer inner

p

p sublevel has 3 orbitals; therefore, it can held 6 electrons

The ___ corresponds to the principle energy level of valence electrons

period #