the periodic table - welcome students · intro to the periodic table ... developed a version of the...

The Periodic Table

Intro to the Periodic Table

Intro to the Periodic Table

Intro to the Periodic Table

Dobereiner:

Developed ‘triads’ that

groups elements based on

common characteristics.

No arrangement between

triads, however.

Dmitri Mendeleev

Mendeleev:

Developed a version of the periodic table of elements that reflected patterns and properties.

Biggest contribution: leaving blank spaces predicting elements (and their properties) that had yet to be discovered!

Intro to the Periodic Table

In 1913 Henry Mosely (along with Rutherford)discovered the idea of positive charge within thenucleus. Discovered each element had a certain

amount of positive charge in the center. Called these whole number positive charges

atomic number. Determined the atomic number of all known

elements at that time.

B. Moseley

Mosely: Arranged the periodic table in order of

increasing atomic number.

- This is the way the table is

currently arranged.

- Remember # of protons =

atomic #

Intro to the Periodic Table

Periodic Law: The properties of elements are

periodic – that is a repeating pattern of chemical

and physical properties. (they repeat in a

systematic way)

Key Idea

For example, which elements are similar to sodium?

Elements in the same group have similar properties.

This is because they have the same # of valence

electrons!

Intro to the Periodic Table

Valence Electrons:

Outermost electrons in an atom (responsible for

properties of an element).

Intro to the Periodic Table

Example: State the valence electrons for the

Following elements.# of valence electrons

Li Mg Al O Cl Ne

Lewis Dot Diagram

Periodic TrendsValence electrons and group properties:Each element in a group has similar properties, due to all members

having the same number of valence electrons.

Metals: Nonmetals:

Form (+) ions Form (-) ions

Lose electrons Gain electrons

Group 1 Group 2 Groups 3-12 Group 13 Group 14 Group 15 Group 16 Group 17 Group 18

1 Valence Electron

2 Valence Electrons

Varies 3 Valence Electrons

4 Valence Electrons

5 Valence Electrons

6 Valence Electrons

7 Valence Electrons

8 Valence Electrons

+1+2 Varies +3 +/- 4 -3 -2 -1 No Ions

Ever wonder what people who like science and

music do in their spare time?

https://www.youtube.com/watch?v=VgVQKCcfwnU

Groups of the Periodic Table

http://periodictable.com/index.html

Groups of the Periodic Table

Hydrogen:

Has 1 valence electron, so it

is placed with

group1 but it is NOT a

metal. One of the more

common elements in the

universe.

Groups of the Periodic Table

Alkali Metals:

Very reactive, explosive metals (often grey, soft).

1 valence electron and forms +1 ions.

Alkali Metal Reactivity

Reactivity with air & water:

http://www.youtube.com/watch?v=uixxJtJPVXk&safety_mode=true&persist_safety_mode=1&safe=active

Brainiac’s play with alkali metals:

http://www.youtube.com/watch?v=m55kgyApYrY&safety_mode=true&persist_safety_mode=1&safe=active

Groups on the Periodic Table

Alkaline Earth Metals:

Reactive metals, tend to be found in compounds

in nature. 2 valence electrons and forms +2 ions.

Groups on the Periodic Table

Transition Metals:

Stable metals. Can form

more than one (+) ion

b/c they can change the #

of electrons lost. They

form colorful (+) ions

when in a solution.

Groups on the Periodic Table

Lanthanide Series:

4f block of elements

Actinide Series: 5f block of

elements. Almost all

are man-made, all are

radioactive.

Groups of the Periodic Table

Halogens:

Reactive nonmetals.

Group contains all 3 states

of matter (s,l,g). Mainly

form -1 ions b/c they

only need 1 valence

electron to achieve octet.

Reactivity of Halogens:

http://www.youtube.com/watch?v=u2ogMUDBaf4

Groups of the Periodic Table

Noble Gases:

Stable valence electron configuration, which

means they are nonreactive – they have a full

octet (remember that # is 2 for He, but 8 for the

rest of the group.)

Group 13

+3 Ion

Group 14

+/- 4 Ion

Group 15

-3 Ion

Group 16

-2 Ion

Groups of the Periodic Table

Metals SemimetalsMetalloids

Nonmetals

Malleable, ductileShiny (luster)Lose electrons = (+) ionsGood conductorsOnly liquid: Hg (rest are solid)

7 total (on step line)B, Si, Ge, As, Sb, Te, At

Properties are in between metals and nonmetals

BrittleNonconductorsGases, liquid (Br), and solidsGain electrons = (-) ions

The Octet Rule:

Atoms will lose, gain or

share electrons to achieve

stability – a full octet of 8

valence electrons.

Metals accomplish this by

losing electrons.

Nonmetals gain electrons

to fill the valence shell.

Exception: 1st PEL only

holds 2 electrons.

As you move across a period:

- # of PEL’s stays the same

- # of protons increases

- # of e- in the valence shell increases

which increases attraction.

Coulombic attraction increases b/c

atomic radius decreases.

As you move across a period the # of

protons increases & the # of e- in the

valence shell increases, which

increases attraction.

Coulo

mbic

att

ract

ion d

ecre

ases

b/c

ato

mic

rad

ius

incr

ease

s. I

ncr

ease

in #

of

PE

L’s

cau

ses

e-to

be

fart

her

fro

m

the

nucl

eus

dec

reas

ing a

ttra

ctio

n.

Coulo

mbic attractio

n in

creases b/c

atom

ic radiu

s decreases.

As y

ou m

ove acro

ss a perio

d th

e # o

f

pro

tons in

creases & th

e # o

f e-in

the

valen

ce shell in

creases, which

increases attractio

n.

Coulombic attraction decreases b/c

atomic radius increases. Increase in #

of PEL’s causes e- to be farther from

the nucleus decreasing attraction.

Periodic TrendsPeriodic Trends:

Predictable patterns across the periodic table

(atomic radius, metallic character, ionization

energy, electronegativity) and down the groups.

Atomic Radius:

Across a period:

Get Smaller

Down a group:

Get Larger

Metallic Character:

How much an atom acts

metallic – i.e. how easily it

loses electrons.

Across a period:

Decreases ( you are heading

towards the nonmetals)

Down a group:

Increases (easier to lose an

electron if the atom is

bigger).

* Most metallic elements are in the lower left corner.

+ ion:

Loss of an electron

reduces the electron cloud

size. Radius decreases.

- ion:

Gain of an electron

increases electron cloud

size. Radius increase.

Ionization Energy:

Energy to remove

outermost electron

Across a period:

Increase

Down a group:

Decrease

Electronegativity:

Ability to attract an electron

(“affinity for electrons”)

Across a period:

Increase

Down a group:

Decrease