Ch. 7 notes

See p. 205 “Chapter 7 Study Guide” for the main points.

From Ch. 6 Octet Rule

· Atoms tend to gain lose or share e- in order to acquire a full set of 8 val. e- (except H, which only needs 2)

· Alloy- solid metal solution (mixture)

· Metals and Non-Metals have different trends in reactivity.

p. 180 Metals (lose val. e-)

· moving down a group IE decreases

· that means it is easier to lose e-

· that means REACTIVITY increases

example: Fr is the most reactive alkali metal

p. 180 Non-metals –

· gain e- to fill the valence

· that means the higher the IE ( & EN) then the MORE REACTIVE it is

· that means REACTIVITY decreases as you go down the group (F is most reactive nonmetal) (See EN values on p. 169)

Diagonal relationships- see p. 180

p. 180 Hydrogen

H₂ gas burns when exposed to air (Hindenburg)

2 H₂ + O₂ → 2 H₂O(g) + heat

3 isotopes (different forms of same element, with differing numbers of neutrons): H-1_, H-2 & H-3 (named protium, deuterium, tritium respectively) Most hydrogen is H-1.

Hydrogen is sometimes like a metal (loses its e-), and sometimes like a non-metal (gains an e-)

Group 1A alkali metals

Lose 1 val e- forms +1 charge

Group 2A

Solids

Harder, shiny, less reactive

Lose 2 val e-, forms ions with +2 chg

calcium carbonate CaCO₃ – limestone,chalk, antacids

Mg-

Sr-

7.2 p-block wide variety of properties

B- used in borosilicate glass (pyrex)

Borax (cleaner); Boric acid-eye wash, and roach poison

Al- most abundant metal in earth’s crust; cans;

Ga- used to make blue lasers, which are in Blue-ray DVD players

Group 4A

C- organic chemistry; C is found in every living thing.

Allotropes- diamond & graphite;

Definition-diff. forms of an element that have diff. structures & properties

Si- 2^nd most abundant element in Earth’s crust; found in SiO₂ (sand);

Ge- used in semiconductors; transistors in electronics

Sn- tin cans

Pb- toxic; used in leaded gasoline, lead pipes; lead paint, batteries;

Group 5A Nitrogen

5 val. e- (gains 3 e- to form ions with 3- charge)

N- 78% of atmosphere is N₂ gas; explosives (TNT), fertilizers (NH₃ ammonia), in body (proteins)

P- found in fertilizers and laundry detergents

Group 6A Oxygen p. 192

Oxygen is the most abundant element in Earth’s crust.

Oxygen has 2 allotropes (different forms of same element, with differing structures & properties):

O₂ & O₃

O₂ oxygen gas makes up 21% of our atmosphere; diatomic molecule; reacts with/forms bonds with every element on the PT except noble gases.

O₃ ozone; triatomic molecule; less stable than O_2; it is a pollutant in the lower atmosphere (irritates lungs, eyes, & plants), but beneficial in the upper atmosphere (protects Earth from harmful UV radiation)

Sulfur- 10 allotropes;

S + O₂ SO₂ (sulfur dioxide -in acid rain)

Sulfuric Acid – in fertilizers, battery acid

Hydrogen Sulfide gas- gas from ocean vents & volcanoes

Group 7A Halogens-

“salt formers” – form salts when combined with metals

F- most active element; in toothpaste & city water

Cl-bleach, disinfectant, hydrochloric acid (stomach acid); also used in industry (PVC & plastics)

I-needed by thyroid; solid that sublimes;

Br-only liquid non metal

Group 8A- Noble Gases

Virtually unreactive due to full valence;

He- sun (2 H’s fuse to form He)

Ne-neon signs

Ar-most abundant noble gas on Earth

Transition metals- can form ions +2 +6

Across the period little variation in size, EN, & IE

But- they have diff. phys. Properties due to the ability of unpaired e- to move into the valence level;

(the more unpaired e- in the d sublevel, the harder the metal is & the higher the MP)

Ferromagnetic Metals- Fe, Co, Ni (can form permanent magnets)

Lanthanides-silvery metals, high MP

Actinides- all radioactive

Misc.

Earths crust: Top 3 elements: O, Si, Al

Fertilizer: N-P-K for example 15-5-10 has 10% K