Unit 18: Representative Metals, Metalloids, and Nonmetals
What the periodic table's broad regions actually look like in action, from a metal violent enough to be stored underwater to one element wearing two disguises.
5 topics · 17 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
18.1 Periodic Trends in Metallic Character
- How it worksHow does an atom's willingness to lose electrons, tracked by ionization energy and electronegativity, define its metallic character?
- Common mistakeWhy isn't metallic character simply a yes-or-no label instead of a smooth trend across the periodic table?
- Going furtherWhat happens to an element's classification as metal, metalloid, or nonmetal as you move diagonally across the staircase line?
Your turn1 of 2
Cesium and gold are both classified as metals, but cesium reacts violently while gold is nearly inert. Why isn't metallic character simply a yes-or-no label instead of a smooth trend?18.2 Group 1: Alkali Metal Reactivity
- How it worksHow does having just one loosely held valence electron make every alkali metal eager to lose it in a single, violent step?
- Worked exampleFind the balanced equation for the reaction between potassium metal and water, including the gas produced.
- Common mistakeWhy does reactivity increase, not decrease, as you move down the alkali metal group despite the atoms getting heavier?
- Going furtherWhat happens to the vigor of the reaction with water as you move from lithium down to cesium in group 1?
Your turn1 of 2
Lithium, sodium, and potassium all react with water, but the reaction gets more violent going down the group even though the atoms are getting heavier. Why does reactivity increase, not decrease, down group 1?18.7 Group 17: Halogen Reactivity Trends
- How it worksHow does a smaller atomic radius let fluorine pull an extra electron in more strongly than the larger halogens can?
- Worked exampleFind which halogen, chlorine or bromine, will displace the other from a solution of its salt, based on relative reactivity.
- Common mistakeWhy doesn't a halogen's reactivity increase down the group the way an alkali metal's does?
Your turn1 of 2
Chlorine gas is bubbled into a solution containing dissolved bromide ions (Br-). Based on relative halogen reactivity, what happens?18.3 Allotropes of Carbon
- How it worksHow does diamond's rigid three-dimensional network of bonds, versus graphite's stacked flat sheets, produce two wildly different materials from one element?
- How it worksWalk me through how graphite's loosely stacked layers let it slide apart easily and conduct electricity within each layer.
- Common mistakeWhy isn't graphite simply a lower-quality or 'broken' form of diamond?
- Going furtherWhat happens to carbon's bonding pattern in a third allotrope, buckminsterfullerene, compared to diamond and graphite?
Your turn1 of 2
Diamond is extremely hard, while graphite is soft enough to be used as pencil lead, even though both are pure carbon. Why isn't graphite simply a lower-quality or 'broken' form of diamond?18.1 Metalloids and the Periodic Table's Staircase
- How it worksHow does sitting right along the periodic table's diagonal staircase give a metalloid properties that blend metal and nonmetal behavior?
- Common mistakeWhy isn't a metalloid simply a weak or partial metal?
- Ties togetherHow does a metalloid's intermediate conductivity connect back to the band gap separating a semiconductor from a true conductor?
Your turn1 of 2
Silicon, a metalloid, conducts electricity only under certain conditions, unlike a true metal, which always conducts well. Why isn't a metalloid simply a weak or partial metal?