I wonder how much of an element collection you could build up if you're fine with compounds and you take only common-ish objects

Hydrogen: Pick a hydrocarbon, any hydrocarbon
Helium: ??
Lithium: -ion battery
Beryllium: ??
Boron: Silly putty? Neodymium magnet?
Carbon: graphite
Nitrogen: Air
Oxygen: More air (or water)
Fluorine: Toothpaste?
Neon: A neon lamp
Sodium: Table salt
Calcium: Chalk
Aluminum: can
Silicon: Electronics
Phosphorus: ??
Sulfur: Just pure sulfur??
Chlorine: More salt (/clorox)

@Felthry You skipped magnesium (calcium comes after potassium, not sodium), which you could get from sparklers or those fancy magnesium-alloy car wheels.

Bleach would be good for chlorine as well, as you were trying to fit into the 500 character limit earlier.

@Felthry And now that I'm thinking about this, I'll continue it:

Argon: (isn't there a type of lightbulb that's filled with argon?)
Potassium: Sodium-free salt
Calcium: Chalk, like you said
Scandium: ???
Titanium: Probably some expensive pen or jewelry
Vanadium: ??
Chromium: Stainless steel silverware
Manganese: Manganese dioxide from a battery
Iron: Paperclip
Cobalt: Wasn't there a cobalt-based audiotape formulation?
Nickel: Most coinage contains nickel, iirc
Copper: wire
Zinc: galvanized nail

@Felthry
Gallium: a gallium arsenide electronic component?
Germanium: a very old electronic component
Arsenic: Another sample of gallium arsenide
Selenium: A selenium rectifier
Bromine: ??
Krypton: ?? (joke answer: action figure of superman)
Rubidium: might have to go with a rubidium clock for this one
Strontium: ??
Yttrium: ??
Zirconium: Fake diamond?
Niobium: Niobium capacitor?
Molybdenum: ??
Technetium: ❌
Ruthenium: too expensive
Rhodium: also expensive
Palladium: PdC catalyst?
Silver: ware

@Felthry
Cadmium: NiCd battery
Indium: Galinstan?
Tin: coins, anything bronze
Antimony: ??
Tellurium: ??
Iodine: iodized salt
Xenon: ?? (xenon arc lamps are too expensive)
Cesium: Some vacuum tubes used a caesium-alloy cathode
Barium: ??
Lanthanum: ??
Cerium: the "flint" of a flint-and-steel
Praseodymium: ??
Neodymium: magnet
Promethium: ??
Samarium: ??
Europium: ??
Gadolinium: ??
Terbium: ??
Dysprosium: ??
Holmium: ??
Erbium: Optical fiber equipment?
Thulium: ??
Ytterbium: ??
Lutetium: ??

@Felthry Clearly, lanthanides are hard to place.

Hafnium: ??
Tantalum: capacitor
Tungsten: lightbulb, tungsten carbide tool
Rhenium: ??
Osmium: ??
Iridium: Expensive fountain pens
Platinum: Catalytic converter out of a car
Gold: Jewelry
Mercury: Old thermometer
Thallium: ??
Lead: Old paint
Bismuth: Pepto-bismol

And everything after that is radioactive.

@Rosemary @Felthry Americium from most smoke detectors, thorium from those weird socks that go on camp lanterns

@VoxSomniator @Rosemary Yeah, but we were only going for the stable ones.

Pretty sure dismantling smoke detectors and extracting the americium would get you on some kind of watchlist

@Felthry @Rosemary Yeah, both of these items got someone in trouble for trying to build a tiny nuclear generator...

@VoxSomniator @Rosemary Completely off topic, have I mentioned that your icon is adorable?

@Felthry @Rosemary :D I'm not sure exactly who you meant but everyone here has adorable avatars so thanks!

@VoxSomniator @Rosemary Oh I meant you, sorry! Rose's icon is cute too though!