Elemental

Osmium is very dense, blocks of osmium fall, smashing the ground damaging entities and a whole ore only gives you a few nuggets. You can even use it to craft a new weapon with it's own unique enchantments and behaviour, the Osmium Warhammer. It can also be used to smith iron armour into an alloy with high knockback resistance, its tradeoff is that it makes you fall faster. This element can find the ore in taiga biomes.

Lithium is more an allegory for all group 1 elements; it's extracted from salt blocks found in deserts, it will start fizzing before exploding if the block contacts water, is used to make bleach powder for undying things (e.g. stained glass into normal glass) and can be crafted into batteries which give off a constant redstone signal.

Tungsten is very tough, found in mountains and in real life is used to make filament bulbs; I based it's properties around luminosity because of that and so far it adds a handful of interesting new light sources but isn't quite finished.

Germanium refracts light very well and is used to make optic cable, a redstone alternative that can be activated with light sources up to 24 blocks away in a straight line to power any blocks with solid sides, grab a redstone lamp and play around with it. The most obvious use is vertically sending redstone signals so if you want some, large but rare veins of ore can be found underneath birch forest biomes.

Helium is the second lightest element so its properties are based around floaty-ness; after searching the sides of end islands for 'bubbled endstone' and breaking the block, you'll need a bottle to capture the bubble that spawns, be fast or else it'll just keep floating upwards out of reach... Drink bottles of helium to levitate, use them to craft some anti-gravity projectiles and combine them with iron to make a new chestplate which gives you some mobility buffs. Finally, you can craft 4 bottles of helium together to make a helium block, it acts like an item/mob elevator but it'll evaporate into helium bubbles if there's no block above it and no ice (to keep it cool) around it!

Neodymium is used in real life to make super magnets, I took some creative liberties and made a magnetic resource whose ore and block form pull all entities (items & mobs too) towards it. While rare, you'll find neodymium ore up to y = 20 in the overworld, as you uncover stone around it you may notice the cobble move to one side of your strip mine, being attracted by a neodymium ore vein (they get more attractive at closer distances). Use neodymium with tungsten and redstone to craft an electromagnet; these function a little differently to the ores as they are redstone controlled and attract entities in only one direction with a constant strength. Combine an electromagnet with helium to get a cooled electromagnet which can push entities directionally. All magnets affect iron and netherite items and entities (if it has the material name as the prefix or is made entirely out of the material) with greater strength.