Modern smoke detectors utilize a small sample of americium-241 as a source of ionizing radiation. 241Am has a half-life of 432.2 years. The National Fire Protection Agency recommends replacing smoke detectors every 10 years. (a) How much 241Am remains after 10.0 years if a particular smoke detector contains 0.23 µg of 241Am at the time of construction?

Connection Terminated.

I am sorry to interrupt you, but I'm afraid you've been misinformed.

You are not here to receive a gift. Nor have you been called here by the individual you assume, although you have, indeed, been called.

You have all been called here. Into a labyrinth of sounds and smells, misdirection, and misfortune.

A labyrinth with no exit.

A maze with no prize.

You don't even realize that you are trapped.

Your lust for blood has driven you in endless circles, chasing the cries of children in some unseen chamber, always seeming so near, yet somehow out of reach. But you will never find them.

None of you will.

This is where your story ends.

And to you, my brave volunteer, who somehow found this job listing not intended for you. Although there was a way out planned for you, I have a feeling that's not what you want. I have a feeling that you are right where you want to be.

I am remaining as well.

I am nearby.

This place will not be remembered, and the memory of everything that started this can finally begin to fade away, as the agony of every tragedy should.

And to you monsters trapped in the corridors, be still and give up your spirit. They don't belong to you. For most of you, I believe there is peace and perhaps more waiting for you after the smoke clears.

Although, for one of you, the darkest pit of Hell has opened to swallow you whole, so don't keep the devil waiting, old friend.

My daughter, if you can hear me, I knew you would return as well. It's in your nature to protect the innocent. I'm sorry that on that day, the day you were shut out and left to die, no one was there to lift you up into their arms the way you lifted others into yours. And then, what became of you. I should've known you wouldn't be content to disappear. Not my daughter. I couldn't save you then... so let me save you now. It's time to rest... for you, and for those you have carried in your arms. This ends for all of us.

End Communication.

alkaline metals are lithium, sodium, rubidium, potassium, cesium and francium.

alkali metals have electronegativity from 0.7 to 1, lowest in periodic table of elements, which means that alkali metals (i group in periodic table) has positive oxidation number in compounds.

electronegativity is a chemical property that describes the tendency of an atom to attract a shared pair of electrons towards itself.

alkaline metals (far left in main group) have lowest ionizations energy and easy remove valence electrons,

for example, potassium is the alkali metal and has a single valence electron in the outer electron shell.

electron configuration of potassium is: ₁₉k 1s²2s²2p⁶3s²3p⁶4s¹.

they can not exist alone in nature, because they are very reactive.