Mixture. Mixtures can be separated into their component parts, while substances are chemically bonded atoms that can't be separated by physical means.
Answer:

Explanation:
Hello there!
In this case, since the radioactive reaction for the alpha emission of astatine-218 to bismith-214 involve the release of a helium atom as shown below:

Whereas the atomic number decreases by 2 and the mass number by 4 in agreement to the release of the Helium atom.
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Answer:
Cs
Explanation:
This element is the farthest right, and lowest meaning that the reactivity of it is very high.
1. valence electrons and electronegativity
2. Both reactivity and electronegativity decrease down a group.
3. Electronegativity decreases down a group, and reactivity increases down a group.
4. The number of valence electrons increases from left to right.
5. Cs
{quizlet: captncrun}
Answer:
B
Explanation:
I think that's it.. hope I helped you