Which of the following characteristics indicates that an atom is unstable? A. A full valence shell
B. Forming very strong bonds
C. Existing by itself
D. Low electronegativity

D

Explanation:

An atom can be considered unstable in one or two ways. If it pickes up or loses an electron,it becomes electrically charged and highly reactive.Intabability can also occur in the nucleus when the number of protons and neutrons is unbalanced.

the answer is A full valence shell

Explanation:

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