When did the level of oxygen in earth's atmosphere become high enough to sustain aerobic respiration? when did the level of oxygen in earth's atmosphere become high enough to sustain aerobic respiration? 3.5 billion years ago 1.5 billion years ago 2.7 billion years ago 1.0 billion years ago

they it depends on if one believes about radioactivity, they make a geiger counter beep but maybe it was going to beep anyway electronics do wierd things all the time or it was programmed to beep near certain metals.

yes

ya te ayud espera

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8