For example Cretaceous–Paleogene extinction event approximately 66 million years ago led to extinction<span> of approximately three quarters of the plant and animal in Earth. Dinosaurs extinct, but mammals adopt to new conditions and soon becaome one of the largest group in Earth.</span> Temperature drops unnaturaly in Earth's atmosphere. <span> This catastrophe end of the </span>Cretaceous<span> and entire </span>Mesozoic <span>Era and start the </span>Cenozoic<span> Era.</span>
Answer: Heyo Kenji Here! Here's your answer- Mg =1s2 2s2 2p6 3s2 = [Ne]3s2, therefore magnesium has 10 core electrons from its 1s2, 2s2, 2p6 orbitals. Magnesium is element 12, so it has 12 protons and a nuclear charge of 12.
Explanation: Hope this helps!
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- Kenji ^^