ch.2 elements found in living systems

Question 1

valence electrons and valence shell

Answer 1

valence electrons: interactions of the electrons in the outermost energy level.

valence shell: can contain no more than either electrons.

Question 2

octet rule

Answer 2

rule of eight: atoms tend to establish completely full outer energy levels.
-> one filled s orbital and three filled p orbitals.

Question 3

12 most common in living systems + atomic numbers less than ___

Answer 3

(O, C, H, N, P, S, Na, K, Ca, Mg, Fe, Cl)

(oxygen, carbon, hydrogen, nitrogen, phosphorous, sulfur, sodium, potassium, calcium, magnesium, iron, chlorine)

these elements all have atomic numbers less than 21, thus low atomic masses.