Calcium (ca) has an atomic number of 20. what is calcium's ground-state electron configuration? 1s21p61d101f2 1s21p62s22p63s23p2 1s22s22p63s23p64s2 1s22s22p63s23p63d2

I belive the answer is C. 1s2 2s2 2p6 3s2 3p6 4s2

Electron configuration are used to tell the distribution of electrons of an atom or molecule. The electron configuration order should follow a specific path. You will found some similarity of the rule with the number of row in the periodic table. After the electrons fill 3P, the electron should fill 4S before it go to 3D.

answer: - b cells

explanation: -

so, the b cells mediate their action by identifying the antigens present on the surface of the pathogens and then producing antibodies in return to mediate its effect.

i believe it is "they are not used up by reactions" as the answer to your question, text me back if this is correct because i just learned this.